Thiocyanate assisted nucleation for high performance mix-cation perovskite solar cells with improved stability

We demonstrated a high performance MA(0.6)FA(0.4)PbI(x)Br(1-x) mix-cation perovskite solar cell with thiocyanate assisted nucleation on low temperature processed SnO2 electron transport layer by gas-quenching deposition. The perovskite solar cell with thiocyanate additive exhibited enlarged grain size closed to 1 mu m with improved power conversion efficiency (PCE) and better device stability. With the aid of thiocyanate additive, the champion cell has achieved the PCE of 19.64% with fill factor over 75%. Moreover, the SCN- assisted device showed considerably improved stability which retained 90% of its original PCE after degradation for 28 days, while the control device suffered 10% PCE loss after 14 days. Characterizations such as current density - voltage, electron microscopy (SEM, c-AFM, KPFM) and space-charge limited current-voltage (SCLC) measurements have been conducted for investigating the mechanism behind. The superior performance of SCN- assisted perovskite is owning to enlarged grain interiors as well as passivated grain boundaries, which attributed to the reduced current leakage, enhanced charge transport characteristics, and less trap-assisted interfacial recombination in the device.