As known, to balance the open-circuit voltage (V_OC) and short-circuit current density (J_SC) is one of the effective strategies to improve the photovoltaic performances of OSCs. In this work, a thiophene-fused benzotriazole (BTAZT) unit acts as a “π-bridge” to build an acceptor (A3) with A-π-D-π-A structure for OSCs. Compared with a thiophene-fused benzothiadiazole (BTT) unit as a “π-bridge” in our previous acceptor (A2), BTAZT unit exhibits relatively weak electron-withdrawing ability that results in a significant uplift of LUMO energy level to favor for enhancement of V_OC. Also, the fusion of a thiophene ring onto BTAZ unit strengthens the intramolecular charge transfer to maintain the relatively high J_SC. Therefore, the PTB7-Th:A3 OSC device shows higher PCE of 11.0% with more balanced device parameters (V_OC = 0.959 V, J_SC = 17.30 mA cm⁻², FF = 66.2%) as well as smaller energy loss (E_loss) of 0.57 eV than the PTB7-Th:A2 device with PCE of 8.20% (V_OC = 0.701 V, J_SC = 19.47 mA cm⁻², FF = 60.1% and E_loss = 0.66 eV). This work indicates that the rational structural modification of a “π-bridge” for A-π-D-π-A type acceptor is an effective approach to achieve the balanced V_OC and J_SC for the OSCs.

如已知的，以平衡的开路电压（V _OC）和短路电流密度（Ĵ _SC）是提高OSC的光伏性能的有效策略之一。在这项工作中，噻吩稠合的苯并三唑（BTAZT）单元充当“π桥”，为OSC构建具有A-π-D-π-A结构的受体（A3）。与我们以前的受体（A2）中的噻吩稠合的苯并噻二唑（BTT）单元作为“π桥”相比，BTAZT单元的吸电子能力相对较弱，导致LUMO能级显着升高，有利于增强V _OC。而且，噻吩环与BTAZ单元的融合增强了分子内电荷转移，从而维持了相对较高的J_SC。因此，PTB7-Th：A3 OSC器件显示出更高的PCE为11.0％，具有更平衡的器件参数（V _OC  = 0.959 V，J _SC  = 17.30 mA cm ^-2，FF = 66.2％）以及更小的能量损耗（E相较于PCE为8.20％的PTB7-Th：A2器件（V _OC  = 0.701 V，J _SC  = 19.47 mA cm ^-2，FF = 60.1％和E_损耗 = 0.66 eV），其_损耗为0.57 eV 。这项工作表明，对A-π-D-π-A型受体的“π桥”进行合理的结构修饰是实现平衡的V _OC和J的有效方法。OSC的_SC。