A new efficient synthesis of CuO thin films using modified SILAR method

Abstract

Due to its direct band gap and high absorption coefficient, Cupric Oxide (CuO) is widely used as an absorbent material for solar cells, yet most of the available deposition methods are expensive and complex. For this reason, this paper is concerned with the elaboration of CuO thin films using the simple and inexpensive modified successive ionic layer adsorption and reaction method, i.e., modified SILAR method. To that end, glass slide substrates and an aqueous solution of hydrated copper chloride (CuCl $$_{2}$$ ·2H $$_{2}$$ O) complexed with aqueous ammonia (NH $$ _{3} $$ ) (25–28%) were used, then the growth conditions were carefully evaluated to reduce the presence of the remaining phases other than CuO. The elaborated thin films are studied from four perspectives: (1) structural decomposition, (2) morphological decomposition, (3) chemical decomposition and (4) optical properties. It is found that the deposited films are polycrystalline and crystallized in a pure CuO monoclinic structure without any other secondary phase. Raman and X-ray photoelectron spectroscopy confirmed the pure phase obtained and the scanning electron microscopy images showed that the resulting films were dense, smooth and homogeneous. The energy dispersive X-ray spectrum and the elemental mapping scan corroborate the uniform distribution of Cu and O elements on the film surface. Furthermore, UV–visible spectra exhibited a negative correlation between optical transmission and deposition cycles—if the deposition cycles increased, optical transmission decreased similarly the optical band gap. As well as the refractive index and Urbach energy were determined. As a result, the synthesis technique is very simple and low cost, CuO thin films could be appropriate for solar cells applications.