Bandgap engineering for efficient perovskite solar cells under multiple color temperature indoor lighting

Abstract

Perovskite indoor photovoltaics (PIPVs) are emerging as a transformative technology for low-light intensity energy harvesting, owing to their high-power conversion efficiencies (PCEs), low-cost fabrication, solution-processability, and compositionally tunable band gaps. In this work, methylammonium-free Cs_xFA_1−xPb(I_1−yBr_y)₃ perovskite absorbers were compositionally engineered to achieve band gaps of 1.55, 1.72, and 1.88 eV, enabling matching of the spectral photoresponse with indoor lighting. Devices based on a scalable mesoscopic n–i–p architecture were systematically evaluated under white LED illumination across correlated color temperatures (3000–5500 K) and light intensities from 250 to 1000 lux with an active area of 1 cm². The 1.72 eV composition exhibited the most promising performance across different light intensities and colors, achieving PCEs of 35.04% at 1000 lux and 36.6% at 250 lux, with a stable device operation of over 2000 hours. On the other hand, the 1.88 eV band-gap variant reached a peak PCE of 37.4% under 250 lux (5500 K); however, performance trade-offs were observed across different color light LEDs. Our combined experimental and theoretical optical–electrical simulations suggest that decreasing trap-assisted recombination in wide-bandgap compositions may further improve PIPV performance across the different illumination conditions. In contrast, devices with 1.55 eV band gap underperformed in such conditions due to suboptimal spectral overlap and utilization. These findings establish bandgap optimization and device architecture as key design principles for high-efficiency, stable PIPVs, advancing their integration into self-powered electronic systems and innovative indoor environments.