A terthieno[3,2‐b]thiophene (6T) based fused‐ring low bandgap electron acceptor, 6TIC, is designed and synthesized for highly efficient nonfullerene solar cells. The chemical, optical, and physical properties, device characteristics, and film morphology of 6TIC are intensively studied. 6TIC shows a narrow bandgap with band edge reaching 905 nm due to the electron‐rich π‐conjugated 6T core and reduced resonance stabilization energy. The rigid, π‐conjugated 6T also offers lower reorganization energy to facilitate very low V_OC loss in the 6TIC system. The analysis of film morphology shows that PTB7‐Th and 6TIC can form crystalline domains and a bicontinuous network. These domains are enlarged when thermal annealing is applied. Consequently, the device based on PTB7‐Th:6TIC exhibits a high power conversion efficiency (PCE) of 11.07% with a high J_SC > 20 mA cm⁻² and a high V_OC of 0.83 V with a relatively low V_OC loss (≈0.55 V). Moreover, a semitransparent solar cell based on PTB7‐Th:6TIC exhibits a relatively high PCE (7.62%). The device can have combined high PCE and high J_SC is quite rare for organic solar cells.

中文翻译：

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基于Terthieno [3,2-b]噻吩（6T）的低带隙熔融环电子受体，用于高效太阳能电池，具有高短路电流密度和低开路电压损耗

设计并合成了基于叔硫诺[3,2- b ]噻吩（6T）的稠环低带隙电子受体6TIC，用于高效非富勒烯太阳能电池。深入研究了6TIC的化学，光学和物理特性，器件特性和薄膜形态。6TIC显示出一个窄的带隙，由于富电子的π共轭6T核和降低的共振稳定能，带隙达到了905 nm 。刚性的π共轭6T还提供了较低的重组能量，以促进6TIC系统中非常低的V _OC损失。对膜形态的分析表明PTB7-Th和6TIC可以形成晶畴和双连续网络。当应用热退火时，这些区域会扩大。因此，基于PTB7-Th：6TIC的器件具有11.07％的高功率转换效率（PCE），具有较高的J _SC > 20 mA cm ^-2和具有0.83 V的高V _OC，且具有较低的V _OC损耗（ ≈0.55 V）。此外，基于PTB7-Th：6TIC的半透明太阳能电池具有相对较高的PCE（7.62％）。该设备可以结合使用高PCE和高J _SC 对于有机太阳能电池来说非常罕见。