A Noncovalently Fused‐Ring Asymmetric Electron Acceptor Enables Efficient Organic Solar Cells

Abstract

Main observation and conclusion Recently, the asymmetric nonfullerene acceptors (NFAs) with acceptor‐donor‐acceptor (A‐D‐A) structure have been developed rapidly, especially for the modification of asymmetric core, asymmetric side chains and asymmetric end groups. In this work, a novel asymmetric A‐D‐π‐A type NFA with a noncovalently fused‐ring core named PIST‐4F is synthesized, containing an indacenodithieno[3,2‐b]dithiophene (IDT), two strong electron‐withdrawing end groups and an alkylthio‐substituted thiophene π‐bridge. Benefiting from the S···S noncovalent interaction between the sulfur atom on π‐bridge and the adjacent thiophene in IDT, the PIST‐4F presents nearly planar geometry and extended conjugated area, resulting in the optimized electronic properties, charge transport, and film morphology compared to the symmetric NFA PI‐4F. As a result, PM6:PIST‐4F‐based devices achieve a higher power conversion efficiency (PCE) of 13.8%, while the PM6:PI‐4F‐based devices only show a PCE of 7.1%. Notably, the PM6:PIST‐4F‐based devices processed with nonhalogen solvent toluene exhibit an excellent PCE as high as 13.1%. These results indicate that PIST‐4F is an effective acceptor for high‐efficiency organic solar cells.

Manipulating the Intermolecular Interactions through Side Chain Engineering and Unilateral π‐Bridge Strategy for Efficient Small Molecular Photovoltaic Acceptor

“…This reserved planar molecular conformation is attributed to the noncovalent weak interactions as often observed in SMAs with π-bridges, especially in the rising nonfused SMA fields. [39][40][41][42][43] Besides, the introduction of unilateral π-bridge induces asymmetrical electron cloud distributions (Figure S2, Supporting Information), accounting for markedly raised dipole moment from 0.46 Debye (ID-C6Ph-4F) to 2.44 Debye. Therefore, the preferred molecular planarity and larger dipole moment of ID-C6Ph-ST-4F could exert better molecular assembly than that of analog absent of π-bridge.…”

“…[25,37,38] Consequently, several A-D-π-A type SMAs were investigated. [39,40] Typically, one alkythio-substituted thiophene bridge was inserted into highly crystalline ID-4F. [39] The resulting A-D-π-A type acceptor IDST-4F received redshifted absorption by over 70 nm and elevated energy levels, and PM6/IDST-4F based solar cells generated enhanced J SC up to 24.9 mA cm −2 and PCE of 14.3%.…”

From Perylene Diimide Polymers to Fused‐Ring Electron Acceptors: A 15‐Year Exploration Journey of Nonfullerene Acceptors

“…(1) The design of a high‐performance molecule is based on detailed structure‐property relationships, thus the effects of structural variation on exciton generation/diffusion/separation, charge transport/recombination, molecular packing and morphology, [ 117 ] energy loss [ 117 ] and stability [ 118 ] should be further investigated to build a solid foundation for the design of ideal materials with high efficiency and stability. Furthermore, investigations on low‐cost, scale‐up and eco‐friendly synthesis of active materials are also necessary, for example, noncovalently FREA [ 119‐123 ] and organotin‐free synthesis [ 124 ] . (2) The effects of processing methods on morphology and device performance [ 125‐126 ] and fabrication technologies adapting to large‐area, flexible and semitransparent devices/modules should be further explored (Figure 11b).…”

Research Progress in Degradation Mechanism of Organic Solar Cells

“…通过给体和受体化学键合的单组分材料 SCP3, 在光照和 90 ℃储存下几乎没有性能衰减, 甚至在 160 ℃下储存 400 h 后性能几乎保持在同一水平 [135] . 氟 化策略 [142][143] 以及不对称合成 [144][145] 等能够影响分子偶 极从而改善分子堆积, 在提高器件性能和稳定性方面显 示出良好的优势. Xin 等 [143] 通过对 ITIC 侧链不同位置进 行氟取代研究了侧链对活性层稳定性的影响, 间位氟取 代受体 mF-ITIC 在 150 ℃退火 96 h 后保留初始效率的 92%, 而邻位取代的 oF-ITIC 和 ITIC 仅保留 82%和 67%, 表明侧链位置能够影响材料结晶性, 从而造成器件热稳 定性的差异.…”