Upgrading\nSpiro-OMeTAD with β‑Chloroethylcarbazole\nto Improve the Stability of Perovskite Solar Cells

Spiro-OMeTAD has served as a crucial hole transporting\nmaterial\n(HTM) in the advancement of efficient perovskite solar cells (PSCs).\nHowever, the diminished thermal stability of lithium-doped Spiro-OMeTAD\n(Li-Spiro) has been a limiting factor, leading to a significant decline\nof the power conversion efficiency (PCE) and stability, particularly\nat a temperature exceeding 65 °C. Here, we report an upgraded\nHTM, Spiro-OMeCzCl, by incorporating chloroethyl-modified carbazole\nunits to expand the conjugated area of the donor group. This novel\nconfiguration significantly enhances the thermal stability and film\nquality. The resulting PSCs utilizing Spiro-OMeCzCl achieved a high\nPCE of 24.6%, coupled with exceptional long-term stability. The target\ncells maintained approximately 95% of their initial PCE after 57 days\nunder a nitrogen atmosphere. Importantly, in subsequent thermal stability\ntests involving a gradual temperature increase, the cells sustained\nan average PCE of over 85% after 200 h at temperatures ranging from\n60 to 90 °C.