Phase structure stabilization engineering for efficient and stable inverted perovskite solar cells

Abstract

Currently, high-efficiency perovskite solar cells (PSCs) are typically fabricated in an inert atmosphere, as oxygen or humid environments tend to induce the formation of the non-photovoltaically active δ-phase in the FAPbI3 system, leading to severe non-radiative recombination and energy loss, which limits device efficiency and stability. Here, we propose a strategy for the stable regulation of phase structure to achieve high-efficiency and stable inverted PSCs. This study demonstrates that the incorporation of the rare-earth terbium ion Tb3+ can effectively reduce the energy difference between the α- FAPbI3 and δ- FAPbI3 phases, thereby regulating the phase transition behavior of FAPbI3. This effectively lowers the binding energy of the yellow phase, suppressing the formation of the non-photoconductive δ-phase, while the more electronegative halide ion Cl⁻ replaces I⁻ partially. This forms Tb-I and Pb-Cl bonds with stronger bond energies, stabilizing the perovskite lattice structure while passivating Pb2+ and I⁻ vacancy defects within the perovskite. Devices fabricated using this strategy achieved a photoconversion efficiency (PCE) as high as 26.29% without the introduction of an anti-reflection layer. Furthermore, the unencapsulated devices demonstrated exceptional long-term stability; after continuous storage for 10,000 hours in a nitrogen (N2) atmosphere, the devices retained more than 90% of their initial PCE.