Zn2+ ion doping for structural modulation of lead-free Sn-based perovskite solar cells

Sn-based perovskites have intrinsic defects, such as Sn vacancies, oxidised components (Sn4+), and local lattice strain in the perovskite crystalline structure. In this study, Zn metal powder (Zn-0) was introduced to reduce Sn oxidation in the solution step based on the redox potential difference. Additionally, Zn2+ was introduced in the perovskite precursor, which decreased the intrinsic defects and lattice strain of the perovskite films. The diffusion length, particularly that of the hole, increased with a reduction in the lattice strain, and Zn doping led to interfacial energy-level alignment of the perovskite and hole-transporting layers. The reduced lattice strain decreased the defect density and charge carrier recombination of perovskite devices. The power conversion efficiency of the Zn-doped Sn-based perovskite solar cell was improved to 11.39% compared to the 8.56% of the reference device.