Control over π-π stacking of heteroheptacene-based nonfullerene acceptors for 16% efficiency polymer solar cells

Ma, Yunlong; Cai, Dongdong; Wan, Shuo; Yin, Pan; Wang, Pengsong; Lin, Wenyuan; Zheng, Qingdong

doi:10.1093/nsr/nwaa189

Cited by 96 publications

(89 citation statements)

References 54 publications

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“…Strong (100) diffraction peaks in the in-plane (IP) direction and (010) diffraction peaks in the out-of-plane (OOP) direction are identified from the GIWAXS patterns of the neat BTh-Th-2F and 2BTh-2F films, indicating the formation of face-on orientation with short π-π stacking distance of 3.60 Å (1.74 Å −1 ) and 3.55 Å (1.77 Å −1 ), respectively; whereas the molecular orientation is random in the neat 2Th-2F film. According to the Scherrer equation, i.e., CCL = 2π × 0.89/FWHM, [48,49] the crystal coherence length (CCL) is derived to analyze the molecular stacking in the films of acceptors, and the CCL values of the (010) diffraction in the OOP direction are 33.09, 48.62, and 49.92 Å for the neat 2Th-2F, BTh-Th-2F, and 2BTh-2F films, respectively. Hence, the 2BTh-2F film shows the highest crystalline quality with the shortest π-π stacking distance, which facilitates charge transport in the active layer.…”

Section: Giwaxs Characterizationmentioning

confidence: 99%

Simple Nonfused Ring Electron Acceptors with 3D Network Packing Structure Boosting the Efficiency of Organic Solar Cells to 15.44%

Wang

Lü

Liu

et al. 2021

Advanced Energy Materials

137

122

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Zhan et al. reported a fused ring electron acceptor (FREA) ITIC with an acceptordonor-acceptor (A-D-A) type structure. [1] Subsequently, numerous FREAs are developed by researchers, which largely promoted the photovoltaic performance of OSCs. Recently, Zou et al. developed a series of A-DA′D-A type FREAs (Y6 series). Up to now, the highest power conversion efficiency (PCE) of OSCs based on FREAs has reached 18%, demonstrating the bright future for practical application. [2][3][4][5][6][7][8][9] Although FREAs can achieve high efficiency, they are expensive and their syntheses are complicated, which usually includes low-yield ring-closure reactions. For the commercialization of OSCs, it is highly desired to develop highperformance and low-cost nonfullerene acceptors. Therefore, we want to develop simple nonfused ring electron acceptors (NFREAs) to replace the high-cost FREAs. In 2017, we first postulated and proved that intramolecular noncovalent interactions could be used to partially replace chemical bonds to synthesize NFREAs. [10] Since then, small fused ring building blocks such as indacenodithiophene (IDT), [11][12][13][14] cyclopentadithiophene (CPDT), [15][16][17][18][19][20][21][22][23][24] etc., were often used for the construction of NFREAs. Later, researchers also developed fully nonfused ring electron acceptors. [25][26][27] However, the photovoltaic performance of the solar cells based on NFREAs is still far behind the FREAs.Typical FREAs consist of a fused ring core, side chains, and two electron-withdrawing terminal groups. [28][29][30][31] The planar fused ring core is beneficial for the electron delocalization. The side chain can increase the solubility and affect the molecular stacking of acceptors. The electron-withdrawing terminal group such as 3-(1,1-dicyanomethylene)-5,6-difluoro-1-indanone can induce a strong intramolecular charge transfer (ICT) effect in the acceptor molecule, which can remarkably broaden the absorption, lower the energy levels (especially the lowest unoccupied molecular orbital (LUMO)), and enhance the molecular stacking. [32][33][34] Besides these basic characteristics, recent reports begin to focus on molecular stacking model. There is growing evidence that high-performance FREAs possess a 3D network packing structure, being in favor of facilitating multiple charge transport, achieving small exciton binding energy, and reducing energy loss in OSCs. [5,[35][36][37][38][39] Unlike rigid FREAs, the molecular Three nonfused ring electron acceptors (NFREAs; 2Th-2F, BTh-Th-2F, and 2BTh-2F) with thieno[3,2-b]thiophene bearing two bis(4-butylphenyl)amino substituents as the core, 3-octylthiophene or 3-octylthieno[3,2-b]thiophene as the spacer, and 3-(1,1-dicyanomethylene)-5,6-difluoro-1-indanone as the terminal group are designed and synthesized. The molar extinction coefficient of acceptors and the electron mobility of blend films gradually increase with increasing π-conjugation length. Moreover, 2BTh-2F displays a planar molecular conformation assisted by S•••N and S•••O intr...

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Section: Giwaxs Characterizationmentioning

confidence: 99%

Simple Nonfused Ring Electron Acceptors with 3D Network Packing Structure Boosting the Efficiency of Organic Solar Cells to 15.44%

Wang

Lü

Liu

et al. 2021

Advanced Energy Materials

137

122

View full text Add to dashboard Cite

show abstract

“…This rapid development is not only related to the emergence of new photovoltaic materials, but also inextricably tied to the optimization of molecular stacking and aggregation of organic semiconductors within the photoactive layer. [ 8–13 ] Nevertheless, the commercialization of OSCs not only depends on device PCE but also critically relies on their stability, [ 14 ] which is affected by the chemical structure and photosensitivity of the photoactive materials, photo‐oxidation, temperature‐induced phase transition, and degradation evoked at the electrode interface. [ 15–20 ]…”

Section: Introductionmentioning

confidence: 99%

Simultaneously Enhanced Efficiency and Operational Stability of Nonfullerene Organic Solar Cells via Solid‐Additive‐Mediated Aggregation Control

Zhang

Cai

Guo

et al. 2021

Small

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The additive strategy is widely used in optimizing the morphology of organic solar cells (OSCs). The majority of additives are liquid with high boiling points, which will be trapped within device and consequently deteriorate performance during operation. In this work, solid but volatile additives 2‐(4‐fluorobenzylidene)‐1H‐indene‐1,3(2H)‐dione (INB‐F) and 2‐(4‐chlorobenzylidene)‐1H‐indene‐1,3(2H)‐dione (INB‐Cl) are designed to replace the common 1,8‐diiodooctane (DIO) in nonfullerene OSCs. These additives present during solution casting but evaporate after moderate heating. Molecular dynamics simulations show that they can reduce the adsorption energy to improve π‐π stacking among nonfullerene acceptor (NFA) molecules, an effect that enhances light absorption and electron mobility. Both INB‐F and INB‐Cl enhance efficiency, with INB‐F achieving a maximum efficiency of 16.7% from 15.1% of the reference PBDB‐T‐2F (PM6):BTP‐BO‐4F (Y6‐BO) cell, and outperforming DIO. Remarkably, they can simultaneously enhance the operational stability, with the INB‐F‐treated OSC maintaining over 60% of the initial efficiency after 1000 h operation, demonstrating a T80 lifetime of 523 h, which is a significant improvement over T80 values of 66.2 h for the reference and 6.6 h for DIO‐treated OSC. The simultaneously enhanced efficiency and operational lifetime are also effective in PM6:BTP‐BO‐4Cl (Y7‐BO) OSCs, demonstrating a universal strategy to improve the performance of OSCs.

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“…When all the four alkyl substituents were branched (2-ethylhexyl, 2-butyloctyl, and 2-decyltetradexy for 9-9a , b , and c ), the derivative with medium-length chains ( 9-9b ) performed the best to afford PCEs up to 16.00% in BHJ OPVs with PM6 (entries 9-26–28). 160 Either shorter alkyl ( 9-9a , PCE = 11.16%) or longer alkyl chains ( 9-9c , 8.89%) resulted in inferior performance. The authors pointed out that 9-9b formed π–π stacking with a spacing of 3.45 Å, which was shorter than the corresponding values of 9-9a (3.51 Å) and 9-9c (4.08 Å).…”

Section: Substituents Of Other π-Conjugated Systemsmentioning

confidence: 98%

Impact of substituents on the performance of small-molecule semiconductors in organic photovoltaic devices via regulating morphology

Suzuki

Won

et al. 2022

J. Mater. Chem. C

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Control over π-π stacking of heteroheptacene-based nonfullerene acceptors for 16% efficiency polymer solar cells

Cited by 96 publications

References 54 publications

Simple Nonfused Ring Electron Acceptors with 3D Network Packing Structure Boosting the Efficiency of Organic Solar Cells to 15.44%

Simple Nonfused Ring Electron Acceptors with 3D Network Packing Structure Boosting the Efficiency of Organic Solar Cells to 15.44%

Simultaneously Enhanced Efficiency and Operational Stability of Nonfullerene Organic Solar Cells via Solid‐Additive‐Mediated Aggregation Control

Impact of substituents on the performance of small-molecule semiconductors in organic photovoltaic devices via regulating morphology

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