ZrO₂ quantum dots/graphene phototransistors for deep UV detection

Graphical abstract: Electron-hole pairs are generated in the ZrO2 quantum dot film under UV light irradiation, and then holes transfer to graphene layer due to the lower energy levels for holes in graphene, leaving electrons trapped in the ZrO2 QDs, which acted as an additional light tunable gate. The graphene and ZrO2 quantum dots act as the conducting channel and the light absorption layer respectively. - Highlights: • High photo-responsivity and low-cost photo-transistors for deep-UV detection based on graphene decorated with ZrO2 . • Graphene has been used as carrier transport channel and ZrO2 QDs provide strong advantage of deep-UV absorption. • Electron-hole pairs get separated at the interface between graphene and ZrO2 QDs, which leads to the transfer of holes from QDs towards graphene, and the traps of electrons in the ZrO2 QDs that acted as an additional light tunable gate.Electron-hole pairs get separated at the interface between graphene and ZrO2 QDs, which leads to the transfer of holes from QDs towards graphene, and the traps of electrons in the ZrO2 QDs that acted as an additional light tunable gate. - Abstract: ZrO₂ is a promising material for deep-UV detection application, yet the low carrier density and high crystal lattice defects hinder the device performance. Graphene is an attractive material for photoactive and charge transport layers in photodetectors, but the photoresponsivity have been limited by the weak light absorption, no wavelength selectivity. Here, we demonstrate heterostructure phototransistors consist of graphene as the conducting channel, which is covered by a film of ZrO₂ quantum dots as the light absorption layer. Light absorption in the quantum dots layer creates electron-hole pairs. Under the built-in electric field, the electrons are trapped in ZrO₂ acting as an additional light tunable gate, whereas the holes are transferred towards the graphene. The ZnO₂/Graphene heterostructure, with a high photoresponsivity of 22 A W⁻¹ and wavelength selectivity to deep UV wavelength range (220–250 nm) at low operating voltage, is promising to be integrated into solution processed and low-cost optoelectrical devices.