Phenazine-based non-fullerene acceptors(NFAs)have demonstrated great potential in improving the power conversion efficiency(PCE)of organic solar cells(OSCs).Halogenation is known to be an effective strategy for increa...Phenazine-based non-fullerene acceptors(NFAs)have demonstrated great potential in improving the power conversion efficiency(PCE)of organic solar cells(OSCs).Halogenation is known to be an effective strategy for increasing optical absorption,refining energy levels,and improving molecular packing in organic semiconductors.Herein,a series of NFAs(Pz IC-4H,Pz IC-4F,Pz IC-4Cl,Pz IC-2Br)with phenazine as the central core and with/without halogen-substituted(dicyanomethylidene)-indan-1-one(IC)as the electron-accepting end group were synthesized,and the effect of end group matched phenazine central unit on the photovoltaic performance was systematically studied.Synergetic photophysical and morphological analyses revealed that the PM6:Pz IC-4F blend involves efficient exciton dissociation,higher charge collection and transfer rates,better crystallinity,and optimal phase separation.Therefore,OSCs based on PM6:Pz IC-4F as the active layer exhibited a PCE of 16.48%with an open circuit voltage(Voc)and energy loss of 0.880 V and 0.53 e V,respectively.Accordingly,this work demonstrated a promising approach by designing phenazine-based NFAs for achieving high-performance OSCs.展开更多
Organic solar cells(OSCs)processed without halogenated solvents and complex treatments are essential for future commercialization.Herein,we report three novel small molecule acceptors(NFAs)consisting of a Y6-like core...Organic solar cells(OSCs)processed without halogenated solvents and complex treatments are essential for future commercialization.Herein,we report three novel small molecule acceptors(NFAs)consisting of a Y6-like core but withπ-extended naphthalene with progressively more chlorinated end-capping groups and a longer branched chain on the Nitrogen atom.These NFAs exhibit good solubilities in nonchlorinated organic solvents,broad optical absorptions,closeπ-πstacking distances(3.63–3.84A),and high electron mobilities(~10^(-3)cm^(2)V^(-1)s^(-1)).The o-xylene processed and as-cast binary devices using PM6 as the donor polymer exhibit a PCE increasing upon progressive chlorination of the naphthalene end-capping group from 8.93%for YN to 14.38%for YN-Cl to 15.00%for YN-2Cl.Furthermore similarly processed ternary OSCs were fabricated by employing YN-Cl and YN-2Cl as the third component of PM6:CH1007 blends(PCE=15.75%).Compared to all binary devices,the ternary PM6:CH1007:YN-Cl(1:1:0.2)and PM6:CH1007:YN-2Cl(1:1:0.2)cells exhibit significantly improved PCEs of 16.49%and15.88%,respectively,which are among the highest values reported to date for non-halogenated solvent processed OSCs without using any additives and blend post-deposition treatments.展开更多
A rational design of efficient low-band-gap non-fullerene acceptors(NFAs)for high-performance organic solar cells(OSCs)remains challenging;the main constraint being the decrease in the energy level of the lowest unocc...A rational design of efficient low-band-gap non-fullerene acceptors(NFAs)for high-performance organic solar cells(OSCs)remains challenging;the main constraint being the decrease in the energy level of the lowest unoccupied molecular orbitals(LUMOs)as the bandgap of A-D-A-type NFAs decrease.Therefore,the short current density(J_(sc))and open-circuit voltage(V_(oc))result in a trade-off relationship,making it difficult to obtain efficient OSCs.Herein,three NFAs(IFL-ED-4 F,IDT-ED-4 F,and IDTT-ED-2 F)were synthesized to address the above-mentioned issue by introducing 3,4-ethylenedioxythiophene(EDOT)as aπ-bridge.These NFAs exhibit relatively low bandgaps(1.67,1.42,and 1.49 eV,respectively)and upshifted LUMO levels(-3.88,-3.84,and-3.81 eV,respectively)compared with most reported low-band-gap NFAs.Consequently,the photovoltaic devices based on IDT-ED-4 F blended with a PBDB-T donor polymer showed the best power conversion efficiency(PCE)of 10.4%with a high J_(sc) of 22.1 mA cm^(-2) and Voc of 0.884 V among the examined NFAs.In contrast,IDTT-ED-4 F,which was designed with an asymmetric structure of the D-p-A type,showed the lowest efficiency of 1.5%owing to the poor morphology and charge transport properties of the binary blend.However,when this was introduced as the third component of the PM6:BTP-BO-4 Cl,complementary absorption and cascade energy-level alignment between the two substances could be achieved.Surprisingly,the IDTT-ED-4 F-based ternary blend device not only improved the Jscand Voc,but also achieved a PCE of 15.2%,which is approximately 5.3%higher than that of the reference device with a minimized energy loss of 0.488 eV.In addition,the universality of IDTT-ED-2 F as a third component was effectively demonstrated in other photoactive systems,specifically,PM6:BTPe C9 and PTB7-Th:IEICO-4 F.This work facilitates a better understanding of the structure–property relationship for utilizing efficient EDOT-bridged NFAs in high-performance OSC applications.展开更多
Two acceptor-donor-acceptor(A-D-A)type non-fullerene acceptors(namely WH1 and WH7)containing the oxindole-based bridge are designed and synthesized for polymer solar cells(PSCs)applications.The bridge unit is introduc...Two acceptor-donor-acceptor(A-D-A)type non-fullerene acceptors(namely WH1 and WH7)containing the oxindole-based bridge are designed and synthesized for polymer solar cells(PSCs)applications.The bridge unit is introduced through a precursor(6-bromo-1-octylindoline-2,3-dione)that contains both bromine and carbonyl and provides the feasibility of the Pd-catalyzed cross-coupling reaction and the Knoevenagel condensation,respectively.This facile synthetic approach exhibits the potential to gain high performance non-fullerene acceptors through extendingπ-conjugated backbone with strong light-absorbing building blocks.The synthesis and properties of WH1 and WH7 are demonstrated with different endcap units,then PSCs are fabricated using PBDB-T:WH1 and PBDB-T:WH7 as the active layers,and attain an average power conversion efficiency(PCE)of 2.58%and 6.24%,respectively.Further device physics studies afford the deep insight of structure variation influence on the device performance.This work provides a facile non-fullerene acceptor design strategy and shows how structure variations impact the PSC performance.展开更多
During last decade,organic photovoltaics experienced an exciting renaissance[1-5],mainly benefiting from the development of non-fullerene acceptors(NFAs),which boosted the power conversion efficiency to-20%[6,7].Along...During last decade,organic photovoltaics experienced an exciting renaissance[1-5],mainly benefiting from the development of non-fullerene acceptors(NFAs),which boosted the power conversion efficiency to-20%[6,7].Along with the unprecedented success of organic solar cells,non-fullerene acceptors also find other optoelectronic applications.In particular,high-performance organic photodetectors(OPDs)[8,9]based on non-fullerene acceptors have been reported.展开更多
The selection of photoactive layer materials for organic solar cells(OSCs) is essential for the photoelectric conversion process.It is well known that chlorophyll is an abundant pigment in nature and is extremely valu...The selection of photoactive layer materials for organic solar cells(OSCs) is essential for the photoelectric conversion process.It is well known that chlorophyll is an abundant pigment in nature and is extremely valuable for photosynthesis.However,there is little research on how to improve the efficiency of chlorophyll-based OSCs by matching chlorophyll derivatives with excellent non-fullerene acceptors to form heterojunctions.Therefore in this study we utilize a chlorophyll derivative,Ce_(6)Me_(3),as a donor material and investigate the performance of its heterojunction with acceptor materials.Through density functional theory,the photoelectric performances of acceptors,i ncluding the fullerene derivative PC_(71)BM and the terminal halogenated non-fullerene DTBCIC series,are compared in detail.It is found that DTBCIC-C1 has better planarity,light absorption,electron affinity,charge reorganization energy and charge mobility than others.Ce_(6)Me_(3) has good energy level matching and absorption spectral complementarity with the investigated acceptor molecules and also shows good electron donor properties.Furthermore,the designed Ce_(6)Me_(3)/DTBCIC interfaces have improved charge separation and reorganization rates(K_(CS)/K_(CR)) compared with the Ce_(6)Me_(3)/PC_(71)BM interface.This research provides a theoretical basis for the design of photoactive layer materials for chlorophyll-based OSCs.展开更多
Since the world-record power conversion efficiency of 15.7%was achieved for organic solar cells(OSCs)in 2019,the newly developed non-fullerene acceptor(NFA)Y6 with an A-DA′D-A structure(A denotes an electron-acceptin...Since the world-record power conversion efficiency of 15.7%was achieved for organic solar cells(OSCs)in 2019,the newly developed non-fullerene acceptor(NFA)Y6 with an A-DA′D-A structure(A denotes an electron-accepting moiety,D denotes an electron-donating moiety)has attracted increasing attention.Subsequently,many new A-DA′D-A NFAs have been designed and synthesized,and the A-DA′D-A NFAs have played a significant role in the development of high-performance non-fullerene organic solar cells(NF-OSCs).Compared with the classical A-D-A-type acceptors,A-DA′D-A NFAs contain an electrondeficient core(such as benzothiadiazole(BT),benzotriazole(BTA),quinoxaline(Qx),or their derivatives)in the ladder-type fused rings to fine-tune the energy levels,broaden light absorption and achieve higher electron mobility of the NFAs.This review emphasizes the recent progress on these emerging A-DA′D-A(including Y-series)NFAs.The synthetic methods of DA′D-fused rings are introduced.The relationships between the chemical structure of the A-DA′D-A NFAs and the photovoltaic performance of the corresponding OSCs are summarized and discussed.Finally,issues and prospects for further improving photovoltaic performance of the OSCs are also proposed.展开更多
Side-chain engineering has been demonstrated as an effective method for fine-tuning the optical,electrical,and morphological properties of organic semiconductors toward efficient organic solar cells(OSCs).In this work...Side-chain engineering has been demonstrated as an effective method for fine-tuning the optical,electrical,and morphological properties of organic semiconductors toward efficient organic solar cells(OSCs).In this work,three isomeric non-fullerene small molecule acceptors(SMAs),named as BTP-4F-T2C8,BTP-4F-T2EH and BTP-4F-T3EH,with linear and branched alkyl chains substituted on the α or β positions of thiophene as the side chains,were synthesized and systematically investigated.The results demonstrate that the size and substitution position of alkyl side chains can greatly affect the electronic properties,molecular packing as well as crystallinity of the SMAs.After blending with donor polymer D18-Cl,the prominent device performance of 18.25% was achieved by the BTP-4F-T3EH-based solar cells,which is higher than those of the BTP-4F-T2EH-based(17.41%)and BTP-4F-T2C8-based(15.92%)ones.The enhanced performance of the BTP-4F-T3EH-based devices is attributed to its stronger crystallinity,higher electron mobility,suppressed bimolecular recombination,and the appropriate intermolecular interaction with the donor polymer.This work reveals that the side chain isomerization strategy can be a practical way in tuning the molecular packing and blend morphology for improving the performance of organic solar cells.展开更多
Recently,polymer solar cells developed very fast due to the application of non-fullerence acceptors.Substituting asymmetric small molecules for symmetric small molecule acceptors in the photoactive layer is a strategy...Recently,polymer solar cells developed very fast due to the application of non-fullerence acceptors.Substituting asymmetric small molecules for symmetric small molecule acceptors in the photoactive layer is a strategy to improve the performance of polymer solar cells.The asymmetric design of the molecule is very beneficial for exciton dissociation and charge transport and will also fine-tune the molecular energy level to adjust the open-circuit voltage(Voc)further.The influence on the absorption range and absorption intensity will cause the short-circuit current density(Jsc)to change,resulting in higher device performance.The effect on molecular aggregation and molecular stacking of asymmetric structures can directly change the microscopic morphology,phase separation size,and the active layer's crystallinity.Very recently,thanks to the ingenious design of active layer materials and the optimization of devices,asymmetric non-fullerene polymer solar cells(A-NF-PSCs)have achieved remarkable development.In this review,we have summarized the latest developments in asymmetric small molecule acceptors(A-NF-SMAs)with the acceptor-donor-acceptor(A-D-A)and/or acceptor-donor-acceptor-donor-acceptor(A-D-A-D-A)structures,and the advantages of asymmetric small molecules are explored from the aspects of charge transport,molecular energy level and active layer accumulation morphology.展开更多
For non-fullerene acceptors(NFAs)with linear A_(2)-A_(1)-D-A_(1)-A_(2) backbone,there are three kinds of possible intermolecular interaction,A_(1)-A_(1),A_(1)-A_(2) and A_(2)-A_(2) stacking.Hence,it is a huge challeng...For non-fullerene acceptors(NFAs)with linear A_(2)-A_(1)-D-A_(1)-A_(2) backbone,there are three kinds of possible intermolecular interaction,A_(1)-A_(1),A_(1)-A_(2) and A_(2)-A_(2) stacking.Hence,it is a huge challenge to control this interaction and investigate the effect of intermolecular stacking model on the photovoltaic performance.Here,we adopt a feasible strategy,by utilizing different substituent groups on terminal A2 unit of dicyanomethylene rhodanine(RCN),to modulate this stacking model.According to theoretical calculation results,the molecule BTA3 with ethyl substituent packs via heterogeneous interaction between A_(2) and A_(1) unit in neighboring molecules.Surprisingly,the benzyl group can effectively transform the aggregation of BTA5 into homogeneous packing of A_(2)-A_(2) model,which might be driven by the strong interaction between benzyl and A1(benzotriazole)unit.However,different with benzyl,phenyl end group impedes the intermolecular interaction of BTA4 due to the large steric hindrance.When using a BTA-based D-π-A polymer J52-F as donor according to“Same-A-Strategy”,BTA3-5 could achieve ultrahigh open-circuit voltage(VOC)of 1.17–1.21 V.Finally,BTA5 with benzyl groups realized an improved power conversion efficiency(PCE)of 11.27%,obviously higher than that of BTA3(PCE=9.04%)and BTA4(PCE=5.61%).It is also worth noting that the same trend can be found when using other four classic p-type polymers of P3HT,PTB7,PTB7-Th and PBDB-T.This work not only investigates the intermolecular interaction of A_(2)-A_(1)-D-A_(1)-A_(2) type NFAs for the first time,but also provides a straightforward and universal method to change the interaction model and improve the photovoltaic performance.展开更多
Side chain engineering plays a substantial role for high-performance organic solar cells (OSCs).Herein,a series of non-fullerene acceptor (NFA) molecules with A-D-A structures,TTCn-4F,with gradient substituent lengths...Side chain engineering plays a substantial role for high-performance organic solar cells (OSCs).Herein,a series of non-fullerene acceptor (NFA) molecules with A-D-A structures,TTCn-4F,with gradient substituent lengths of terminal side chains (T-SCs) on the molecular backbones have been designed and synthesized.The effects of T-SCs length,ranging from hydrogen atom to n-dodecyl,their optoelectronic properties,thin film molecular packing,blend film morphology,and overall photovoltaic performance have been systematically studied.The results show that among this series of molecules,TTC8-4F with n-octyl substituent,showed the best photovoltaic performance when applied with PM6 as the donor due to its favorable morphology,balanced charge mobility,effective exciton dissociation and less charge recombination.Based on this,its ternary device with F-Br as the secondary acceptor achieved a high PCE of 15.34%with the simultaneously enhanced Voc of 0.938 V,Jscof 22.66 mA cm^-2,and FF of 72.15%.These results indicate that the engineering of T-SCs is an effective strategy for designing high-performance NFAs.展开更多
To achieve the red-shifted absorptions and appropriate energy levels of A-D-A type non-fullerene acceptors(NFAs), in this work, we design and synthesize two new NFAs, named TPDCIC and TPDCNC, whose electron-donating(D...To achieve the red-shifted absorptions and appropriate energy levels of A-D-A type non-fullerene acceptors(NFAs), in this work, we design and synthesize two new NFAs, named TPDCIC and TPDCNC, whose electron-donating(D) unit is constructed by a thieno[3,4-c]pyrrole-4,6-dione(TPD) core attached to two cyclopentadithiophene(CPDT) moieties at both sides, and the electronaccepting(A) end-groups are 2-(3-oxo-2,3-dihydroinden-1-ylidene)malononitrile(IC) and 2-(3-oxo-2,3-dihydro-1 H-cyclopenta[b]naphthalen-1-ylidene)malononitrile(NC), respectively. Benefiting from TPD core, which easily forms quinoid structure and O···H or O···S intramolecular noncovalent interactions, TPDCIC and TPDCNC show more delocalization of π-electrons and perfect planar molecular geometries, giving the absorption ranges extended to 822 and 852 nm, respectively. Furthermore, the highest occupied molecular orbital(HOMO) levels of TPDCIC and TPDCNC remain relatively low-lying due to the electronegativity of the carbonyl groups on TPD core. Considering that the absorptions and energy levels of the two NFAs match well with those of a widely used polymer donor, PBDB-T, we fabricate two kinds of organic solar cells(OSCs) based on the PBDB-T:TPDCIC and PBDB-T:TPDCNC blended films, respectively. Through a series of optimizations, the TPDCIC-based devices yield an impressing power conversion efficiency(PCE)of 10.12% with a large short-circuit current density(JSC) of 18.16 mA·cm-2, and the TPDCNC-based ones exhibit a comparable PCE of9.80% with a JSC of 17.40 mA·cm-2. Our work is the first report of the TPD-core-based A-D-A type NFAs, providing a good reference for the molecular design of high-performance NFAs.展开更多
Recently, perylene diimide (PDI) derivatives were attractive as the electron-deficient acceptor materials in non-fullerene organic solar cells since Tang first used a single PDI compound as the n-type semiconductor ...Recently, perylene diimide (PDI) derivatives were attractive as the electron-deficient acceptor materials in non-fullerene organic solar cells since Tang first used a single PDI compound as the n-type semiconductor to fabricate photovoltaic devices in 1986, which achieved a power conversion efficiency of 1%. Beside the monomeric PDIs, the linear and three dimensional (3D) PDl-based small molecular acceptors have also made great achievements with the power conversion efficiencies over 9.0% in single- junction polymer solar cells, and over 10.0% in tandem solar cells. The excellent device performance can be realized by forming suitable twisted structure, developing suitable donor materials and optimizing device technologies. In this review, we summarize the recent development of PDl-based small molecular non-fullerene acceptors in non-fullerene organic solar cells, including molecular design strategies and structure-property relationships.展开更多
Fullerenes and their derivatives are important types of electron acceptor materials and play a vital role in organic solar cell devices. However, the fullerene acceptor material has some difficulties to overcome the i...Fullerenes and their derivatives are important types of electron acceptor materials and play a vital role in organic solar cell devices. However, the fullerene acceptor material has some difficulties to overcome the intrinsic shortcomings, such as weak absorption in the visible range, difficulty in modification and high cost, which limit the performance of the device and the large-scale application of this type of acceptors. In recent years, non-fullerene electron acceptor material has attracted the attention of scientists due to the advantages of adjustable energy level, wide absorption, simple synthesis, low processing cost and good solubility. Researchers can use the rich chemical means to design and synthesize organic small molecules and their oligomers with specific aggregation morphology and excellent optoelectronic prop- erties. Great advances in the field of synthesis, device engineering, and device physics of non-fullerene acceptors have been achieved in the last few years. At present, non-fullerene small molecules based photovoltaic devices achieve the highest efficiency more than 13% and the efficiency gap between fullerenetype and non-fullerene-type photovoltaic devices is gradually narrowing. In this review, we explore recent progress of non-fullerene small molecule electron acceptors that have been developed and led to highefficiency photovoltaic devices and put forward the prospect of development in the future.展开更多
Summary of main observation and conclusion The ternary blend structure has been demonstrated as an effective approach to increase the power conversion efficiency of organic solar cells.An effective approach to enhance...Summary of main observation and conclusion The ternary blend structure has been demonstrated as an effective approach to increase the power conversion efficiency of organic solar cells.An effective approach to enhance the power conversion efficiency of ternary solar cells is based on two non-fullerene acceptors with complimentary absorption range and balanced crystallinity.In this work,we have introduced a high crystallinity small-molecule acceptor,named C8IDTT-4CI with appropriate alkyl side chains into a low crystalline blend of conjugated polymer donor PBDT-TPD and fused-ring electron acceptor ITIC-4F.A ternary device based on the blend PBDT-TPD:1TIC-4F:C81DTT-4CI exhibits a best power conversion efficiency of 9.51%with a simultaneous improvement of the short-circuit current density to 18.76 mA-cm^-2 and the fill factor up to 67.53%.The absorption onset for C8IDTT-4CI is located at 900 nm,so that the well complementary light absorption is beneficial to the photocurrent.In addition,the existence of high crystallinity C8IDTT-4CI in the ternary device is found helpful to modulate crystallinity,improve heterojunction morphologies and stacking structure,therefore to realize higher charge mobility and better performance.展开更多
Non-fullerene polymer solar cells(NF-PSCs) have gained wide attention recently. Molecular design of non-fullerene electron acceptors effectively promotes the photovoltaic performance of NF-PSCs. However,molecular elec...Non-fullerene polymer solar cells(NF-PSCs) have gained wide attention recently. Molecular design of non-fullerene electron acceptors effectively promotes the photovoltaic performance of NF-PSCs. However,molecular electron acceptors with 2-dimensional(2 D) configuration and conjugation are seldom reported.Herein, we designed and synthesized a series of novel 2 D electron acceptors for efficient NF-PSCs. With rational optimization on the conjugated moieties in both vertical and horizontal direction, these 2 D electron acceptors showed appealing properties, such as good planarity, full-spectrum absorption, high absorption extinction coefficient, and proper blend morphology with donor polymer. A high PCE of 9.76%was achieved for photovoltaic devices with PBDB-T as the donor and these 2 D electron acceptors. It was also found the charge transfer between the conjugated moieties in two directions of these 2 D molecules contributes to the utilization of absorbed photos, resulting in an exceptional EQE of 87% at 730 nm. This work presents rational design guidelines of 2 D electron acceptors, which showed great promise to achieve high-performance non-fullerene polymer solar cells.展开更多
Side-chain engineering has been considered as one of the most promising strategies to optimize non-fullerene small-molecule acceptors(NFSMAs).Previous efforts were focused on the optimization of alkyl-chain length,sha...Side-chain engineering has been considered as one of the most promising strategies to optimize non-fullerene small-molecule acceptors(NFSMAs).Previous efforts were focused on the optimization of alkyl-chain length,shape,and branching sites.In this work,we propose that asymmetric side-chain engineering can effectively tune the properties of NFSMAs and improve the power conversion efficiency(PCE)for binary non-fullerene polymer solar cells(NFPSCs).Specifically,by introducing asymmetric side chains into the central core,both of the absorption spectra and molecule orientation of NFSMAs are efficiently tuned.When blended with polymer donor PM6,NFPSCs with EH-HD-4F(2-ethylhexyl and 2-hexyldecyl side chains)demonstrate a champion PCE of 18.38%with a short-circuit current density(J_(SC))of 27.48 mA cm^(-2),an open circuit voltage(V_(OC))of 0.84 V,and a fill factor(FF)of 0.79.Further studies manifest that the proper asymmetric side chains in NFSMAs could induce more favorable face-on molecule orientation,enhance carrier mobilities,balance charge transport,and reduce recombination losses.展开更多
Non-fullerene organic solar cells have received increasing attentions in these years,and great progresses have been made since 2013.Among them,aromatic di-amide/imide-containing frameworks have shown promising applica...Non-fullerene organic solar cells have received increasing attentions in these years,and great progresses have been made since 2013.Among them,aromatic di-amide/imide-containing frameworks have shown promising applications.The outstanding properties of them are highly associated with their unique electronic and structural features,such as strong electron-withdrawing nature,broad absorption in UVvisible region,tunable HOMO/LUMO energy levels,easy modifications,and excellent chemical,thermal and photochemical stabilities.In this review,we give an overview of recent developments of aromatic diamide/imide-containing small molecules used as electron acceptors for organic solar cells.展开更多
Two novel non-fullerene small molecule acceptors were prepared with the conjugated backbone of 5 H-fluoreno[3, 2-b:6, 7-b’] dithiophene carrying the electron deficient unit of dicyanomethylene indanone(DICTFDT) and r...Two novel non-fullerene small molecule acceptors were prepared with the conjugated backbone of 5 H-fluoreno[3, 2-b:6, 7-b’] dithiophene carrying the electron deficient unit of dicyanomethylene indanone(DICTFDT) and rhodanine(TFDTBR), respectively. The two acceptors exhibited excellent thermal stability and strong absorption in the visible region. The LUMO level is estimated to be at-3.89 eV for DICTFDT and-3.77 eV for TFDTBR. When utilized as the acceptor in bulk heterojunction polymer solar cells with the polymer donor of PBT7-Th, the optimized maximum power conversion efficiency of 5.12% and 3.95% was obtained for the device with DICTFDT and TFDTBR, respectively. The research demonstrates that 5 H-fluoreno[3, 2-b:6, 7-b’] dithiophene can be an appealing candidate for constructing small molecular electron acceptor towards efficient polymer:non-fullerene bulk heterojunction solar cells.展开更多
A series of novel wide bandgap small molecules(IFT-ECA, IFT-M, IFT-TH and IFT-IC) based on the A-D-A structure with indenofluorene core, thiophene bridge, and different electron-deficient end-capping groups, were synt...A series of novel wide bandgap small molecules(IFT-ECA, IFT-M, IFT-TH and IFT-IC) based on the A-D-A structure with indenofluorene core, thiophene bridge, and different electron-deficient end-capping groups, were synthesized and used as non-fullerene acceptors in organic solar cells. The influences of end-capping groups on the device performance were studied.The four materials exhibited different physical and chemical properties due to the variation of end-capping groups, which further affect the exciton dissociation, charge transport, morphology of the bulk-heterojunction films and device performance. Among them, IFT-IC-based device delivered the best power conversion efficiency of 7.16% due to proper nano-scale phase separation morphology and high electron mobility, while the devices based on the other acceptors achieved lower device performance(4.14% for IFT-TH, <1% for IFT-ECA and IFT-M). Our results indicate the importance of choosing suitable electron-withdrawing groups to construct high-performance non-fullerene acceptors based on A-D-A motif.展开更多
基金financially supported by the National Natural Science Foundation of China (22279152,U21A20331)the National Science Fund for Distinguished Young Scholars (21925506)+1 种基金the Ningbo key scientific and technological project (2022Z117)the Ningbo Natural Science Foundation (2021J192)。
文摘Phenazine-based non-fullerene acceptors(NFAs)have demonstrated great potential in improving the power conversion efficiency(PCE)of organic solar cells(OSCs).Halogenation is known to be an effective strategy for increasing optical absorption,refining energy levels,and improving molecular packing in organic semiconductors.Herein,a series of NFAs(Pz IC-4H,Pz IC-4F,Pz IC-4Cl,Pz IC-2Br)with phenazine as the central core and with/without halogen-substituted(dicyanomethylidene)-indan-1-one(IC)as the electron-accepting end group were synthesized,and the effect of end group matched phenazine central unit on the photovoltaic performance was systematically studied.Synergetic photophysical and morphological analyses revealed that the PM6:Pz IC-4F blend involves efficient exciton dissociation,higher charge collection and transfer rates,better crystallinity,and optimal phase separation.Therefore,OSCs based on PM6:Pz IC-4F as the active layer exhibited a PCE of 16.48%with an open circuit voltage(Voc)and energy loss of 0.880 V and 0.53 e V,respectively.Accordingly,this work demonstrated a promising approach by designing phenazine-based NFAs for achieving high-performance OSCs.
基金supported by the National Natural Science Foundation of China(61804073)the Center for Light Energy Activated Redox Processes(LEAP),an Energy Frontier Research Center funded by the U.S.Department of Energy,Office of Science,Office of Basic Energy Sciences,under award DE-SC0001059+3 种基金the Mat CI Facility which receives support from the National Science Foundation MRSEC Program(NSF DMR-1720139)of the Materials Research Center at Northwestern Universitysupport from the US Office of Naval Research Contract N00014-20-1-2116the U.S.Department of Energy under contract No.DE-AC02-05CH11231at beamline 8-ID-E of the Advanced Photon Source,a U.S.Department of Energy(DOE)Office of Science User Facility operated for the DOE Office of Science by Argonne National Laboratory under Contract No.DE-AC0206CH11357。
文摘Organic solar cells(OSCs)processed without halogenated solvents and complex treatments are essential for future commercialization.Herein,we report three novel small molecule acceptors(NFAs)consisting of a Y6-like core but withπ-extended naphthalene with progressively more chlorinated end-capping groups and a longer branched chain on the Nitrogen atom.These NFAs exhibit good solubilities in nonchlorinated organic solvents,broad optical absorptions,closeπ-πstacking distances(3.63–3.84A),and high electron mobilities(~10^(-3)cm^(2)V^(-1)s^(-1)).The o-xylene processed and as-cast binary devices using PM6 as the donor polymer exhibit a PCE increasing upon progressive chlorination of the naphthalene end-capping group from 8.93%for YN to 14.38%for YN-Cl to 15.00%for YN-2Cl.Furthermore similarly processed ternary OSCs were fabricated by employing YN-Cl and YN-2Cl as the third component of PM6:CH1007 blends(PCE=15.75%).Compared to all binary devices,the ternary PM6:CH1007:YN-Cl(1:1:0.2)and PM6:CH1007:YN-2Cl(1:1:0.2)cells exhibit significantly improved PCEs of 16.49%and15.88%,respectively,which are among the highest values reported to date for non-halogenated solvent processed OSCs without using any additives and blend post-deposition treatments.
基金supported by the KU Research Professor Program of Konkuk Universitythe Korea Institute of Energy Technology Evaluation and Planning (KETEP)+1 种基金the Ministry of Trade, Industry & Energy (MOTIE) of the Republic of Korea (No. 20193091010110)a National Research Foundation of Korea (NRF) grant funded by the Korean government (MSIT) (No. 2020R1A2C201091611)。
文摘A rational design of efficient low-band-gap non-fullerene acceptors(NFAs)for high-performance organic solar cells(OSCs)remains challenging;the main constraint being the decrease in the energy level of the lowest unoccupied molecular orbitals(LUMOs)as the bandgap of A-D-A-type NFAs decrease.Therefore,the short current density(J_(sc))and open-circuit voltage(V_(oc))result in a trade-off relationship,making it difficult to obtain efficient OSCs.Herein,three NFAs(IFL-ED-4 F,IDT-ED-4 F,and IDTT-ED-2 F)were synthesized to address the above-mentioned issue by introducing 3,4-ethylenedioxythiophene(EDOT)as aπ-bridge.These NFAs exhibit relatively low bandgaps(1.67,1.42,and 1.49 eV,respectively)and upshifted LUMO levels(-3.88,-3.84,and-3.81 eV,respectively)compared with most reported low-band-gap NFAs.Consequently,the photovoltaic devices based on IDT-ED-4 F blended with a PBDB-T donor polymer showed the best power conversion efficiency(PCE)of 10.4%with a high J_(sc) of 22.1 mA cm^(-2) and Voc of 0.884 V among the examined NFAs.In contrast,IDTT-ED-4 F,which was designed with an asymmetric structure of the D-p-A type,showed the lowest efficiency of 1.5%owing to the poor morphology and charge transport properties of the binary blend.However,when this was introduced as the third component of the PM6:BTP-BO-4 Cl,complementary absorption and cascade energy-level alignment between the two substances could be achieved.Surprisingly,the IDTT-ED-4 F-based ternary blend device not only improved the Jscand Voc,but also achieved a PCE of 15.2%,which is approximately 5.3%higher than that of the reference device with a minimized energy loss of 0.488 eV.In addition,the universality of IDTT-ED-2 F as a third component was effectively demonstrated in other photoactive systems,specifically,PM6:BTPe C9 and PTB7-Th:IEICO-4 F.This work facilitates a better understanding of the structure–property relationship for utilizing efficient EDOT-bridged NFAs in high-performance OSC applications.
基金National Natural Science Foundation of China(No.21805032)Natural Science Foundation of Shanghai,China(No.19ZR1401400)Fundamental Research Funds for the Central Universities,China(No.20D128502).
文摘Two acceptor-donor-acceptor(A-D-A)type non-fullerene acceptors(namely WH1 and WH7)containing the oxindole-based bridge are designed and synthesized for polymer solar cells(PSCs)applications.The bridge unit is introduced through a precursor(6-bromo-1-octylindoline-2,3-dione)that contains both bromine and carbonyl and provides the feasibility of the Pd-catalyzed cross-coupling reaction and the Knoevenagel condensation,respectively.This facile synthetic approach exhibits the potential to gain high performance non-fullerene acceptors through extendingπ-conjugated backbone with strong light-absorbing building blocks.The synthesis and properties of WH1 and WH7 are demonstrated with different endcap units,then PSCs are fabricated using PBDB-T:WH1 and PBDB-T:WH7 as the active layers,and attain an average power conversion efficiency(PCE)of 2.58%and 6.24%,respectively.Further device physics studies afford the deep insight of structure variation influence on the device performance.This work provides a facile non-fullerene acceptor design strategy and shows how structure variations impact the PSC performance.
基金the financially supports from the National Natural Science Foundation of China (61875154)the National Natural Science Foundation of China (51922032, 21961160720)+4 种基金Wuhan Science and Technology Bureau (2022010801010108)the open research fund of Hubei Luojia Laboratory (220100042)the National Key Research and Development Program of China (2020YFB2008800)the open research fund of Songshan Lake Materials Laboratory (2021SLABFK02)the National Key Research and Development Program of China (2017YFA0206600).
文摘During last decade,organic photovoltaics experienced an exciting renaissance[1-5],mainly benefiting from the development of non-fullerene acceptors(NFAs),which boosted the power conversion efficiency to-20%[6,7].Along with the unprecedented success of organic solar cells,non-fullerene acceptors also find other optoelectronic applications.In particular,high-performance organic photodetectors(OPDs)[8,9]based on non-fullerene acceptors have been reported.
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 12074059, 11974152, and 11404055)Heilongjiang Postdoctoral Fund (Grant No. LBH-Q21061)。
文摘The selection of photoactive layer materials for organic solar cells(OSCs) is essential for the photoelectric conversion process.It is well known that chlorophyll is an abundant pigment in nature and is extremely valuable for photosynthesis.However,there is little research on how to improve the efficiency of chlorophyll-based OSCs by matching chlorophyll derivatives with excellent non-fullerene acceptors to form heterojunctions.Therefore in this study we utilize a chlorophyll derivative,Ce_(6)Me_(3),as a donor material and investigate the performance of its heterojunction with acceptor materials.Through density functional theory,the photoelectric performances of acceptors,i ncluding the fullerene derivative PC_(71)BM and the terminal halogenated non-fullerene DTBCIC series,are compared in detail.It is found that DTBCIC-C1 has better planarity,light absorption,electron affinity,charge reorganization energy and charge mobility than others.Ce_(6)Me_(3) has good energy level matching and absorption spectral complementarity with the investigated acceptor molecules and also shows good electron donor properties.Furthermore,the designed Ce_(6)Me_(3)/DTBCIC interfaces have improved charge separation and reorganization rates(K_(CS)/K_(CR)) compared with the Ce_(6)Me_(3)/PC_(71)BM interface.This research provides a theoretical basis for the design of photoactive layer materials for chlorophyll-based OSCs.
基金supported by the National Natural Science Foundation of China(21875286)the National Key Research and Development Program of China(2017YFA0206600)+1 种基金the Science Fund for Distinguished Young Scholars of Hunan Province(2017JJ1029)the Natural Sciences and Engineering Research Council of Canada。
文摘Since the world-record power conversion efficiency of 15.7%was achieved for organic solar cells(OSCs)in 2019,the newly developed non-fullerene acceptor(NFA)Y6 with an A-DA′D-A structure(A denotes an electron-accepting moiety,D denotes an electron-donating moiety)has attracted increasing attention.Subsequently,many new A-DA′D-A NFAs have been designed and synthesized,and the A-DA′D-A NFAs have played a significant role in the development of high-performance non-fullerene organic solar cells(NF-OSCs).Compared with the classical A-D-A-type acceptors,A-DA′D-A NFAs contain an electrondeficient core(such as benzothiadiazole(BT),benzotriazole(BTA),quinoxaline(Qx),or their derivatives)in the ladder-type fused rings to fine-tune the energy levels,broaden light absorption and achieve higher electron mobility of the NFAs.This review emphasizes the recent progress on these emerging A-DA′D-A(including Y-series)NFAs.The synthetic methods of DA′D-fused rings are introduced.The relationships between the chemical structure of the A-DA′D-A NFAs and the photovoltaic performance of the corresponding OSCs are summarized and discussed.Finally,issues and prospects for further improving photovoltaic performance of the OSCs are also proposed.
基金supported by the National Natural Science Foundation of China(91433202,52103202)National Key Research and Development Program of China(2019YFA0705900)funded by MOST+10 种基金the Basic and Applied Research Major Program of Guangdong Province(2019B030302007)the Shenzhen Science and Technology Innovation Commission(Shenzhen Fundamental Research Program,JCYJ20200109140801751)the Hong Kong Research Grants Council(RIF project R6021-18,CRF project C6023-19G,GRF project 16310019,16310020)Hong Kong Innovation and Technology Commission(ITCCNERC14SC01)and Foshan-HKUST(FSUST19-CAT0202)the support from Ministry of Science and Technology(2016YFA0200700)NSFC(21704082,21875182,21534003)Key Scientific and Technological Innovation Team Project of Shaanxi Province(2020TD-002)China Postdoctoral Science Foundation(2017M623162)111 project 2.0(BP2018008)the financial support from Research Grant Council of Hong Kong(14303519)CUHK Direct Grant(4053415)。
文摘Side-chain engineering has been demonstrated as an effective method for fine-tuning the optical,electrical,and morphological properties of organic semiconductors toward efficient organic solar cells(OSCs).In this work,three isomeric non-fullerene small molecule acceptors(SMAs),named as BTP-4F-T2C8,BTP-4F-T2EH and BTP-4F-T3EH,with linear and branched alkyl chains substituted on the α or β positions of thiophene as the side chains,were synthesized and systematically investigated.The results demonstrate that the size and substitution position of alkyl side chains can greatly affect the electronic properties,molecular packing as well as crystallinity of the SMAs.After blending with donor polymer D18-Cl,the prominent device performance of 18.25% was achieved by the BTP-4F-T3EH-based solar cells,which is higher than those of the BTP-4F-T2EH-based(17.41%)and BTP-4F-T2C8-based(15.92%)ones.The enhanced performance of the BTP-4F-T3EH-based devices is attributed to its stronger crystallinity,higher electron mobility,suppressed bimolecular recombination,and the appropriate intermolecular interaction with the donor polymer.This work reveals that the side chain isomerization strategy can be a practical way in tuning the molecular packing and blend morphology for improving the performance of organic solar cells.
基金the National Key R&D Program of"Strategic Advanced Electronic Materials"(No.2016YFB0401100)the National Natural Science Foundation of China(Grant No.61574077)+1 种基金Major Program of Natural Science Foundation of the Higher Education Institutions of Jiangsu Province,China(No.19KJA460005)Natural Science Foundation of Jiangsu Province(BK20170961).
文摘Recently,polymer solar cells developed very fast due to the application of non-fullerence acceptors.Substituting asymmetric small molecules for symmetric small molecule acceptors in the photoactive layer is a strategy to improve the performance of polymer solar cells.The asymmetric design of the molecule is very beneficial for exciton dissociation and charge transport and will also fine-tune the molecular energy level to adjust the open-circuit voltage(Voc)further.The influence on the absorption range and absorption intensity will cause the short-circuit current density(Jsc)to change,resulting in higher device performance.The effect on molecular aggregation and molecular stacking of asymmetric structures can directly change the microscopic morphology,phase separation size,and the active layer's crystallinity.Very recently,thanks to the ingenious design of active layer materials and the optimization of devices,asymmetric non-fullerene polymer solar cells(A-NF-PSCs)have achieved remarkable development.In this review,we have summarized the latest developments in asymmetric small molecule acceptors(A-NF-SMAs)with the acceptor-donor-acceptor(A-D-A)and/or acceptor-donor-acceptor-donor-acceptor(A-D-A-D-A)structures,and the advantages of asymmetric small molecules are explored from the aspects of charge transport,molecular energy level and active layer accumulation morphology.
基金This work was supported by the National Natural Science Foundation of China(51773046,51673048,21602040)the Strategic Priority Research Program of Chinese Academy of Sciences(XDB36000000)+1 种基金the Key Research Program of Frontier Sciences,Chinese Academy of Sciences(QYZDBSSW-SLH033)the National Key Research and Development Program of China(2017YFA0206600).
文摘For non-fullerene acceptors(NFAs)with linear A_(2)-A_(1)-D-A_(1)-A_(2) backbone,there are three kinds of possible intermolecular interaction,A_(1)-A_(1),A_(1)-A_(2) and A_(2)-A_(2) stacking.Hence,it is a huge challenge to control this interaction and investigate the effect of intermolecular stacking model on the photovoltaic performance.Here,we adopt a feasible strategy,by utilizing different substituent groups on terminal A2 unit of dicyanomethylene rhodanine(RCN),to modulate this stacking model.According to theoretical calculation results,the molecule BTA3 with ethyl substituent packs via heterogeneous interaction between A_(2) and A_(1) unit in neighboring molecules.Surprisingly,the benzyl group can effectively transform the aggregation of BTA5 into homogeneous packing of A_(2)-A_(2) model,which might be driven by the strong interaction between benzyl and A1(benzotriazole)unit.However,different with benzyl,phenyl end group impedes the intermolecular interaction of BTA4 due to the large steric hindrance.When using a BTA-based D-π-A polymer J52-F as donor according to“Same-A-Strategy”,BTA3-5 could achieve ultrahigh open-circuit voltage(VOC)of 1.17–1.21 V.Finally,BTA5 with benzyl groups realized an improved power conversion efficiency(PCE)of 11.27%,obviously higher than that of BTA3(PCE=9.04%)and BTA4(PCE=5.61%).It is also worth noting that the same trend can be found when using other four classic p-type polymers of P3HT,PTB7,PTB7-Th and PBDB-T.This work not only investigates the intermolecular interaction of A_(2)-A_(1)-D-A_(1)-A_(2) type NFAs for the first time,but also provides a straightforward and universal method to change the interaction model and improve the photovoltaic performance.
基金This work was supported by the Ministry of Science and Technology of China(2019YFA0705900)the National Natural Science Foundation of China(51773095,21935007,51873089)+2 种基金the Natural Science Foundation of Tianjin City(17JCJQJC44500)the Program of Introducing Talents of Discipline to Universities of China(111 Project)(B12015)The authors also thank the staff from Beijing Synchrotron Radiation Facility(BSRF)for the support of 2D-GIWAXS measurements.
文摘Side chain engineering plays a substantial role for high-performance organic solar cells (OSCs).Herein,a series of non-fullerene acceptor (NFA) molecules with A-D-A structures,TTCn-4F,with gradient substituent lengths of terminal side chains (T-SCs) on the molecular backbones have been designed and synthesized.The effects of T-SCs length,ranging from hydrogen atom to n-dodecyl,their optoelectronic properties,thin film molecular packing,blend film morphology,and overall photovoltaic performance have been systematically studied.The results show that among this series of molecules,TTC8-4F with n-octyl substituent,showed the best photovoltaic performance when applied with PM6 as the donor due to its favorable morphology,balanced charge mobility,effective exciton dissociation and less charge recombination.Based on this,its ternary device with F-Br as the secondary acceptor achieved a high PCE of 15.34%with the simultaneously enhanced Voc of 0.938 V,Jscof 22.66 mA cm^-2,and FF of 72.15%.These results indicate that the engineering of T-SCs is an effective strategy for designing high-performance NFAs.
基金financially supported by the National Natural Science Foundation of China (Nos. 21875216, 21734008)Zhejiang Province Science and Technology Plan (No. 2018C01047)the financial support from Research Grant Council of Hong Kong (General Research Fund No. 14314216, CUHK Direct Grant No. 4053227)
文摘To achieve the red-shifted absorptions and appropriate energy levels of A-D-A type non-fullerene acceptors(NFAs), in this work, we design and synthesize two new NFAs, named TPDCIC and TPDCNC, whose electron-donating(D) unit is constructed by a thieno[3,4-c]pyrrole-4,6-dione(TPD) core attached to two cyclopentadithiophene(CPDT) moieties at both sides, and the electronaccepting(A) end-groups are 2-(3-oxo-2,3-dihydroinden-1-ylidene)malononitrile(IC) and 2-(3-oxo-2,3-dihydro-1 H-cyclopenta[b]naphthalen-1-ylidene)malononitrile(NC), respectively. Benefiting from TPD core, which easily forms quinoid structure and O···H or O···S intramolecular noncovalent interactions, TPDCIC and TPDCNC show more delocalization of π-electrons and perfect planar molecular geometries, giving the absorption ranges extended to 822 and 852 nm, respectively. Furthermore, the highest occupied molecular orbital(HOMO) levels of TPDCIC and TPDCNC remain relatively low-lying due to the electronegativity of the carbonyl groups on TPD core. Considering that the absorptions and energy levels of the two NFAs match well with those of a widely used polymer donor, PBDB-T, we fabricate two kinds of organic solar cells(OSCs) based on the PBDB-T:TPDCIC and PBDB-T:TPDCNC blended films, respectively. Through a series of optimizations, the TPDCIC-based devices yield an impressing power conversion efficiency(PCE)of 10.12% with a large short-circuit current density(JSC) of 18.16 mA·cm-2, and the TPDCNC-based ones exhibit a comparable PCE of9.80% with a JSC of 17.40 mA·cm-2. Our work is the first report of the TPD-core-based A-D-A type NFAs, providing a good reference for the molecular design of high-performance NFAs.
基金supported by the National Science Foundation of China (NSFC, Nos. 51573107, 91633301 and 21432005)the Foundation of State Key Laboratory of Polymer Materials Engineering (No. sklpme 2017-2-04)
文摘Recently, perylene diimide (PDI) derivatives were attractive as the electron-deficient acceptor materials in non-fullerene organic solar cells since Tang first used a single PDI compound as the n-type semiconductor to fabricate photovoltaic devices in 1986, which achieved a power conversion efficiency of 1%. Beside the monomeric PDIs, the linear and three dimensional (3D) PDl-based small molecular acceptors have also made great achievements with the power conversion efficiencies over 9.0% in single- junction polymer solar cells, and over 10.0% in tandem solar cells. The excellent device performance can be realized by forming suitable twisted structure, developing suitable donor materials and optimizing device technologies. In this review, we summarize the recent development of PDl-based small molecular non-fullerene acceptors in non-fullerene organic solar cells, including molecular design strategies and structure-property relationships.
基金the financial support by the National Natural Science Foundation of China(51303099)the Natural Science Basic Research Plan in Shaanxi Province of China(2017JM5058)the Funded Projects for the Academic Leaders and Academic Backbones,Shaanxi Normal University(16QNGG008)
文摘Fullerenes and their derivatives are important types of electron acceptor materials and play a vital role in organic solar cell devices. However, the fullerene acceptor material has some difficulties to overcome the intrinsic shortcomings, such as weak absorption in the visible range, difficulty in modification and high cost, which limit the performance of the device and the large-scale application of this type of acceptors. In recent years, non-fullerene electron acceptor material has attracted the attention of scientists due to the advantages of adjustable energy level, wide absorption, simple synthesis, low processing cost and good solubility. Researchers can use the rich chemical means to design and synthesize organic small molecules and their oligomers with specific aggregation morphology and excellent optoelectronic prop- erties. Great advances in the field of synthesis, device engineering, and device physics of non-fullerene acceptors have been achieved in the last few years. At present, non-fullerene small molecules based photovoltaic devices achieve the highest efficiency more than 13% and the efficiency gap between fullerenetype and non-fullerene-type photovoltaic devices is gradually narrowing. In this review, we explore recent progress of non-fullerene small molecule electron acceptors that have been developed and led to highefficiency photovoltaic devices and put forward the prospect of development in the future.
基金The authors ack no wledge the fin ancial support from the Ministry of Science and Technology of China(No.2016YFA0200700)the National Natural Science Foundation of China(Nos.21822503,51973043,21534003,21721002)+1 种基金the Beijing Nova Program(No.Z17110001117062)Youth Innovation Promotion Association,K.C.Wong Education Foundation,and the Chinese Academy of Scien ces.
文摘Summary of main observation and conclusion The ternary blend structure has been demonstrated as an effective approach to increase the power conversion efficiency of organic solar cells.An effective approach to enhance the power conversion efficiency of ternary solar cells is based on two non-fullerene acceptors with complimentary absorption range and balanced crystallinity.In this work,we have introduced a high crystallinity small-molecule acceptor,named C8IDTT-4CI with appropriate alkyl side chains into a low crystalline blend of conjugated polymer donor PBDT-TPD and fused-ring electron acceptor ITIC-4F.A ternary device based on the blend PBDT-TPD:1TIC-4F:C81DTT-4CI exhibits a best power conversion efficiency of 9.51%with a simultaneous improvement of the short-circuit current density to 18.76 mA-cm^-2 and the fill factor up to 67.53%.The absorption onset for C8IDTT-4CI is located at 900 nm,so that the well complementary light absorption is beneficial to the photocurrent.In addition,the existence of high crystallinity C8IDTT-4CI in the ternary device is found helpful to modulate crystallinity,improve heterojunction morphologies and stacking structure,therefore to realize higher charge mobility and better performance.
基金financially supported by the National Key Research and Development Program of China (No. 2019YFA0705900) funded by MOSTthe Basic and Applied Basic Research Major Program of Guangdong Province (No. 2019B030302007)the National Natural Science Foundation of China (No. 51521002)。
文摘Non-fullerene polymer solar cells(NF-PSCs) have gained wide attention recently. Molecular design of non-fullerene electron acceptors effectively promotes the photovoltaic performance of NF-PSCs. However,molecular electron acceptors with 2-dimensional(2 D) configuration and conjugation are seldom reported.Herein, we designed and synthesized a series of novel 2 D electron acceptors for efficient NF-PSCs. With rational optimization on the conjugated moieties in both vertical and horizontal direction, these 2 D electron acceptors showed appealing properties, such as good planarity, full-spectrum absorption, high absorption extinction coefficient, and proper blend morphology with donor polymer. A high PCE of 9.76%was achieved for photovoltaic devices with PBDB-T as the donor and these 2 D electron acceptors. It was also found the charge transfer between the conjugated moieties in two directions of these 2 D molecules contributes to the utilization of absorbed photos, resulting in an exceptional EQE of 87% at 730 nm. This work presents rational design guidelines of 2 D electron acceptors, which showed great promise to achieve high-performance non-fullerene polymer solar cells.
基金supported by the National Key Re search and Development Program of China(2019YFA0705900)funded by MOSTthe Basic and Applied Basic Research Major Program o Guangdong Province(2019B030302007)。
文摘Side-chain engineering has been considered as one of the most promising strategies to optimize non-fullerene small-molecule acceptors(NFSMAs).Previous efforts were focused on the optimization of alkyl-chain length,shape,and branching sites.In this work,we propose that asymmetric side-chain engineering can effectively tune the properties of NFSMAs and improve the power conversion efficiency(PCE)for binary non-fullerene polymer solar cells(NFPSCs).Specifically,by introducing asymmetric side chains into the central core,both of the absorption spectra and molecule orientation of NFSMAs are efficiently tuned.When blended with polymer donor PM6,NFPSCs with EH-HD-4F(2-ethylhexyl and 2-hexyldecyl side chains)demonstrate a champion PCE of 18.38%with a short-circuit current density(J_(SC))of 27.48 mA cm^(-2),an open circuit voltage(V_(OC))of 0.84 V,and a fill factor(FF)of 0.79.Further studies manifest that the proper asymmetric side chains in NFSMAs could induce more favorable face-on molecule orientation,enhance carrier mobilities,balance charge transport,and reduce recombination losses.
基金financially supported by NSFC(Nos.21190032,21372226)the Strategic Priority Research Program of the Chinese Academy of Sciences(No.XDA09020000)
文摘Non-fullerene organic solar cells have received increasing attentions in these years,and great progresses have been made since 2013.Among them,aromatic di-amide/imide-containing frameworks have shown promising applications.The outstanding properties of them are highly associated with their unique electronic and structural features,such as strong electron-withdrawing nature,broad absorption in UVvisible region,tunable HOMO/LUMO energy levels,easy modifications,and excellent chemical,thermal and photochemical stabilities.In this review,we give an overview of recent developments of aromatic diamide/imide-containing small molecules used as electron acceptors for organic solar cells.
基金Funded by the National Natural Science Foundation of China(No.21673170)
文摘Two novel non-fullerene small molecule acceptors were prepared with the conjugated backbone of 5 H-fluoreno[3, 2-b:6, 7-b’] dithiophene carrying the electron deficient unit of dicyanomethylene indanone(DICTFDT) and rhodanine(TFDTBR), respectively. The two acceptors exhibited excellent thermal stability and strong absorption in the visible region. The LUMO level is estimated to be at-3.89 eV for DICTFDT and-3.77 eV for TFDTBR. When utilized as the acceptor in bulk heterojunction polymer solar cells with the polymer donor of PBT7-Th, the optimized maximum power conversion efficiency of 5.12% and 3.95% was obtained for the device with DICTFDT and TFDTBR, respectively. The research demonstrates that 5 H-fluoreno[3, 2-b:6, 7-b’] dithiophene can be an appealing candidate for constructing small molecular electron acceptor towards efficient polymer:non-fullerene bulk heterojunction solar cells.
基金supported by the Ministry of Science and Technology(2014CB643501)the National Natural Science Foundation of China(21520102006,21634004,21490573)the Guangdong Natural Science Foundation(S2012030006232)
文摘A series of novel wide bandgap small molecules(IFT-ECA, IFT-M, IFT-TH and IFT-IC) based on the A-D-A structure with indenofluorene core, thiophene bridge, and different electron-deficient end-capping groups, were synthesized and used as non-fullerene acceptors in organic solar cells. The influences of end-capping groups on the device performance were studied.The four materials exhibited different physical and chemical properties due to the variation of end-capping groups, which further affect the exciton dissociation, charge transport, morphology of the bulk-heterojunction films and device performance. Among them, IFT-IC-based device delivered the best power conversion efficiency of 7.16% due to proper nano-scale phase separation morphology and high electron mobility, while the devices based on the other acceptors achieved lower device performance(4.14% for IFT-TH, <1% for IFT-ECA and IFT-M). Our results indicate the importance of choosing suitable electron-withdrawing groups to construct high-performance non-fullerene acceptors based on A-D-A motif.