Functional molecule modified SnO2 nanocrystal films toward efficient and moisture-stable perovskite solar cells

Recently, SnO 2 is widely used as an attractive electron transport layer in n-i-p planar perovskite solar cells (PSCs) due to its wide bandgap, high transmission, high carrier mobility , favorable band alignment and low annealing temperature. However, a commercial SnO 2 colloid solution suffers from soft agglomerate under long-term storage. Produced film pinholes and oxygen vacancy defect can increase non-radiative recombination at the perovskite/SnO 2 interface limiting the power conversion efficiency (PCE) and stability. Here, amino acid (glycine and alanine) and ammonium salt (ammonium titanium fluoride) are employed to modify SnO 2 nanocrystals and passivate perovskite defects at SnO 2 /perovskite film. The PCE of glycine (GLY) modified device was 19.71% and hysteresis was suppressed compared with that of 16.21% for control device. After 15-day aging at 85% relative humidity (RH), the encapsulated GLY modified device and control device retain 83.58% and 74.52% of their initial efficiency, respectively. Finally a perspective on how to modify SnO 2 with functional molecules toward efficient and stable PSCs is provided.