An Optoelectronic Thermometer Based on Microscale Infrared-to-Visible Conversion Devices

Thermometric detectors are crucial across environmental and biomedical applications. Optical thermometry using photon upconversion offers low autofluorescence and high tissue penetration, advantageous for temperature monitoring. This work presents an optoelectronic thermometer that converts infrared to visible light using integrated light-receiving and emitting devices. Thin-film, microscale devices show temperature-dependent emission with 1.5% °C⁻¹ intensity change and 0.18 nm °C⁻¹ spectral shift. The sensing mechanism arises from temperature-dependent semiconductor band structures and circuit operating conditions. Patterned device arrays enable spatial temperature mapping. Integrated fiber-optic sensors demonstrate real-time thermal detection in vitro (human exhalation) and in vivo (deep brain of animals).