Colloidal Quantum Wells Enable Phototransistors with Enhanced Visible Light Detection

ABSTRACT InGaZnO (IGZO) phototransistors have largely attracted research attention due to their excellent electrical properties. However, the wide bandgap (>3.0 eV) of IGZO phototransistors intrinsically limits their spectral response to UV wavelengths, hindering their applicability in visible‐light optoelectronics. We report integrating colloidal quantum wells (CQWs, spin‐coated at room temperature in ambient air) to extend the spectral sensitivity of IGZO phototransistors into the visible range. The resulting CQW/IGZO heterojunction phototransistor exhibits a six‐order‐of‐magnitude enhancement in specific detectivity ( D * = 1 × 10 11 Jones at 660 nm) across the visible spectrum (405–660 nm), while retaining excellent electrical performance, including a maximum mobility of 13.38 cm 2 V −1 s −1 and an on/off current ratio of 1.53 × 10 9 . Energy‐band engineering at the CQW/IGZO interface, with a conduction band offset (Δ𝐸 𝑐 = 0.15 eV), facilitates efficient charge separation and promotes electron injection into the IGZO channel. Gate‐modulation further enables the device to drive quantum‐dot light‐emitting diodes, underscoring its potential in adaptive sensing and integrated optoelectronics. This work demonstrates the integration of CQWs in thin‐film transistors as a scalable and cost‐effective strategy to broaden the optoelectronic functionality of wide‐bandgap semiconductors.