Sensitive Thermography via Sensing Visible Photons Detected from the Manipulation of the Trap State in MAPbX₃

Sensitive thermometry or thermography by responding to blackbody radiation is urgently desired in the intelligent information life, including scientific research, medical diagnosis, remote sensing, defense, etc. Even though thermography techniques based on infrared sensing have undergone unprecedented development, the poor compatibility with common optical components and the high diffraction limit impose an impediment to their integration into the established photonic integrated circuit or the realization of high-spatial-resolution and high-thermal-resolution imaging. In this work, we present a sensitive temperature-dependent visible photon detection in Bi-doped MAPbX₃ (X = Cl, Br, and I) and employ it for uncooled thermography. Systematic measurements reveal that the Bi dopant introduces trap states in MAPbX₃, thermal energy facilitates the carriers jumping from trap states to the conduction band, while the vacancies of trap states ensure the sequential absorption of visible photons with energy less than the band gap. Subsequently, the change of response toward the visible photon is applied to construct the thermograph, and it possesses a specific sensitivity of 2.11% K^-1 along temperature variation. As a result, our thermograph presents a temperature resolution of 0.21 nA K^-1, a high responsivity of 2.06 mA W^-1, and a high detectivity of 2.08 × 10⁹ Jones at room temperature. Furthermore, remote thermal imaging is successfully achieved with our thermograph.