Giant Colloidal Quantum Dot/α-Ga₂O₃ Heterojunction for High Performance UV–Vis–IR Broadband Photodetector

Broadband optoelectronics, which extend from the UV to IR regions, are crucial for imaging, autonomous driving, and object recognition. In particular, photon detection efficiency relies significantly on semiconductor properties, such as absorption coefficients and electron-hole pair generation rate, which can be optimized by designing a suitable p-n junction. In this study, we devise giant PbS colloidal quantum dots (G-PbS CQDs) that exhibit high absorption coefficients and broadband absorption. To leverage these exceptional optical properties, we combine G-PbS CQDs with an ultrawide-bandgap semiconductor, α-Ga₂O₃, and create an efficient G-PbS CQD/α-Ga₂O₃ heterojunction photodetector that exhibits high performance across the UVC-vis-NIR spectrum range. The resultant heterojunction facilitates efficient electron-hole pair separation at the G-PbS CQD/α-Ga₂O₃ heterojunction. Furthermore, we utilize transparent graphene electrodes to overcome the limitations of conventional transistor-type device structures and the substantial optical losses induced by opaque metal electrodes. This strategy maximizes the light-collection area and results in an approximately 3-orders of magnitude higher responsivity (55.5 A/W) and specific detectivity (1.66 × 10¹³ Jones) compared to devices with opaque metal electrodes.