Interface modification effects using a halide-free lead source for perovskite solar cells

The remnant PbI2 at the mesoporous-TiO2 (m-TiO2)/CH3NH3PbI3 interface can act as an interface modification layer for high-efficiency perovskite solar cells (PSCs). In this study, we adopted Pb(CH3COO)2·3H2O (PbAc2) to control the amount of remnant PbI2 at the m-TiO2/CH3NH3PbI3 interface. The characterization results demonstrate that the amount of remnant PbI2 could be controlled by the concentration of PbAc2 solution without influencing the crystallographic textures of CH3NH3PbI3 films. By adjusting the PbAc2 solution concentration, the optimized PSC can achieve a 15% enhancement of PCE in the case of using a two-step method for CH3NH3PbI3 preparation. Under the circumstances of using an anti-solution method, it still displayed a 10% enhancement of the average PCE for 10 individual PSCs with PbAc2 (13.6% to 15.0%). The steady-state photoluminescence (PL), time-resolved photoluminescence (TR-PL) and open-circuit voltage decay results demonstrated that the remnant PbI2 could reduce carrier recombination at the m-TiO2/CH3NH3PbI3 interface. Meanwhile, the enhancement of the open-circuit voltage was achieved for PSCs with PbAc2.