Interface phonon coupling-boosted photo-thermoelectric response in a SrTiO3/PbSe heterostructure

Abstract

Thermoelectric semiconductors hold significant scientific and technological value, with extensive applications in thermoelectric power generation, infrared detection, and heat management. The thermal radiation absorption of thermoelectric semiconductors is crucial to their thermal-to-electrical conversion efficiency. However, high thermoelectric figure-of-merit (ZT) lead-based chalcogenides (e.g., PbS) exhibit absorption limited to the short-wave infrared range. This limitation arises from their direct interband transition, which lead to significant energy loss in the long-wave radiation region. Herein, we designed a SrTiO3/PbSe heterostructure with interfacial strong longitudinal acoustic phonon interactions. This design extends the response spectrum of PbSe from mid-wave infrared (<4.5 μm) to long-wave infrared (>8 μm) using the long-wave infrared phonon-absorbing material SrTiO3. The SrTiO3/PbSe heterostructure demonstrates high sensitivity to long-wave blackbody radiation (8–14 μm) at room temperature, achieving a blackbody responsivity of 1.62 × 104 V W−1 and a detectivity of 1.75 × 108 cm Hz1/2 W−1. Our work provides a unique physical model to enhance optical-to-electrical conversion efficiency in thermoelectric semiconductors by means of phonon-mediated spectral broadening, with promising applications in long-wave infrared detection and thermoelectric generators.