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

Abstract

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.