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

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.