A sustainable solvent system for processing CsPbBr3 films for solar cells via an anomalous sequential deposition route

Abstract

Toxic solvents used in the fabrication of perovskite films are a non-ignorable obstacle for the commercialization of perovskite solar cells (PSCs). CsPbBr₃ based solar cells have attracted increasing attention due to their high stability in ambient air. Usually, a traditional sequential deposition route is employed to fabricate CsPbBr₃ films, in which toxic DMF and methanol are separately used to dissolve PbBr₂ and CsBr. In order to eliminate the solvent toxicity during the fabrication of CsPbBr₃ films, we develop an anomalous sequential deposition route to prepare CsPbBr₃ films. In this new route, a green solvent system composed of water with the addition of appropriate ethanol and ethylene glycol (EG) is developed to prepare the CsBr solution, and a green solvent, triethyl phosphate (TEP), is used to prepare the PbBr₂ solution. Different from those obtained by the traditional sequential deposition route, CsBr films are firstly prepared from their solution, then reacted with PbBr₂ through a dynamic spin-coating process, and subsequently transformed to CsPbBr₃ films via annealing treatment. As a result, solar cells based on the device configuration of FTO/TiO₂/CsPbBr₃/carbon exhibit a power conversion efficiency of 6.86%, which is comparable to that of the PSCs prepared through the traditional sequential deposition route using toxic solvents. This work provides an environment-friendly route to prepare CsPbBr₃ perovskite solar cells without efficiency loss.