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

Recently, SnO2 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 SnO2 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/SnO2 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 SnO2 nanocrystals and passivate perovskite defects at SnO2/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 SnO2 with functional molecules toward efficient and stable PSCs is provided.