In this study, we developed novel composites of degenerately doped copper selenide and polydimethylsiloxane (DDCS/PDMS) that efficiently harness a wide range of solar light for both electricity generation and water purification. The DDCS nanocrystals possess remarkable optical absorption capabilities across the near-infrared (NIR) solar spectrum, leading to enhanced photothermal effects. Within the DDCS/PDMS composite, this results in remarkable light-to-heat conversion, sustaining a consistent surface temperature of 51.5 °C in contrast to the 39.8 °C exhibited by bare PDMS when subjected to standard 1 sun intensity for 3 min, and leveraging its exceptional photothermal characteristics, the composite demonstrated noteworthy thermoelectric power generation, achieving 95 mV, while pristine PDMS only managed 49 mV under 1 sun conditions. Moreover, the DDCS/PDMS foam demonstrated outstanding solar-to-vapor performance, achieving a rate of 1.71 Kg m−2 h−1 with an efficiency of 91.5 % under equivalent sunlight exposure. Remarkably, the versatile DDCS/PDMS foam effectively demonstrated its capability in seawater desalination, achieving an efficiency exceeding 80 % even under the most challenging conditions. This study uncovers the compelling potential of solar-thermal energy utilization and introduces an innovative approach for solar-driven water purification and power generation. By addressing the challenges of sustainable energy and clean water provision, these findings offer a promising avenue forward.