Cycle-Crafted Superlattices: Exploring SILAR-Induced Enhancements in CdSe/CuSe Thin Films for Solar Applications

Abstract: Semiconductor superlattice thin films of CdSe/CuSe were successfully deposited on microscopic glass substrates using SILAR deposition technique. Three SILAR cycles were optimized and the films were subjected for SEM, EDX, UV-Vis and XRD analysis prior to annealing at 423 K for 60 minutes to determine their properties for photovoltaic applications. The SEM image of the CdSe/CuSe superlattice thin film shows the surface contained agglomerated mass of interconnected spherical-like nanoparticles of different sizes. The result of the EDX analysis indicated that more of the Cu-Se atoms are deposited compared to Cd-Se atoms. The optical properties of the films showed that the absorbance and extinction coefficient of the films increased with increase in the SILAR cycles. The film deposited after 10 cycles has the highest absorbance value in the range of 0.75–0.45 in the VIS region and 0.45-0.50 in the NIR, while the film deposited at 2 cycles has lowest value of 0.20–0.10 in the VIS and 0.10 in the NIR region. The bandgap energy was found to decrease as the number of SILAR cycles increased and values obtained are 2.00 eV, 1.95 eV and 1.90 eV for the films deposited at 2, 6 and 10 cycles respectively. These bandgap values are in the range suitable for thin film solar cell and many other optoelectronic applications. Structural analysis revealed that films subjected to a higher number of SILAR cycles exhibited enhanced crystallinity. As the number of SILAR cycles increased, the average crystallite size of the CdSe/CuSe films grew larger. Simultaneously, the dislocation density and micro-strain within the films decreased progressively with the increase in the number of cycles from 6 to 10.

Keywords: cadmium selenide, copper selenide, SILAR, bandgap, superlattice, optoelectronics, solar cells