Designing of novel efficient photoactive ternary Zn1-xCu2xSe thin film materials via hydrothermal route: Photoelectrochemical (PEC) cell study

Herein, facile hydrothermal route was directly employed to synthesize photoactive copper doped zinc selenide (Zn1-xCu2xSe) thin films as function of copper ion concentration. The effect of Cu ion concentration on optical, morphological, structural, compositional and photoelectrochemical properties of Zn1-xCu2xSe thin films have been Investigated. Optical absorption elucidations revealed that, Zn1-xCu2xSe thin films shows direct allowed type of electronic transition with decrease in band gap energy from 2.45 eV to 2.09 eV with varying in Cu ion concentration respectively. A structural study of films confirms the generation of cubic zinc blende crystal structure with crystallite size in the range of 82 nm–58 nm. Decrease in defect level of synthesized material was explored by photoluminescence spectra. Alteration in surface morphology was observed from nanosphere to well grown nanoflakes. High resolution transmission electron microscopy (HR-TEM) and selected area electron diffraction (SAED) study reveals that formation of nanocrystalline Zn1-xCu2xSe thin film. X-ray photoelectron spectroscopy (XPS) analysis confirms the existence of Cu+, Zn2+ and Se2− elements in deposited Zn1-xCu2xSe thin film. The detailed electron impedance spectroscopy (EIS) studies were carried out and it is well support to the photoelectrochemical (PEC) performance of Zn1-xCu2xSe photoanode. From J-V measurements, Cu rich film photoanode shows better PEC performance with best photoconversion efficiency (η) 1.65% for sample CZS5.