Polarity‐Reversible Photoresponse–Driven Autonomous Wavelength Discrimination in Quantum Dot–Tellurium Thin‐Film Photodetectors via Engineered Energy‐Band Alignment

A self‐judging photodetector (PD) that autonomously distinguishes wavelengths is realized through photon–charge carrier interactions with controlled gain effects, enabled by engineered energy‐band alignment and charge‐transport modulation. This hybrid PD integrates n‐type quantum dots (QDs), p‐type QDs, and a centrally located narrow‐bandgap p‐type Te thin film. Based on the bandgap characteristics and charge‐transport behavior of each semiconductor, the device implements a dual‐response mechanism. Upon illumination, distinct charge‐transfer dynamics between the QDs and Te thin film result in wavelength‐dependent photoresponses. In particular, a negative photocurrent is observed under visible light, while a positive photocurrent is observed under infrared illumination. This dual‐mode response enables the autonomous discrimination of optical signals within a single‐device architecture, eliminating the need for external optical filters or complex circuit‐level processing. The strategy presented in this study paves the way for advanced sensing applications that require both spectral selectivity and material versatility.