Upgrading Spiro-OMeTAD with β-Chloroethylcarbazole to Improve the Stability of Perovskite Solar Cells
Jialin Wang, Haizhou Lu, Yuhang Liu, Yuhang Liu, Pengyang Wang, Sanlong Wang, Xiyue Dong, Ying Zhao, Yongsheng Liu, Yongsheng Liu, Michaël Grätzel, Xiaodan Zhang
Abstract
Spiro-OMeTAD has served as a crucial hole transporting material (HTM) in the advancement of efficient perovskite solar cells (PSCs). However, the diminished thermal stability of lithium-doped Spiro-OMeTAD (Li-Spiro) has been a limiting factor, leading to a significant decline of the power conversion efficiency (PCE) and stability, particularly at a temperature exceeding 65 °C. Here, we report an upgraded HTM, Spiro-OMeCzCl, by incorporating chloroethyl-modified carbazole units to expand the conjugated area of the donor group. This novel configuration significantly enhances the thermal stability and film quality. The resulting PSCs utilizing Spiro-OMeCzCl achieved a high PCE of 24.6%, coupled with exceptional long-term stability. The target cells maintained approximately 95% of their initial PCE after 57 days under a nitrogen atmosphere. Importantly, in subsequent thermal stability tests involving a gradual temperature increase, the cells sustained an average PCE of over 85% after 200 h at temperatures ranging from 60 to 90 °C.