Theoretical Insights into Depth-Adaptive Bandgap Engineering Enabling Over-60%-Efficient Perovskite Photovoltaics in Deep-Sea Environments

Underwater photovoltaics have emerged as a promising power supply for marine Internet-of-Things devices and environmental monitoring systems; however, practical deployment remains limited by depth-dependent spectral attenuation, compounded by significant experimental complexity and cost. Here, we develop a comprehensive depth-adaptive design framework for wide-bandgap CsPbI3–xBrx perovskite solar cells (PSCs) based on drift-diffusion device simulations using wx-AMPS. The simulation results reveal that the optimal absorber bandgap increases monotonically with depth, from 1.9–2.15 eV at 2 m (photoelectric conversion efficiencies (PCEs) > 46%) to 2.1–2.25 eV at 20 m (peak PCE ≈ 55.4%) and further to 2.3 eV at 50 m, while the optimal absorber thickness simultaneously decreases from 0.7 to 0.3 μm. Notably, CsPbI0.5Br2.5 (2.2 eV) exhibits exceptional depth adaptability, maintaining a theoretical PCE of 53.07% ± 2.38% over a broad depth range of 10–40 m. For extreme deep-sea conditions (50 m depth), the design further incorporates a wide-bandgap In2O3 electron transport layer together with tailored interfacial buffer layers to simultaneously enhance short-wavelength photon utilization and charge extraction. This synergistic optimization enables a theoretical PCE exceeding 60%. Overall, this work provides a comprehensive theoretical framework and practical design strategy for high-efficiency, depth-aware underwater solar energy harvesting, paving the way for powering autonomous systems in deep-sea environments.