Ternary polymer solar cells based on a thiazolothiazole-based polymer donor (PTzBT) and a fullerene acceptor (PC₆₁BM) have attracted attention because they show high efficiency and stability by addition of a non-fullerene acceptor (ITIC). However, the performance improvement mechanism is not completely elucidated. Here, we show the stability improvement mechanism due to less charge accumulation in the PTzBT cells with ITIC using operando electron spin resonance from a microscopic viewpoint. We observed two correlations between device performance and number of spins (N_spin) under solar irradiation. One correlation is the decrease in short-circuit current and the N_spin increase in electrons on PC₆₁BM and holes in PTzBT, where the ITIC addition causes the less these N_spin. The other correlation is the increase in open-circuit voltage and the N_spin decrease in holes in ZnO. These findings explain the stability improvement mechanism, showing the correlation between less charge accumulation and higher stability, which is valuable for the development of further efficient and stable polymer solar cells.

基于噻唑并噻唑基聚合物供体（PTzBT）和富勒烯受体（PC ₆₁ BM）的三元聚合物太阳能电池因其通过添加非富勒烯受体（ITIC）而表现出高效率和稳定性而受到关注。然而，性能改进机制并未完全阐明。在这里，我们从微观角度展示了使用操作电子自旋共振在具有 ITIC 的 PTzBT 电池中由于较少的电荷积累而提高稳定性的机制。我们观察到太阳辐射下器件性能和自旋数 ( N _{spin ) 之间的两种相关性。}一种相关性是短路电流的减少和PC _{61上电子的}N_自旋增加BM 和 PTzBT 中的空穴，其中 ITIC 添加导致这些N_自旋较少。另一个相关性是开路电压的增加和 ZnO 中空穴的N_自旋减少。这些发现解释了稳定性改善机制，显示了较少的电荷积累和较高的稳定性之间的相关性，这对于开发更高效和稳定的聚合物太阳能电池具有重要价值。