ZnO-Assisted Growth of CHNHPbICl Film and Efficient Planar Perovskite Solar Cells with a TiO/ZnO/C Electron Transport Trilayer.

Appropriate electron transport layers (ETL) are essential in perovskite solar cells (PSCs) with high power conversion efficiency (PCE). Herein, a TiO/ZnO/C trilayer fabricated on a transparent fluorine-doped tin oxide (FTO) glass substrate is used as a compound ETL in planar PSCs. The trilayer shows positive effects on both perovskite synthesis and device performance. The ZnO layer assists growth of CHNHPbICl ( x ≈ 0) annealed at a lower temperature and with a shorter time, which is due to a more rapid and easier decomposition of the intermediate CHNHPbCl phase in the growth of CHNHPbICl . All three materials in the trilayer are important for obtaining PSCs with a high PCE. ZnO is critical for enhancing the open circuit voltage by ensuring proper energy alignment with the TiO and C layers. C enhances carrier extraction from the CHNHPbICl layer. TiO eliminates charge recombination at the FTO surface and ensures efficient electron collection. The best-performing PSC based on the TiO/ZnO/C electron transport trilayer features a PCE of 18.63% with a fill factor of 79.12%. These findings help develop an understanding of the effects of ZnO-containing ETLs on perovskite film synthesis and show promise for the future development of high-performance PSCs with compound ETLs.