Carboxymethyldextran sodium-modified SnO2 enables highly efficient and stable perovskite solar cells with a high fill factor of 84.89%

Abstract

SnO₂-based perovskite solar cells (PSCs) have made tremendous progress, but there's still a lot of room for optimization of the fill factor (FF) and power conversion efficiency (PCE) compared with the short-circuit current density and open-circuit voltage. The FF is strongly related to carrier extraction and transport efficiency. In this study, a simple method for passivating SnO₂ by integrating carboxymethyldextran sodium (CMD) into a SnO₂ colloidal mixture is presented. It is shown that the addition of CMD can improve the electronic properties of SnO₂, reduce the nonradiative recombination, effectively passivate the defects at the buried interface of SnO₂ and perovskite, and make the device form a suitable energy level arrangement. As a result, the efficiency of this SnO₂-CMD-based device is increased from 23.09% to 24.73%, and the FF is significantly increased to 84.89%, with negligible hysteresis. At a relative humidity of 20–30% and a temperature of 25 °C, the device retains 86% of its original PCE after 1000 hours of storage. This study provides a low-cost, convenient and efficient method for realizing efficient and stable PSCs.