V2O5 nanoflakes for broad-spectral-response self-powered photodetectors with a high on/off ratio and high detectivity

Abstract

In this study, V2O5 nanoflakes (NFs) was coated on Si substrate by DC sputtering to obtain V2O5 NFs/n-Si heterojunction. To utilize V2O5 NFs as a broadband photodetector, absorbance spectra were studied using UV−Vis−near-IR spectroscopy. Cut-off wavelength was 530 nm. Furthermore, energy dispersive x-ray, x-ray diffraction (XRD), x-ray photoelectron spectroscopy (XPS) and scanning electron microscope analyses of V2O5 NFs were achieved. The V2O5 NFs/n-Si device gave a very high rectifying ratio of 1.18 × 104 in the dark and at zero bias, it has self-powered mode and an on/off ratio of 1.29 × 106. Optical analyses of the V2O5 NFs/n-Si heterojunction device were studied in detail under UV (365, 395 nm) and IR (850 nm) illumination as well as visible light with varying light intensities. Analysis of experimental studies showed that the device has a high photoresponse under all illuminations. For optical analysis based on I–V measurements, responsivity, detectivity, on/off ratio, external quantum efficiency (EQE), normalized photocurrent-dark-current ratio and noise-equivalent power (NEP) analyses were achieved. The maximum values of responsivity from measurements under visible, UV (395 nm) and IR illumination (850 nm) were 104, 882 and 850 mA W−1 for −2.0 V, respectively. Detectivity values are maximized at V = 0 V and are 6.84 × 1011, 7.87 × 1012 and 6.87 × 1012Jones for the same illuminations respectively. With increasing intensity, the rectification ratio and NEP decreased while the other parameters generally increased. The increase in performance at increasing visible intensity was attributed to the increase in photogenerated carrier density at high intensities, and the high performance in the UV region was attributed to the high light absorption of V2O5 NFs in the UV region.