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

CsPbBr 3 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 CsPbBr 3 perovskite solar cells (PSCs). In this study, we utilized methanol as an anti-solvent of the CsBr/H 2 O solution to regulate the detrimental effects of water on the CsPbBr 3 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 CsPbBr 3 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 CsPbBr 3 PSCs to improve the wettability of PbBr 2 towards the CsBr/H 2 O solution and ensure the formation of pure-phase CsPbBr 3 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 CsPbBr 3 PSCs prepared with water as a solvent. Importantly, this approach significantly reduces the reliance on methanol compared to conventional fabrication methods for CsPbBr 3 PSCs. Overall, this work presents a promising pathway for achieving high V oc and efficiency in CsPbBr 3 PSCs by utilizing water as a solvent. CsPbBr 3 has received more and more attention in the field of optoelectronic devices due to its excellent stability.