2D hexagonal CuGaSe2 nanosheets by a microwave assisted synthesis method: photoresponse and optical study for optoelectronic applications

Abstract

CuGaSe₂, a ternary chalcopyrite, has recently garnered attention due to its potential in various optoelectronic and photonic devices. In this current study, 2D CuGaSe₂ hexagonal nanosheets were synthesized using a simple microwave-assisted method with varying irradiation times from 3 min to 20 min. The variation in microwave irradiation confirmed its polycrystalline nature, revealing multiple binary phases of CuSe, Cu₂Se, and Ga₂Se₃ with differing intensities. Changes in the diffraction pattern along with Raman vibrational band intensities indicate structural rearrangements within the system over time variation. Suitable 2D hexagonal nanosheets were observed from morphological studies with slight variations in the sheet thickness. Increasing irradiation time led to the introduction of intermediate levels within the band gap, which red-shifted the optical absorption edge. Such variations over time tend to reduce the optical band gap, introducing more disorder and defects inside the system. Broad reflectance across the visible and NIR spectrum and a reduced band gap make it promising for solar cell applications. The elemental composition and corresponding oxidation state have been confirmed by using different surface chemical analyses. The photocurrent response exhibited an ohmic nature, with slight improvement with irradiation time. The photo-resistance decreased with longer irradiation, possibly due to an increase in acceptor state concentration, boosting current density and reducing resistance at room temperature. This behavior is advantageous for photoresponse applications.