Scalable Production of Light-Sensitive Devices from Liquid-Phase Exfoliated Transition Metal Monochalcogenide Flakes

Abstract

Layered semiconductors of IIIA–VIA group, have attracted considerable attention in (opto)electronic applications thanks to their atomically thin structures and their (opto)electronic properties. Currently, two-dimensional (2D) indium selenide (InSe) and gallium selenide (GaSe) are emerging as promising candidates for the realization of light-driven thin-field effect transistors (FETs) and photodetectors due to their high intrinsic mobility (102 – 103 cm2V−1s−1) and their direct bandgap in an energy range (1.3 – 3.2 eV) suitable for UV, visible and NIR light detection. A requirement for large-scale electronic applications is the development of low-cost, reliable industrial production processes. In this context, it has been recognized that liquid-phase exfoliation (LPE) of InSe and GaSe is a cost-effective and environmentally friendly way to formulate inks for FETs, presenting a significant advantage over conventional methods. In this study, printed InSe and GaSe phototransistors are presented showing high responsivity (13 – 274 AW−1) and fast response velocity (15 – 32 ms). Furthermore, GaSe phototransistors show an on-off current ratio of ~ 103 in the dark, which can be readily achieved without the need for complex design of drain/source contacts or gating techniques. The gate-dependent photoresponse shows that the phototransistors can be modulated by the gate voltage. These results demonstrate that liquid-phase exfoliated InSe and GaSe are valid candidates for low-cost high-performance (opto)electronic devices.