Methanol as an anti-solvent to improve the low open-circuit voltage of CsPbBr3 perovskite solar cells prepared with water

Abstract

CsPbBr₃ has received more and more attention in the field of optoelectronic devices due to its excellent stability. To address the cost and environmental concerns associated with the use of toxic methanol, water has been explored as a substitute solvent for CsBr in the preparation of CsPbBr₃ perovskite solar cells (PSCs). In this study, we utilized methanol as an anti-solvent of the CsBr/H₂O solution to regulate the detrimental effects of water on the CsPbBr₃ film and control the crystallization process. From results of the experiment, it was found that methanol anti-solvent treatment greatly improved the crystallization of the CsPbBr₃ film, increased the grain size, and reduced the defect density. After the introduction of methanol anti-solvent treatment, the power conversion efficiency (PCE) increased from 6.09% to 7.91%, while the open-circuit voltage (V_oc) increased from 1.18 V to 1.39 V. Furthermore, we incorporated 2-hydroxyethylurea into the CsPbBr₃ PSCs to improve the wettability of PbBr₂ towards the CsBr/H₂O solution and ensure the formation of pure-phase CsPbBr₃ films. The introduction of 2-hydroxyethylurea resulted in an additional increase in V_oc from 1.19 V to 1.42 V. The PCE further improved from 6.56% to 8.62% after methanol anti-solvent treatment. These results demonstrate that methanol treatment effectively addresses the low V_oc issue observed in CsPbBr₃ PSCs prepared with water as a solvent. Importantly, this approach significantly reduces the reliance on methanol compared to conventional fabrication methods for CsPbBr₃ PSCs. Overall, this work presents a promising pathway for achieving high V_oc and efficiency in CsPbBr₃ PSCs by utilizing water as a solvent.