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 CsPbI 3– x Br x 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, CsPbI 0.5 Br 2.5 (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 In 2 O 3 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.