Improving photovoltaic performance of CsPbBr3 perovskite solar cells by a solvent-assisted rinsing step

Abstract

CsPbBr3 perovskite solar cells (PSCs) have been extensively developing for high stability and open-circuit voltage applications. Typically, 2-propanol (IPA) is used as a rinsing solvent during the two-step dipping production process of CsPbBr3. However, we evidenced that the conventional IPA-rinsing step caused the formation of an undesirable Cs4PbBr6 phase resulting in poor surface topography and limited charge transport properties. Surface engineering using IPA-based rinsing was found to be inefficient owing to the poor solubility of CsBr in IPA. Alternative rinsing solvents such as ethanol and methanol were studied in this work. Notably, ethanol-rinsed CsPbBr3 (E-CsPbBr3) showed a pure-phase with a highly-compacted crystalline structure, based on suitable solubility. Because of the high purity of the perovskite crystal and large-size grains, charge extraction properties were improved, and the non-radiative recombination process was suppressed in E-CsPbBr3. Device fabrication demonstrated that average power conversion efficiency (PCE) increased from 4.77% to 6.56% by using ethanol as a rinsing solvent. The best-performing cell showed PCE of 6.89%, with exceptional stability with practically constant PCE after aging for 1030 h under humid ambient air. These remarkable experimental findings enable us to suggest a new standard process for the development of stable and high-performance CsPbBr3-based PSCs.