2D hexagonal CuBixGa1−xSe2 nanosheets for a visible light photodetector

Abstract

CuGaSe₂ is in high demand as a promising solar cell material, and the ability to adjust the bandgap is crucial for creating narrow or wide band gap materials. In this study, the bandgap was modified by substituting Ga with Bi, and the resulting effects on the photocurrent response for photodetector applications were investigated. Hexagonal nanosheets of CuBi_xGa_1−xSe₂ (with x values of 0, 0.2, 0.4, 0.6, and 0.8) were produced using microwave synthesis, varying the concentrations of Bi and Ga. The different Bi/Ga ratios led to polycrystalline structures and the inclusion of Bi resulted in the emergence of the Bi₃Se₄ phase. Raman spectroscopy showed shifts in peaks corresponding to different vibrational bonds, indicating structural transformation within the matrix due to compositional changes. Morphological analysis confirmed the 2D hexagonal nanosheet architecture. The oxidation states of the elements were detected from X-ray photoelectron spectroscopy. The optical absorption is reduced with an increment in reflectance over the UV-NIR region and also results in the structural transition inside the matrix by Bi content. This enhanced the energy gap with the reduction in defects and disorder in the material. Such a material has broad absorbance and bandgap over visible and near-infrared regions for potential detectors and solar cells. The broad photoluminescence band emission under 532 nm excitation with reduced intensity is observed in Bi-doped samples. These 2D hexagonal sheets produced good photoconductivity to white light with increased photocurrent, and the photocurrent response over time showed good responsivity and stability. The observed changes in optical and electrical behavior are highly essential for a range of optoelectronic devices, especially for photodetection purposes.