Relationship between Optical and Thermoelectric Properties of Er and Nb Doped SrTiO₃ Materials

SrTiO3 exhibits promising potential in both thermoelectric and optical properties. However, research on these two properties has consistently been carried out in two relatively independent fields. In this work, the regulatory mechanisms of thermoelectric and optical properties were proposed based on photon-excited electron–phonon interactions. Er doping can enhance the photon absorption of SrTiO3 by introducing impurity energy levels, thereby promoting photoexcited electron generation. The introduction of oxygen vacancies (Vo) enhances the interaction between excited electrons and phonons through defect levels, facilitating the conversion of photon energy into thermal energy and subsequently into electrical energy. Additionally, Er–Nb codoping with Vo synergistically optimizes thermoelectric properties, thereby laying a foundation for the regulation of photothermoelectric properties. As a result, significant photothermoelectric conversion was obtained in the Sr0.85Er0.15Ti0.9Nb0.1O3 (Vo) sample. A maximum ZT value of 0.32 at 1073 K was achieved in this sample, representing a 60% improvement over previously reported Nb-doped SrTiO3 samples. The electrical output power of the Sr0.85Er0.15Ti0.9Nb0.1O3 (Vo) sample reaches 3.85 μW under portable 980 nm laser excitation at 260 mW incident power. These findings provide valuable insights into the conversion of light energy to electrical energy in highly absorptive SrTiO3-based thermoelectric materials.