Fused-ring electron acceptors (FREAs) have attracted immense interest owing to their ability for facile structural modification and good thermal and optical characteristics. Among these acceptors, isomerized building blocks originating from multiple reaction sites affect the electronic structures, morphological properties and resulting photovoltaic performance, but have rarely been studied. Herein, three isomeric FREAs, Z1-aa, Z1-ab, and Z1-bb, were synthesized using different reaction sites of benzo[b]benzo[4,5]thieno[2,3-d]thiophene (BTBT)-based fused-ring cores and were used in organic solar cells (OSCs). As compared to Z1-aa and Z1-ab, Z1-bb exhibited red-shifted absorption and a higher maximum molar extinction coefficient. When blended with PM6, Z1-bb-based OSCs exhibited more balanced charge transport compared to those with the PM6:Z1-aa and PM6:Z1-ab blend films, which favored higher short-circuit current density (J_sc) and fill factor (FF). As a result, the OSC devices based on Z1-bb exhibited a power conversion efficiency (PCE) of 12.66% with V_oc = 0.98 V, J_sc = 18.52 mA cm⁻², and FF = 70.05%, respectively, which are significantly higher than the values recorded for the Z1-ab-based (PCE of 9.60%) and Z1-aa-based (PCE of 4.56%) devices. These results indicate that the isomerization of a fused-ring core originating from a special reaction site could be a promising approach to achieve high-performance OSCs with high J_sc, V_oc, and FF.

中文翻译：

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通过基于苯并[b]苯并[4,5]噻吩并[2,3-d]噻吩的八环非富勒烯受体的异构化同时改善有机太阳能电池的光伏参数

稠环电子受体（FREAs）由于其易于进行结构修饰以及良好的热学和光学特性而引起了极大的兴趣。在这些受体中，源自多个反应位点的异构化结构单元会影响电子结构，形态学性质以及由此产生的光伏性能，但很少进行研究。在此，使用苯并[ b ]苯并[4,5]噻吩并[2,3- d ]的不同反应位点合成了三个异构的FREA，Z1-aa，Z1-ab和Z1-bb。基于]噻吩（BTBT）的稠环核，并用于有机太阳能电池（OSC）。与Z1-aa和Z1-ab相比，Z1-bb表现出红移吸收和更高的最大摩尔消光系数。当与PM6混合时，与PM6：Z1-aa和PM6：Z1-ab混合膜相比，基于Z1-bb的OSC表现出更加平衡的电荷传输，这有利于提高短路电流密度（J _sc）和填充因子（FF）。结果，基于Z1-bb的OSC器件在V _oc = 0.98 V，J _sc = 18.52 mA cm ^-2时表现出12.66％的功率转换效率（PCE）。和FF = 70.05％，分别远高于基于Z1ab的设备（PCE为9.60％）和基于Z1aa的设备（PCE为4.56％）的记录值。这些结果表明，源自特殊反应位点的稠环核的异构化可能是实现具有高J _sc，V _oc和FF的高性能OSC的有前途的方法。