Hybrid Chemical Vapor Deposition of Mixed-Cation MAxFA1–xPbI3-yBry Perovskites via Lead Bromide Doping for High-Performance Photovoltaic Devices

In recent years, there has been some interest in the use of chemical vapor deposition (CVD) for the fabrication of perovskite solar cells (PSCs) due to its satisfactory film-quality, high controllability and consistency, low equipment cost, and easy industrial scale-up. In this paper, the mixed-cation MA_xFA_1–xPbI_3–yBr_y perovskite light absorbing films were first deposited via a lead bromide (PbBr₂) precursor doped CVD process, and the effect of bromine content on its material phase composition, film morphology, optical band gap, device photovoltaic characteristic, charge recombination, and carrier transport property were systematically studied. The experimental results show that introducing an appropriate PbBr₂ doping amount can inhibit the formation of undesirable nonphotoactive γ phase, which enhances the crystallization ability, increases the grain size and material band gap of perovskite films, and then suppresses the carrier recombination, reduces the contact resistance, and facilitates the carrier extraction and transport at the interface. This ultimately leads to an improvement in the power conversion efficiency (PCE) and stability of the PSCs. Consequently, the optimized MA_xFA_1–xPbI_3–yBr_y PSCs with 0.05 M PbBr₂ doping achieve an impressive PCE of 17.94%, which is significantly higher than that of the undoped devices (16.69%) and reaches the high level of PSCs with a hybrid chemical vapor deposition (HCVD) method.