Solution-Processed Low-Voltage-Driven Phototransistors Using Colloidal ZnSnO₃ Nanocrystal

Colloidal zinc tin oxide (ZnSnO₃) nanocrystal (NC), an oxide perovskite-type semiconducting material for optoelectronic applications, have been used as semiconductor channel of a low-operating-voltage thin-film transistor (TFT) that has been fabricated by using a solution-processed ionic gate dielectric of LiInSnO₄, offer high areal capacitance due to its ionic polarization. This scalable ZnSnO₃ (ZTO) NCs was synthesized via a unique reduction method that produces a highly crystalline and pure phase of NCs. The device exhibits a carrier mobility of 1.45 cm²/V.s with on/off ratio of 10³ under 3 V operating voltage, showing a high photosensitivity both under UV and blue light. The photosensitivity and responsivity of the device under blue illumination are 16.4 (at V_G = -1.40 V) and 1.11 A/W (at V_G = 0.2 V), respectively, whereas under UV illumination these values are 136.9 (at V_G = -1.40 V) and 2.74 A/W (at V_G = 0.2 V), respectively. Besides, photocurrent spectra over the range of wavelength have been investigated through external quantum efficiency (EQE) study, indicating UV/Blue photosensitivity of this TFT with larger UV sensitivity. The higher photosensitivity and responsivity under UV illumination of the device originated due to the wide bandgap nature of the ZTO NCs.