Alkyl chain modulation of asymmetric hexacyclic fused acceptor synergistically with wide bandgap third component for high efficiency ternary organic solar cells

Herein,two asymmetric hexacyclic fused small molecule acceptors(SMAs),namely BP4F-HU and BP4F-UU,were synthesized.The elongated outside chains in the BP4F-UU molecule played a crucial role in optimizing the morphology of blend film,thereby improving charge mobility and reducing energy loss within the corresponding film.Notably,the PM6:BP4F-UU device exhibited a higher open-circuit voltage(V_(oc))of 0.878 V compared to the PM6:BP4F-HU device with a V_(oc)of 0.863 V.Further,a new wide bandgap SMA named BTP-TA was designed and synthesized as the third component to the PM6:BP4F-UU host binary devices,which showed an ideal complementary absorption spectrum in PM6:BP4F-UU system.In addition,BTP-TA can achieve efficient intermolecular energy transfer to BP4F-UU by fluorescence resonance energy transfer(FRET)pathway,due to the good overlap between the photoluminescence(PL)spectrum of BTP-TA and the absorption region of BP4F-UU.Consequently,ternary devices with 15wt%BTP-TA exhibits broader photon utilization,optimal blend morphology,and reduced charge recombination compared to the corresponding binary devices.Consequently,PM6:BP4F-UU:BTP-TA ternary device achieved an optimal power conversion efficiency(PCE)of 17.83%with simultaneously increased V_(oc)of 0.905 V,short-circuit current density(J_(sc))of 26.14 mA/cm^(2),and fill factor(FF)of 75.38%.

Predicting power conversion efficiency of binary organic solar cells based on Y6 acceptor by machine learning

Organic solar cells(OSCs)are a promising photovoltaic technology for practical applications.However,the design and synthesis of donor materials molecules based on traditional experimental trial-anderror methods are often complex and expensive in terms of money and time.Machine learning(ML)can effectively learn from data sets and build reliable models to predict the performance of materials with reasonable accuracy.Y6 has become the landmark high-performance OSC acceptor material.We collected the power conversion efficiency(PCE)of small molecular donors and polymer donors based on the Y6 acceptor and calculated their molecule structure descriptors.Then we used six types of algorithms to develop models and compare the predictive performance with the coefficient of determination(R^(2))and Pearson correlation coefficient(r)as the metrics.Among them,decision tree-based algorithms showed excellent predictive capability,especially the Gradient Boosting Regression Tree(GBRT)models based on small molecular donors and polymer donors exhibited that the values of R2are 0.84 and 0.69 for the testing set,respectively.Our work provides a strategy to predict PCEs rapidly,and discovers the influence of the descriptors,thereby being expected to screen high-performance donor material molecules.

有机化学实验操作失误引导创新——以正溴丁烷制备为例

用正丁醇、溴化钠和硫酸反应制备正溴丁烷是基础有机化学实验教学经常选用的实验,本文设计了以正丁醇、溴化钠和硫酸为原料,使用尾气吸收回流加热装置,先将其中任意两个加热至回流,再瞬间加入第三个原料,详细考察了不同原料加入顺序、不同回流反应时间对正溴丁烷的产率的影响。实验结果可为国内院校开设有机化学实验课程提供实践参考,并启发学生从实验失误中也可以引导实验创新。

苯甲酸、对甲苯胺、乙酰苯胺三组分分离实验教学设计

分离提纯是有机合成中关键的实验步骤,反应后处理这部分的工作内容要占到90%的工作量。为提高学生从混合物中分离目标化合物的实验技能,进一步锻炼学生综合运用萃取、蒸馏、重结晶等纯化实验操作,中南大学化学化工学院有机化学教学组在有机化学实验教学中安排了"三组分混合物分离"实验,面向的学生为医学临床五年制和八年制、化学化工学院的制药工程及应用化学专业。本文详细探讨了该实验的酸、碱分离两种教学方案,对先加酸分离得到的三个组分进行了1H NMR测试。从两个方案的实验教学效果来看,先加酸或先加碱对实验结果没有影响。

苯甲酸、对氨基苯甲酸乙酯、乙酰苯胺三组分分离实验教学设计

为锻炼学生综合运用萃取、蒸馏、重结晶等纯化实验操作,提高学生从混合物中分离并提纯目标化合物的实验技能,中南大学化学化工学院有机化学教学组在有机化学实验教学中安排了“三组分混合物的分离”实验,面向临床医学(五年制、八年制)、药学、生物科学等专业,以及化学化工学院所有专业。鉴于对甲苯胺有毒性,给做实验的学生、实验室教师和指导教师身体带来较大危害,产生的废水对环境也有相当的危害。同时,由于其熔点低,实验室教师每次都要准备冰块,不利于节能省电。尝试使用绿色无毒、熔点较高的对氨基苯甲酸乙酯替代对甲苯胺,可以很好地避免上述两个问题,我们在实验室反复多次做了先加酸或先加碱的两种分离方案后,在有机化学实验B的教学中进行了初步推广,取得了良好的教学效果。

A new non-fullerene acceptor based on the heptacyclic benzotriazole unit for efficient organic solar cells

Non-fullerene acceptors(NFAs)become an interesting family of organic photovoltaic materials,and have attracted considerable interest for their great potential in manufacturing large-area flexible solar panels by low cost coating methods[1–5].Recently,our group proposed in the first time an A-DA’D-A molecular strategy and synthesized a new class of non-fullerene acceptor Y6 with a record efficiency above 15%with single junction organic solar cells(OSCs)[6].To further improve the photovoltaic performance of OSCs,many effective strategies have been successfully explored,such as side-chain engineering and extension of fused core and terminal group engineering[7–12].As well-known,PCE of devices is determined by the open circuit voltage(Voc),short-circuit current density(Jsc)and fill factor(FF)[13].Among them,Voc is associated with low-lying highest occupied molecular orbital(HOMO)of donor and lowest unoccupied molecular orbital(LUMO)of acceptor of the active layer[14–16].Side-chain engineering is an effective strategy for manipulating energy levels and improving photovoltaic performance of devices[17–19].For example,introducing the alkyl/alkoxy chains can effectively tune the HOMO/LUMO energy levels[20–22].Tang et al.have reported a novel non-fullerene acceptor ITC6-IC.ITC6-IC has relatively high LUMO level and high Voc than those of ITIC due to the introduction of weak electrondonating hexyl group on thiophene[23].

26.75 cm^(2) organic solar modules demonstrate a certified efficiency of 14.34%

Organic solar cells(OSCs)have been developed rapidly in past years,due to the fast evolution of wide-bandgap copoly-mer donors and low-bandgap non-fullerene acceptors[1−9].At present,the highest power conversion efficiencies(PCEs)for single-junction OSCs and tandem OSCs exceed 19%and 20%,respectively[10,11].These OSCs are typically fabricated by us-ing low-boiling-point solvent chloroform(CF)with an effect-ive area<0.1 cm^(2).The doctor-blading deposition is the most advantageous technique to fabricate OSCs with low-boiling-point solvent for upscaling lab cells to industrial-scale mod-ules[12],exhibiting simple operation,low cost,and high materi-al utilization[13−15].Herein,a typical OSC material system PM6:Y6(Fig.1(a))was used to fabricate OSCs modules via doc-tor-blading deposition in ambient condition,and the influ-ence of the ambient temperature and substrate temperature on the film quality was investigated.

Optimizing side chains on different nitrogen aromatic rings achieving 17% efficiency for organic photovoltaics

Balancing charge generation and low energy loss(E_(loss)), especially in the wide spectral absorption region is critical to obtain high-performance organic photovoltaics(OPVs). Therefore, Y11-M and Y11-EB are designed and synthesized through modifying alkyl chains on different nitrogen aromatic rings of the reported non-fullerene acceptor Y11. Although all the molecules have almost similar low band-gap(around 1.30 e V), Y11-M and Y11-EB exhibit wider absorption in 410–870 nm region. Eventually, the conventional devices based on Y11-M and Y11-EB possess more efficient charge generation with low Eloss(around 0.44 e V). In addition, outstanding efficiencies of 16.64% and 17.15% with the fill factor of 76.15% and 74.73% are obtained in PM6:Y11-M and PM6:Y11-EB-based devices, both higher than Y11:PM6. The results highlight the importance of rational alkyl chains optimization, and a good structureproperty relationship is established as well.

Diflurobenzothiadiazole core-based noncovalently fused small molecule acceptor exhibiting over 12% efficiency and high fill factor

The versatility and flexibility of organic photoelectric materials endow organic photovoltaic cells fine function modulation and huge commercial potential. In this work, a new noncovalent fused-ring small molecule acceptor(SMA) BID-4 F has been synthesized for high-efficient organic solar cells(OSCs). BID-4 F consists of a diflurobenzothiadiazole(DFBT) core, ladder-like indacenodithiophene(IDT) spacers, and dicyanoindanone electron-withdrawing end groups, which are supposed to be conformationally interlocked by noncovalent interactions, leading to good molecular planarity. In addition, compact solid state stacking was revealed by UV–vis–NIR absorption spectrum. The optimized PM6:BID-4 F based device delivers an eminent power conversion efficiency(PCE) of 12.30% with a high open-circuit voltage(Voc) of 0.92 V and a high fill factor(FF) of 74.3%. Most importantly, the PCE and FF are among one of the highest values reported for the OSCs based on the unfused-ring SMAs. Overall, our work demonstrates that the unfused ring central framework with high molecular planarity through noncovalent interactions provides a good strategy to construct highly efficient SMAs.

Synergistic adsorption and catalytic effects of Ti_(3)C_(2)T_(x)/CoO/MoO_(3) composite on lithium polysulfides for high-performance lithium–sulfur batteries

The shuttle effect of lithium polysulfides(LiPSs)and their sluggish kinetic processes lead to rapid capacity fading and poor cycling stability in lithium-sulfur(Li-S)batteries,limiting their commercial viability.This study proposes a functionalized separator with adsorption and synergistic catalysis ability for Li-S batteries.The modified separator comprises Ti_(3)C_(2)T_(x) sheets,CoO,and MoO_(3).Experimental and theoretical calculations demonstrate that Ti_(3)C_(2)T_(x)/CoO/MoO_(3) composite not only effectively inhibits the shuttle effect of LiPSs,ensuring efficient utilization of active materials,but also enhances reversibility and reaction kinetics among LiPSs.The full exposure of active sites in the Ti_(3)C_(2)T_(x)/CoO/MoO_(3) composite and the synergistic action of different catalysts enable efficient capture and conversion of LiPSs molecules at the material surface.Besides,the lithium-sulfur batteries with Ti_(3)C_(2)T_(x)/CoO/MoO_(3)@PP separator exhibited only a 0.042%capacity decay per cycle at 0.5 C(800 cycles).Moreover,a high areal capacity of 6.85 mAh cm-2 was achieved at high sulfur loading(7.9 mg cm-2)and low electrolyte-to-sulfur ratio(10μL mg-1).

原子级化学反应促进可弱光探测有机光电倍增探测器的外量子效率超过10^(8)%

外量子效率远大于100%、低成本、溶液法制备的倍增型有机光电探测器(PM-OPDs)引起广泛关注.但该类器件因阳极欧姆接触带来暗电流的恶化,使其弱光探测并不理想.基于此,本文提出了原子级化学反应改善PM-OPDs暗电流及弱光探测策略,进而带来器件综合性能的显著提升.具体地,本文利用原子层沉积技术在空穴传输层PEDOT:PSS与活性层P3HT:PC71BM(100:1)之间引入0.8 nm厚的Al_(2)O_(3)界面层,通过对薄膜拉曼、XPS及FT-IR性能进行表征,发现原子级厚度的Al_(2)O_(3)可与PEDOT:PSS的化学基团发生反应,调节PEDOT:PSS的功函数,进而在阳极一侧形成肖特基接触.通过与阴极肖特基接触协同,器件在保持高倍增行为的同时,暗电流显著降低.最终,器件的弱光探测性能有所改善,相比于标准器件(可探测64 nW/cm^(2)弱光),Al_(2)O_(3)修饰器件可探测低至2.5 nW/cm^(2)的弱光,且相应的外量子效率和响应率分别达到4.31×10^(8)%,1.85×10^(6)A/W,达到目前报道PM-OPDs的最优值.此策略在新型柔性电子产品及医学成像领域具有很好的应用前景.

Synergetic Alkoxy Side-Chain and Chlorine-Contained End Group Strategy toward High Performance Ultra-Narrow Bandgap Small Molecule Acceptors

Ultra-narrow bandgap(ultra-NBG)small molecule acceptors(SMAs)show great potential in organic solar cells(OSCs)due to the extended near-infrared(NIR)absorption.In this work,a synergetic alkoxy side-chain and chlorine-contained end group strategy is employed to achieve A-DA'D-A type ultra-NBG SMAs by introducing alkoxy chains with oxygen atom at the second position into the thiopheneβposition as well as replacing the F atoms with Cl atoms in the end group.As a result,the heptacyclic BZO-4F shows a redshifted absorption onset(960 nm)compared with Y11(932 nm)without oxygen atoms in the side chains.Then,the fluorinated end groups are substituted with the chlorinated ones to synthesize BZO-4Cl.The absorption onset of BZO-4Cl is further redshifted to 990 nm,corresponding to an optical ultra-NBG of 1.25 eV.When blending with the polymer donor PBDB-T,the binary devices based on PBDB-T:BZO-4F and PBDB-T:BZO-4Cl deliver power conversion efficiencies(PCEs)over 12%.Furthermore,ternary devices with the addition of BZ4F-O-1 into PBDB-T:BZO-4Cl system achieve the optimal PCE of 15.51%.This work proposes a synergetic alkoxy side-chain and chlorine-contained end group strategy to achieve A-DA'D-A type ultra-NBG SMAs,which is important for future molecular design.

All-in-one phototheranostics based on BTP-4F-DMO nanoparticles for NIR-II fluorescence/photoacoustic dual-mode imaging and combinational therapy

Various phototheranostics have recently been developed for phototherapy.Through proper molecular design,the photochemical and photophysical properties of these phototheranostics can be promoted.Herein,an acceptor-donor-acceptor(A-D-A)-structured dye,BTP-4F-DMO,was synthesized and prepared into water-soluble nanoparticles(NPs).The obtained BTP-4F-DMO NPs had strong absorption from650 nm to 850 nm and a fluorescence emission peak at~900 nm that tailed to~1100 nm.The NPs showed a superhigh photothermal conversion efficiency of 90.5%±5%and could simultaneously generate·OH and^(1)O_(2)with a^(1)O_(2)generation quantum yield of 4.6%under 808 nm laser irradiation.Due to these advanced properties,BTP-4F-DMO NPs can switch the role of autophagy from pro-survival to prodeath,thereby further promoting cancer cell death.These features make BTP-4F-DMO NPs a promising multifunctional phototheranostic agent for NIR-II fluorescence/photoacoustic dual-mode imaging-guided synergetic photodynamic/photothermal therapy.In general,this work provides a strategy for expanding the biomedical applications of organic A-D-A-structured phototheranostics.

A-DA’D-A Type Pentacyclic Small Molecule Acceptors to Exceed 16.5%Efficiency by Heteroatom Effect at the Outer Side Chain

Comprehensive Summary In this work,we adopt a“heteroatom side-chains”modification strategy to modify the thiophene units in A-DA'D-A(acceptor-donor-acceptor’-donor-acceptor)type pentacyclic SMAs(small molecule acceptors),that is,introducing branched alkyl chain at theβ-position of thiophene instead of straight alkyl chain,and then introducing oxygen atom at the third-position on the basis of branched chain.Two new pentacyclic SMAs(BZ4F-EH and BZ4F-OEH)were synthesized,and the influence of the heteroatom side-chains on photoelectric properties of A-DA'D-A type pentacyclic SMAs was systematically studied.Compared with our previously reported BZ4F(Y26),BZ4F-EH shows slightly blue-shifted absorption,while BZ4F-OEH has obvious red-shifted absorption.As a result,BZ4F-OEH-based binary device achieved a high power conversion efficiency(PCE)of 16.56%with a fill factor(FF)of 79.3%,which is the highest efficiency of pentacyclic SMAs to date.

Alkyl side chain engineering enables high performance as-cast organic solar cells of over 17%efficiency

Achieving high-performance as-cast OSCs is crucial for industrialization in the future,owing to the advantages of better stability,environmental-friendly,and decreasing production cost.In this regard,we synthesized an ADA′D-A type acceptor,Y6-eC6-BO,by shortening the straight alkyl side-chains on the thiophene position from C_(11) to C_(6) as well as lengthening the branched alkyl side-chains on the pyrrole position of Y6 to achieve a stronger crystallization and better miscibility than Y6.As a result,the corresponding chloroform-processed as-cast PM6:Y6-eC6-BO OSC showed a high PCE of 17.33%,which was one of the highest efficiencies of as-cast OSCs.And the as-cast PM6:Y6-eC6-BO OSCs processed from o-xylene displayed a PCE of 16.38%,as far as we know,this is among the highest efficiencies of non-halogenated-solvent processed as-cast OSCs.These results demonstrated tailoring the alkyl side-chain of NFAs is a feasible and simple approach to achieve high performance as-cast OSCs and provides guideline in molecular design in the future.

Recent progress in organic solar cells(PartⅠmaterial science)

During past several years,the photovoltaic performances of organic solar cells(OSCs)have achieved rapid progress with power conversion efficiencies(PCEs)over 18%,demonstrating a great practical application prospect.The development of material science including conjugated polymer donors,oligomer-like organic molecule donors,fused and nonfused ring acceptors,polymer acceptors,single-component organic solar cells and water/alcohol soluble interface materials are the key research topics in OSC field.Herein,the recent progress of these aspects is systematically summarized.Meanwhile,the current problems and future development are also discussed.

A-DA′D-A non-fullerene acceptors for high-performance organic solar cells

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.

5H-dithieno[3,2-b:20,30-d]pyran-5-one unit yields efficient wide-bandgap polymer donors

Recently,great progress has been made in organic solar cells due to the emergence of high-performance nonfullerene acceptors[1-6].Over 16%and 17%power conversion efficiencies(PCEs)were achieved for nonfullerene-acceptor-based single-junction and tandem cells,respectively[7,8].Owing to complementary light absorption,wide-bandgap donor-acceptor(D-A)copolymers are ideal electron-donating partners for nonfullerene acceptors.However,efficient D-A copolymer donors are still limited.

A chlorinated non-fullerene acceptor for efficient polymer solar cells

Improving the performance and reducing the manufacturing costs are the main directions for the development of organic solar cells in the future.Here,the strategy that uses chemical structure modification to optimize the photoelectric properties is reported.A new narrow bandgap(1.30 eV)chlorinated non-fullerene electron acceptor(Y15),based on benzo[d][1,2,3] triazole with two 3-undecylthieno[2’,3’:4,5] thieno[3,2-b] pyrrole fused-7-heterocyclic ring,with absorption edge extending to the near-infrared(NIR) region,namely A-DA’D-A type structure,is designed and synthesized.Its electrochemical and optoelectronic properties are systematically investigated.Benefitting from its NIR light harvesting,the fabricated photovoltaic devices based on Y15 deliver a high power conversion efficiency(PCE) of 14.13%,when blending with a wide bandgap polymer donor PM6.Our results show that the A-DA’D-A type molecular design and application of near-infrared electron acceptors have the potential to further improve the PCE of polymer solar cells(PSCs).

High efficiency ternary organic solar cells enabled by compatible dual-donor strategy with planar conjugated structures

Ternary organic solar cells(OSCs) have received extensive attention for improving the power conversion efficiency(PCE) of organic photovoltaics(OPVs). In this work, a novel donor material(ECTBD) consisting of benzodithiophene(BDT) central electron donor unit was developed and synthesized. The small molecular donor has the same central unit as PM6. The addition of ECTBD into PM6:Y6 system could improve the morphology of active blend layer. In addition, ECTBD showed good morphologically compatibility when blending with PM6:Y6 host, resulting in the improvement of fill factor and current density. As a result, the ternary devices based on PM6:ECTBD:Y6 ternary system achieved a highest PCE of 16.51% with fill factor of 76.24%, which was much higher than that of the binary devices(15.7%). Overall, this work provided an effective strategy to fabricate highly efficient ternary organic solar cells through design of the novel small molecular donor as the third component.