120 MeV Ag9+ Ion Irradiation Induced Modification in CuInSe2 Thin Films for Solar Cell Applications

CuInSe₂ is a potential absorber material for thin film solar cell applications due to its direct bandgap and high absorption coefficient. It can be used for both terrestrial and space applications due to its light weight and higher irradiation tolerance among low-cost thin film solar cell absorbers. This paper reports the influence of 120 MeV Ag⁹⁺ swift heavy ion irradiation on the structural and optical properties of CuInSe₂ thin films prepared by pulsed laser deposition. Swift heavy ion irradiation was carried out at room temperature with fluence ranging from 1 × 10¹² to 1 × 10¹³ ions/cm². The x-ray diffraction patterns of the films confirmed the synthesis of a polycrystalline chalcopyrite CuInSe₂ structure with preferential orientation along the (112) plane. The grain size of the films decreased and the peak position shifted toward a lower angle after irradiation. The Raman spectra exhibited a strong peak at 174 cm⁻¹, and the intensity of the peak decreased with the increase in ion fluence. The absorption band edge and optical bandgap of the films were found to be shifted with the varying irradiation fluence. Atomic force microscopy (AFM) studies showed uniform grain growth in non-irradiated film. The average surface roughness of thin film increased with increasing ion fluence. The obtained results showed the influence of the ion beam for tailoring the structural and optical properties of CuInSe₂ films, making it a suitable material for solar cell applications.