High responsivity and photovoltaic effect based on vertical transport in multilayer α‐In${}_2$Se${}_3$

Herein, device demonstration based on vertical transport in multilayer α‐In${}_2$Se${}_3$ is reported. Photodetectors realized using a metal/α‐In${}_2$Se${}_3$/indium tin oxide (ITO) vertical junction exhibit clear signature of the band edge in spectral responsivity. The wavelength at 680 nm corresponding to an ultrahigh responsivity of 1000 A W${}^{\text{â}\text{ˆ}\text{’}1}$ and a detectivity of >10${}^{13}$ cm Hz${}^{0.5}$ W${}^{\text{â}\text{ˆ}\text{’}1}$ at a bias of 0.5 V. The variation of responsivity and detectivity with optical power density is studied, and a transient response of 20 ms is obtained for the devices (instrument limitation). In addition, an asymmetric barrier height arising out of ITO and Au contacts to a vertical α‐In${}_2$Se${}_3$ junction resulted in a photovoltaic effect with V${}_{OC}$ ≈0.1 V and I${}_{SC}$ ≈0.4 μA under an illumination of 520 nm. (© 2020 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)