Performance enhancement of perovskite solar cells by doping non-toxic multifunctional natural sodium lignosulfonate into SnO2

The buried interface between perovskite and the electron transport layer (ETL) played a crucial role in improving the power conversion efficiency (PCE) and stability of n-i-p structured perovskite solar cells (PSCs). Commercially prepared SnO2-based ETL films often suffered from severe interface defects, imperfect energy level alignment, and uncontrollable perovskite nucleation sites, hindering the achievement of highly efficient and stable PSCs. In this study, the hindering factors of commercial SnO2 ETL films were all addressed by the incorporation of a non-toxic multifunctional molecule, natural sodium lignosulfonate (SL) into the SnO2 ETL precursor, and ameliorated perovskite films were obtained. As a result, the PCE of a reference device (19.60%) was improved to 21.12% after doping with SL. Furthermore, unencapsulated SL-doped devices exhibited excellent environmental stability. After 840 h of storage at ∼20% RH, the SL-modified device retained ∼83% of its initial PCE, well exceeding the control device (∼13%). In addition, our findings suggest a novel strategy aimed at improving the efficiency and stability of PSCs by the incorporation of non-toxic multifunctional molecules such as natural SL.