Thiourea-Assisted Facile Fabrication of High-Quality CsPbBr<sub>3</sub> Perovskite Films for High-Performance Solar Cells
Jiayu Bi, Jiarun Chang, Lei Miao, Wei Zhang, Fanning Meng, Guiqiang Wang
Abstract
Inorganic CsPbBr3 perovskite solar cells have attracted widespread attention recently because of their decent efficiency and good ambient stability. Nevertheless, the fabrication of high-quality CsPbBr3 perovskite via the conventional solution-processing strategy still faces great challenges because the solubility of CsBr in the conventional solvent is poor. Here, we develop a facile thiourea-assisted two-step spin-coating process to fabricate a CsPbBr3 perovskite film with high phase purity and crystallinity and enlarged crystal grains. Thiourea is introduced into the PbBr2 layer during the first-step spin-coating process, which promotes the wettability of the PbBr2 layer and produces the space for growing large perovskite grains. The green high-concentration CsBr/H2O solution is adopted at the second-step spin-coating process, enabling enough CsBr to be deposited by a facile one-step process. By optimizing the content of thiourea, a compact CsPbBr3 perovskite film with a smooth surface, large grains, and high phase purity and crystallinity is formed. Consequently, the fabricated perovskite solar cell with the architecture of FTO/TiO2/CsPbBr3 film/carbon exhibits a superior performance with a high efficiency of 9.11%. In addition, the unencapsulated device preserves over 90% of its initial efficiency after storage at ambient conditions for 45 days.