High-efficiency lead-free Cs2SnI3Br3 perovskite solar cells via interface and thermal engineering

Here, we present an integrated optimization strategy for lead-free Cs2SnI3Br3 perovskite solar cells that combines absorber-layer thickness engineering, precise interface band-offset tailoring via electron transport layer/hole transport layer selection, black-phosphorene-based interface passivation, and coupled thermo-electrical degradation modeling. Unlike previous studies focusing on individual device parameters, this comprehensive approach achieves a simulated record power conversion efficiency of 24.7% at 300 K together with quantitatively assessed improvements in thermal and operational stability. A one-dimensional lumped thermal model, self-consistently linked to temperature-dependent SCAPS-1D simulations and an Arrhenius-type degradation law, is used to track the evolution of cell temperature, open-circuit voltage, and efficiency under prolonged thermal stress. We demonstrate for the first time that targeted two-dimensional black phosphorene passivation (5–8 nm) strongly suppresses interfacial recombination and extends the device quantum-efficiency response into the near-infrared region, enabling broader solar-spectrum utilization. Under accelerated thermal-ageing conditions, the initial efficiencies of 24.06%, 24.66%, and 24.7% for unpassivated, 5 nm-BP, and 8 nm-BP devices decrease to about 17.6%, 21.7%, and 23.2%, respectively, confirming that BP passivation significantly slows thermally induced efficiency losses. These findings provide practical, transferable design principles for the scalable fabrication of high-performance, environmentally benign photovoltaic devices, linking interface engineering to thermal robustness and long-term energy yield.