Ultrathin Niobium‐Doped Indium Oxide Active Layer Enables High‐Performance Phototransistors for Driving Quantum‐Dot Light‐Emitting Diodes

Abstract Active materials play a crucial role in the performance of phototransistors. However, the discovery of a novel and versatile active material is a big challenge. For the first time, phototransistors with ultrathin niobium‐doped indium oxide (InNbO) active layer are fabricated. The InNbO phototransistors without additional light‐absorbing layers exhibit the performance with a high average mobility of 22.86 cm 2 V −1 s −1 , a turn‐on voltage of −0.75 V, a low sub threshold swing of 0.18 V/decade, and a high on/off current ratio of 5.74 × 10 8 . Detailed studies show that Nb is the key to suppress the free carrier generation due to the strong bonding strength of Nb─O. In addition, the InNbO phototransistors exhibit a very broad spectral responsivity with a photocurrent of 4.72 × 10 −4 A, a photosensitivity of 1.69 × 10 8 , and a high detectivity of 3.33 × 10 13 Jones under violet (405 nm) light illumination, which is significantly higher than that of the IGZO phototransistors. Furthermore, an active‐matrix quantum‐dot light‐emitting diode pixel circuit based on InNbO phototransistors is demonstrated. The findings not only indicate that InNbO is a new active material for phototransistors, but also suggest that InNbO‐based phototransistors have a great potential for the next‐generation interactive display technology.