Reconfiguration of d-orbital states drives non-radiative energy dissipation in semiconductors

Efficient photothermal conversion relies on the dissipation of energy from photoexcited charge carriers through non-radiative pathways. However, the fundamental electronic structure origins governing such processes in semiconductors remain poorly understood, limiting the rational design of photothermal materials. Here, using TiO2 as a model system, we demonstrate that multi-transition-metal doping provides an effective strategy to simultaneously regulate electronic configurations and spin states, thereby governing carrier relaxation pathways. The incorporation of Fe, Co, and Mn into the TiO2 matrix induces a redistribution of 3d-orbital defect states within the bandgap, giving rise to d–d interband transitions (IBTs), suppression of spin polarization, and accelerated non-radiative recombination. As a result, the optimized FeCoMn–TiO2 exhibits broadband solar absorption and a near-unity photothermal conversion efficiency (97.9%), along with a high solar steam generation rate of 3.82 kg m−2 h−1 (91.2%). These findings establish a direct link between d-orbital electronic structure, spin characteristics, and non-radiative energy dissipation, providing a conceptual framework for designing photothermal semiconductors through electronic state engineering.