Solar desalination offers an eco-friendly method for producing clean water with minimal carbon emissions by utilizing solar energy. However, the process of solar-vapor generation is highly energy-intensive, resulting in low evaporation rates under natural sunlight. Here, we present La₀.₇Sr₀.₃MnO₃, an oxide perovskite, as a photothermal material capable of efficiently converting solar light into heat. This is achieved by creating intra-band trap states that facilitate heat release through thermalization via non-radiative recombination of photoexcited electrons and holes. A key challenge in solar desalination is ensuring material stability and mitigating salt accumulation. Our specially designed device addresses this by enabling one-directional fluid flow, creating a salt gradient that directs salt accumulation to the edges of the photothermal material, thus minimizing fouling. Combining La₀.₇Sr₀.₃MnO₃ with this innovative design achieves a solar evaporation rate of 3.08 kg m⁻² h⁻¹ under one sun, while also demonstrating effective antifouling in complex environments. This work highlights a practical strategy to enhance solar desalination efficiency and durability through advanced materials and design.