All Green Solvents for Fabrication of CsPbBr<sub>3</sub> Films for Efficient Solar Cells Guided by the Hansen Solubility Theory
Xiaobing Cao, Guoshuai Zhang, Yifan Cai, L. Jiang, Xin He, Qingguang Zeng, Jinquan Wei, Yi Jia, Guichuan Xing, Wei Huang
Abstract
Toxic solvents used in the fabrication of perovskite solar cells are an obstacle for their commercialization. Replacing those toxic solvents with green solvents is very important for both ecological environment safety and the health of operators working in manufactory and labs. CsPbBr 3 ‐based solar cells have attracted increasing attention due to its high stability. Herein, high‐quality CsPbBr 3 films are prepared using all green solvents based on a two‐step spin‐coating method. In the first step, a green solvent system of polyethylene glycol (PEG) with the addition of γ‐butyrolactone is used for preparing PbBr 2 solutions by matching the Hansen solubility parameters (HSPs) between PbBr 2 and the mixed solvent system. By optimizing the HSPs and viscosity, a new complex of PbBr 2 ·(PEG) is formed by spin‐coating from the PbBr 2 solution, followed by acetic acid dropping while spinning. In the second step, green water is used to dissolve CsBr to prepare a high concentration CsBr/H 2 O solution. High‐quality CsPbBr 3 films with full coverage are obtained by spin‐coating CsBr/H 2 O solution onto the PbBr 2 ·(PEG) films after annealing. As a result, a solar cell with configuration of fluorine‐doped tin oxide/TiO 2 /CsPbBr 3 /carbon exhibits a power conversion efficiency of 8.11% due to its high‐quality harvest layer.