A Defect-Engineered Vacuum Evaporation Strategy for High-Efficiency Indoor Perovskite Mini Solar Modules

Fully vacuum-evaporated perovskite solar cells (PSCs) offer a solvent-free, scalable platform for indoor photovoltaics, yet performance is often limited by incomplete phase conversion and high defect densities. Here, we report a sequential vacuum-evaporation strategy that enables the formation of high-quality perovskite absorbers specifically optimized for low-intensity indoor light harvesting. By co-evaporating PbI₂ with a controlled fraction of PbCl₂, the dense stacking characteristic of thermally deposited PbI₂ is effectively disrupted, promoting homogeneous organic-inorganic interdiffusion and near-complete perovskite phase conversion. Additionally, a thin CsI interlayer introduced prior to thermal annealing stabilizes the photoactive phase and suppresses defect formation at both the bulk and interfacial levels. Consequently, the optimized fully evaporated PSCs deliver record indoor power conversion efficiencies of 41.60% at 900 lux and 41.22% at 300 lux under TL84 illumination. Transient photovoltage and photocurrent analyses reveal prolonged carrier lifetimes and accelerated charge extraction, indicative of substantially reduced nonradiative recombination. Importantly, the devices exhibit markedly enhanced operational stability and enable a perovskite mini module (3.9 cm²), achieving over 38% efficiency at 900 lux under indoor lighting. Collectively, this work establishes a practical and industrially compatible pathway toward high-performance, scalable, fully evaporated perovskite photovoltaics, advancing their deployment in next-generation self-powered indoor electronic systems.