Hot injection synthesis route has been successfully applied for the preparation of high quality Cu2WSe4 (CWSe) nanosheets in order to determine their optical characterization and device parameters. Several techniques including XRD, SEM, TEM and SAED were used to characterize these nanosheets. These techniques confirmed that Cu2WSe4 nanosheets crystal shapes of synthesized are rectangular and square sheet and the average crystal size is between 20 and 40 nm. The spin coating technique was successfully used to deposit uniform of Cu2WSe4 thin film. Cu2WSe4 thin film has directly transition with a band gap of 1.64 eV. The dispersion of the refractive index is discussed in terms of the single oscillator Wemple–Didomenico (WD) model. The single oscillator energy (E0) and the dispersion energy (Ed) were estimated. Au/Cu2WSe4/n-Si structures was fabricated and its main electrical characteristics described by using current–voltage (I–V) methods. The forward and reverse bias current voltage (I–V) characteristics of Au/Cu2WSe4/n-Si at room temperature were studied to investigate its basic electrical parameters [i.e. saturation current (I0), ideality factor (n), barrier height (Φ B), series (Rs)]. Structural and optical mechanisms were discussed for future applications in optoelectronic devices.