Effective passivation of defects in high-performance tin oxide-based perovskite solar cells using guanidinium phosphate additives

Perovskite solar cells (PSCs) have been extensively studied owing to their excellent photovoltaic performance. Tin oxide (SnO2) is an ideal electron transport material for PSCs. However, owing to nanoparticle agglomeration and defects, the excellent performance of SnO2 cannot be effectively utilized. In this article, a multifunctional additive guanidinium phosphate (GP) is introduced into SnO2. The modification of GP not only improves the surface properties of the electron transport layer (ETL) and the crystalline quality of the perovskite layer (PVK), but also passivates the double-sided defects and suppresses the non-radiative carrier recombination, as well as enhances the electron extraction ability and harmonizes the energy level alignment between the ETL and PVK. Consequently, the GP-modified device achieves a power conversion efficiency (PCE) of 23.91 % and a fill factor (FF) of up to 83.45 %. In addition, the unencapsulated device maintains over 90 % of its starting efficiency after being aged under 25 degree celsius and 40 +/- 10 % relative humidity (RH) for 1000 h. The results demonstrate that the introduction of GP is an effective strategy to enhance the performance and stability of PSCs.