Carboxymethyldextran Sodium Modified SnO2 Enables High Efficient and Stable Perovskite Solar Cells with high fill factor of 84.89 %

SnO2-based perovskite solar cells (PSCs) have made tremendous progress, but there's still a lot of room for optimization of the fill factor and power conversion efficiency compared with the short-circuit current density and open-circuit voltage. The fill factor is strongly related with carrier extraction and transport efficiency. In this study, a simple method for passivating the SnO2 by integrating Carboxymethyldextran Sodium (CMD) into the SnO2 colloidal mixture was presented. It is shown that the addition of CMD can improve the electronic property 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 %, the fill factor (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 photovoltaic conversion efficiency (PCE) after 1000 hours of storage. This study provides a low-cost, convenient and efficient method for realizing efficient and stable PSCs.