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%.

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.

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.

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.

基于非富勒烯小分子受体Y6的有机太阳能电池

随着给/受体材料的不断发展,有机太阳能电池的器件效率不断取得进展。特别是非富勒受体分子Y6的出现,使单结有机太阳能电池的效率突破了15%。Y6已经应用到了有机太阳能电池各个方面并且极大提升了其性能。本综述主要总结了Y6在二元、三元和四元、逐层印刷、柔性、叠层和半透明等有机太阳能电池方面的研究情况,以及基于Y6三线态的有机太阳能电池的进展,最后对Y6的结构优化及在器件领域中的应用进行了展望。

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.

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.

Recent progress in organic solar cells(PartⅡdevice engineering)

1 Introduction Organic solar cells(OSCs)belong to a multidisciplinary field composed of chemistry,materials science,physics,engineering,etc.For a better reviewing of this field,we briefly divide the research field of OSCs into two parts:material science and device engineering.In our previous review,the material science part of OSCs,including conjugated polymer donors and acceptors,small molecular donors and acceptors.

Understanding energetic disorder in electron-deficient-core-based non-fullerene solar cells

Recent advances in material design for organic solar cells(OSCs)are primarily focused on developing near-infrared nonfullerene acceptors,typically A-DA′D-A type acceptors(where A abbreviates an electron-withdrawing moiety and D,an electron-donor moiety),to achieve high external quantum efficiency while maintaining low voltage loss.However,the charge transport is still constrained by unfavorable molecular conformations,resulting in high energetic disorder and limiting the device performance.Here,a facile design strategy is reported by introducing the"wing"(alkyl chains)at the terminal of the DA′D central core of the A-DA′D-A type acceptor to achieve a favorable and ordered molecular orientation and therefore facilitate charge carrier transport.Benefitting from the reduced disorder,the electron mobilities could be significantly enhanced for the"wing"-containing molecules.By carefully changing the length of alkyl chains,the mobility of acceptor has been tuned to match with that of donor,leading to a minimized charge imbalance factor and a high fill factor(FF).We further provide useful design strategies for highly efficient OSCs with high FF.

Manipulating molecular aggregation and crystalline behavior of A-DA’D-A type acceptors by side chain engineering in organic solar cells

Alkyl chains engineering plays an important role in photovoltaic materials for organic solar cells.Herein,three A-DA’D-A(acceptor–donor–acceptor’–donor–acceptor)type acceptors named Y6,Y6-C4,and Y6-C5 with different branching position on the pyrrole motif are discussed and the relationship between molecular aggregation,crystalline,and device performance are systematically investigated.The distance between the branching position and the main backbone affects their optical absorption and energy levels.Y6-C4 and Y6-C5 with the branching position at the fourth and fifth carbon of the alkyl chain show blue-shifted absorption and increased electrochemical bandgaps,compared with Y6 with the branching position at the second carbon of the alkyl side chain.In addition,this distance influences the molecular aggregation and crystalline behavior of the donor/acceptor blends.Compared with Y6-C4,Y6-C5 possesses a stronger crystalline and aggregate ability in the blends with a lower non-radiative energy loss,which results in a higher open circuit voltage(Voc)of 0.88 V.Finally,Y6-C5-based binary device achieved a high power conversion efficiency up to 16.73%with afill factor(FF)of 0.78.These results demonstrate that the side chain engineering is an effective strategy for tuning the molecular aggregation and crystalline to improve photovoltaic performance of the A-DA’D-A type acceptors.

Novel photoelectrochemical immunosensor for MCF-7 cell detection based on n-p organic semiconductor heterojunction

In this work,we developed a novel photoelectrochemical(PEC)sensor based on n-p organic semiconductor heterojunction for sensitive detecting MCF-7 cancer cells.BTA-C4 Ph and PM6 were designed as photoactive materials to form n-p heterojunction,which greatly enhanced the photoelectric conversion efficiency.Antibody-modified magnetic nanoparticles were utilized to capture and separate MCF-7 cells from samples.Detection of MCF-7 is ascribed to the loading of MCF-7 onto BTA-C4 Ph-PM6 modified electrode that resulted in the decrease of photocurrent intensity.The PEC immunosensor displayed a linear concentration ranging from 50 cell/m L to 1×10^(4) cell/m L with a limit of detection(LOD)of 41 cell/m L(S/N=3)for MCF-7.Additionally,the senor also exhibited good stability,excellent selectivity and prominent reproducibility.Furthermore,the sensor was successfully applied to detect MCF-7 in whole blood.This work illustrates that n-p heterojunction of organic semiconductor may find wide applications for the preparation of different photoelectrochemical sensors.

A-π-A structured non-fullerene acceptors for stable organic solar cells with efficiency over 17%

With the development of photovoltaic materials, especially the small molecule acceptors(SMAs), organic solar cells(OSCs)have made breakthroughs in power conversion efficiencies(PCEs). However, the stability of high-performance OSCs remains a critical challenge for future technological applications. To tackle the inherent instability of SMA materials under the ambient conditions, much effort has been made to improve OSCs stability, including device modification and new materials design. Here we proposed a new electron acceptor design strategy and developed a “quasi-macromolecule”(QM) with an A-π-A structure,where the functionalized π-bridge is used as a linker between two SMAs(A), to improve the long-term stability without deteriorating device efficiencies. Such type of QMs enables excellent synthetic flexibility to modulate their optical/electrochemical properties, crystallization and aggregation behaviors by changing the A and π units. Moreover, QMs possess a unique long conjugated backbone combining high molecular weight over 3.5 k Da with high purity. Compared with the corresponding SMA BTP-4F-OD(Y6-OD), the devices based on newly synthesized A-π-A type acceptors QM1 and QM2 could exhibit better device stability and more promising PCEs of 17.05% and 16.36%, respectively. This kind of “molecular-framework”(A-π-A)structure provides a new design strategy for developing high-efficiency and-stability photovoltaic materials.