A Redox-Stable Samarium(III) Cation-Engineered Hybrid Perovskite Layer for Highly Efficient and Stable Perovskite Solar Cells

Metal cation doping in hybrid perovskite semiconductors is one of the most effective approaches for tailoring their optoelectronic properties. However, their location-dependent functional mechanisms within the photoactive layer of perovskite solar cells (PSCs) remain poorly understood. Herein, we report that redox-stable samarium cations (Sm3+) enhance the performance of the PSC via partial substitution of lead ions (Pb2+). The optimized concentration of Sm3+ (5%) modulates the crystal quality, defect density, and charge carrier behavior of the perovskite layer. As a result, Sm3+-doped hybrid perovskite-based PSCs exhibited a superior power conversion efficiency (PCE) of 24.66% in contrast to control PSCs. The unencapsulated Sm3+-doped devices resist ≥90% of their initial PCE after 1000 h under 25–30% relative humidity and room temperature in the dark. This work paves the way for a deeper understanding of lanthanide doping in perovskites and enhancing the device performance of PSCs.