Synthesis of ZnO Quantum Dots and Their Applications in UV-Sensitive Low-Voltage Phototransistors

ZnO quantum dots have been synthesized through a low-cost solution process with less complexity. The solution-processed quantum dots (QDs) demonstrate excellent stability and dispersion with an average crystallite size of ∼4.1 nm, which has been determined through the transmission electron microscopy and X-ray diffraction pattern. Furthermore, these ZnO QDs have also been utilized as a semiconductor channel in a solution-processed low-voltage (≤2 V) thin-film transistor (TFT) where ion-conducting LiInSnO4 thin film has been used as a gate dielectric. The fabricated ZnO QD-based TFT showcases saturation mobility (μsat), on/off ratio, and a subthreshold swing (SS) of 0.6 cm2/V sec, 104, and 166 mV/decade under dark conditions. Besides, using asymmetric work function source and drain electrodes, the on/off ratio and SS of the devices have been improved that effectively improves the UV sensitivity of the device. Under 1 W m–2 UV illumination, this asymmetric source-drain electrode TFT exhibits impressive UV photosensitivity with an external quantum efficiency of ∼25% which is comparably high for an UV phototransistor device.