Inorganic salts released from polypyrrole nanocapsules on compact TiO2 layer for highly efficient inorganic CsPbI3-type perovskite solar cells

• Published in: Chemical engineering journal (Lausanne, Switzerland : 1996) Vol. 497; p. 154845
• Main Authors: Li, Dan, Li, Xin, Wang, Kang, Ma, Simin, Shao, Xin, Yang, Tingting, Han, Yunhui, Zhang, Zhengguo, Liu, Shengzhong, Guo, Shengwei
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.10.2024
• Subjects: CsPbI3 solar cells; Efficiency; LiCl@ PPy NCPs; planar TiO2; Stability; CsPbI3 solar cells; Stability; Efficiency; planar TiO2; LiCl@ PPy NCPs
• ISSN: 1385-8947
• DOI: 10.1016/j.cej.2024.154845

•The inorganic salts were liberated from PPy NCPs shell during the CsPbI3 precursor film annealing process.•The liberated LiCl can deactivate point defects, optimize the energy level at the TiO2/perovskite interface, and enhance CsPbI3 crystallinity.•Compared to NaCl@PPy NCPs-TiO2, ZnCl2@PPy NCPs-TiO2, and pristine TiO2 films, the LiCl@PPy NCPs-TiO2 exhibited superior electron conductivity and the highest Fermi level.•The CsPbI3 PSCs with LiCl@PPy NCPs-TiO2 ETL achieved excellent performance and stability. The compact TiO2 serves as a crucial electron transport layer (ETL) for fabricating high-efficiency CsPbI3 solar cells. Modifying TiO2 with inorganic ions is regarded as a simple and effective method to optimize the band energy level, eliminate interface defects, and enhance the crystallinity of the CsPbI3 film. However, inorganic ions risk being washed away by perovskite solvents such as DMF and DMSO. In this work, core–shell inorganic salt (LiCl, NaCl, ZnCl2)@polypyrrole nanocapsules (PPy NCPs) were fabricated as a buffer layer at the interface of TiO2/CsPbI3 layer. The inorganic salts are released from PPy NCPs during the annealing process of the CsPbI3 precursor film, thereby preventing them from being washed away by the DMF/DMSO solvents. Compared to NaCl@PPy NCPs-TiO2, ZnCl2@PPy NCPs-TiO2, and pristine TiO2 films, the LiCl@PPy NCPs-TiO2 exhibited the best electron conductivity and highest Fermi level. The released LiCl not only passivates point defects in TiO2 by forming Li-O-Ti bonds, optimizing the energy level at the TiO2/perovskite interface, but also incorporates into the CsPbI3 lattice, improving its crystallinity. As a result, solar cells based on LiCl@PPy NCPs-TiO2 layer demonstrated a higher PCE of 19.78 %, along with increased open-circuit voltage (VOC) and fill factor (FF) values of 1.161 V and 83.1 %, respectively. Furthermore, the LiCl@PPy NCPs-TiO2 layer also enhanced the stability of CsPbI3 solar cells under humidity conditions.