Interface Regulation for Efficient and Stable Perovskite Solar Cells through Potassium Citrate Molecules

Efficiency and stability are key factors determining the final cost of electricity that perovskite solar cells (PSCs) generate. To date, effective strategy to progress in achieving efficient and stable PSCs is still a difficult problem that researchers continue to explore. This study reports a useful way to improve the quality of SnO2 film by introducing potassium citrate (PC) into SnO2 nanoparticles solution. PC passivates interface defects between perovskite and SnO2 layers via the interactions of functional groups (K+, -COO-) in PC with undersaturated Pb and I ions in perovskite and Sn4+ in SnO2. The resultant photovoltaic (PV) device achieves a champion power conversion efficiency (PCE) of 22.79 %. The introduction of PC interface also significantly suppress the degradation of PSCs, by which 87.6 % of initial PCE is maintained after 2850 h storage in ambient environment. Moreover, the devices retained 95.5 % of initial PCE under 1-sun continuous illumination for 1000 h.