Processing Insulating CaTiO₃ into a High-performance Photothermoelectric Material

Photothermoelectric (PTE) detectors have attracted extensive attention due to the advantages of no external bias, negligible 1/f noise, and low fabrication cost for arrayed and miniaturized devices, and they circumvent the bandgap limitation of traditional photon detectors. However, the practical application of current mainstream PTE materials remains severely hindered by their poor high-temperature stability, especially in harsh scenarios including high-temperature monitoring and industrial waste-heat detection. In this work, CaTiO₃ is selected as the PTE material owing to its outstanding high-temperature stability, excellent chemical stability, non-toxicity, and low cost. Nevertheless, intrinsic insulating CaTiO₃ possesses neither efficient optical absorption nor favorable thermoelectric properties. Herein, abundant oxygen vacancies are introduced to endow CaTiO₃ with broad-spectrum optical absorption via the formation of defect energy levels within the bandgap. Meanwhile, La doping was employed to improve its thermoelectric performance. As a result, the La_0.2Ca_0.8TiO₃ sample achieves a responsivity of ≈300 mA W^-1 and a noise level below 5 × 10^-9 W Hz^-1/2 across a broad spectral range when only intrinsic resistance is considered. It well meets the application needs of harsh civilian environments with no strict requirement for response speed. This work offers a feasible strategy for developing high-performance PTE detectors applicable to high-temperature and harsh working conditions.