Multifunctional buried interface modification of SnO2-based planar perovskite solar cells via phosphorus hetero-phenanthrene flame retardants.

Tin dioxide (SnO 2) is widely utilized for the cost-effective electron transport layer (ETL) in perovskite solar cells (PSCs) owing to its excellent optoelectronic properties. However, the surface defect states present in SnO 2 ETL prepared by conventional solution methods seriously hinder the further improvement of device photovoltaic performance. It is urgently essential to develop a facile strategy to effectively minimize the adverse effects of SnO 2 ETL on PSCs. Herein, a phosphorus hetero-phenanthrene flame retardant, DOPO, is introduced as a multifunctional surface modifier to improve the interfacial properties between SnO 2 ETL and perovskite. Through systematic characterization analysis, the P O group in DOPO not only passivates the defective states on the surface of SnO 2 ETL, but also provides chemical chelation sites for the uncoordinated Pb2+ ions in the upper perovskite structure to improve the film crystalline quality. Eventually, the photoelectric conversion efficiency (PCE) of the optimized device is improved from an initial 19.74 %–22.57 %, along with significantly improved device stability. This work provides an important reference for the development of new multifunctional interface modification materials required for SnO 2 -based planar PSCs with excellent properties. [ABSTRACT FROM AUTHOR]