The exploration of high-performance and low-cost wide-bandgap polymer donors remains critical to achieve high-efficiency nonfullerene organic solar cells (OSCs) beyond current thresholds. Herein, the 1,2,3-benzothiadiazole (iBT), which is an isomer of 2,1,3-benzothiadiazole (BT), is used to design wide-bandgap polymer donor PiBT. The PiBT-based solar cells reach efficiency of 19.0%, which is one of the highest efficiencies in binary OSCs. Systemic studies show that isomerization of BT to iBT can finely regulate the polymers’ photoelectric properties including i) increasing the extinction coefficient and photon harvest, ii) downshifting the highest occupied molecular orbital energy levels, iii) improving the coplanarity of polymer backbones, iv) offering good thermodynamic miscibility with acceptors. Consequently, the PiBT:Y6 bulk heterojunction (BHJ) device simultaneously reaches advantageous nanoscale morphology, efficient exciton generation and dissociation, fast charge transportation, and suppressed charge recombination, leading to larger V_OC of 0.87 V, higher J_SC of 28.2 mA cm⁻², greater fill factor of 77.3%, and thus higher efficiency of 19.0%, while the analog-PBT-based OSCs reach efficiency of only 12.9%. Moreover, the key intermediate iBT can be easily afforded from industry chemicals via two-step procedure. Overall, this contribution highlights that iBT is a promising motif for designing high-performance polymer donors.

中文翻译：

---

苯并噻二唑异构化产生有前景的聚合物供体和效率为 19.0% 的有机太阳能电池

探索高性能和低成本的宽带隙聚合物供体对于实现超越当前阈值的高效非富勒烯有机太阳能电池（OSC）仍然至关重要。在此，1,2,3-苯并噻二唑（iBT）是2,1,3-苯并噻二唑（BT）的异构体，用于设计宽带隙聚合物供体PiBT。基于 PiBT 的太阳能电池的效率达到 19.0%，这是二元 OSC 中效率最高的之一。系统研究表明，BT 异构化为 iBT 可以精细调节聚合物的光电性能，包括 i) 增加消光系数和光子收获，ii) 降低最高占据分子轨道能级，iii) 提高聚合物主链的共面性，iv)与受体具有良好的热力学混溶性。因此，PiBT:Y6本体异质结（BHJ）器件同时达到了有利的纳米级形貌、高效激子生成和解离、快速电荷传输和抑制电荷复合，从而导致更大的VOC _（ 0.87 V）和更高的J _SC（28.2 mA cm ^{-）如图 2}所示，填充因子达到 77.3%，从而效率提高到 19.0%，而基于模拟 PBT 的 OSC 的效率仅为 12.9%。此外，关键中间体 iBT 可以通过两步程序从工业化学品中轻松获得。总的来说，这一贡献凸显了 iBT 是设计高性能聚合物供体的一个有前途的主题。