Optoelectronic, photocurrent sensitivity and photocatalytic dye degradation behaviour of spray deposited Cr doped SnO2 thin films

Abstract

Undoped and SnO2:Cr doped thin films (Cr: 0.25, 0.50, 0.75 and 1 wt%) were deposited by economically home-made spray pyrolysis method. The characteristic behaviour of the deposited films was studied by X-ray diffraction (XRD), Scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), Photoluminescence (PL), Ultraviolet–visible (UV–vis.) spectroscopy, Current-Voltage (I–V) and photocatalytic studies. The XRD analysis confirms the tetragonal rutile structure of SnO2 with predominant orientation along the (2 1 1) plane and the decrease in crystallite size from 48 to 30 nm by Cr-doping. The EDAX and XPS studies reveal the elements and its chemical state of Sn, O and Cr. The SnO2:Cr thin films exhibit an 85% average optical transmittance in the visible region of the electromagnetic spectrum. The SEM micrographs clearly show the well-defined grains with boundaries, and it is evident that grain size drastically reduces from 155 nm to 48 nm as a function of Cr-doping. Photoluminescence analysis confirms the defect-related emission (360 nm, 440 and 490 nm). The photocatalytic activity of all thin films is assessed using malachite green (MG) dye under UV light irradiation. 0.75 wt% Cr-doped SnO2 film shows improved photocatalytic performance (60.37%) than undoped thin film (32.03%). The I–V characteristics of undoped and SnO2:Cr thin films are performed in visible light, showing photo-linear response behaviour. The highest figure of merit (FOM) obtained for SnO2:Cr (0.75 wt%) thin film is 7.07 × 10−6 Ω−1. The obtained values of the FOM and photocatalytic performance are discussed in the context of the suitability of these materials for transparent and conducting window materials in solar cells and photocatalytic degradation applications.