Multijunction or tandem solar cells can split the solar spectrum over several subcells with different bandgaps to transform the sunlight into electricity more effectively than single-junction solar cells. The monolithic tandem design of third generation silicon solar energy materials is auspicious for photovoltaics. In this paper, the Simulation-based studies of copper zinc tin sulfide/Silicon (CZTS/Si) tandem cells based on CZTS as an upper subcell and silicon as a lower subcell absorber layer have been performed using SCAPS-1D. This study aims to evaluate the CZTS tandem cells' performance based on the fact that both subcells are simulated to produce the best efficiency recorded at its bandgap. The Simulation and optimization of the single junction CZTS and Si solar cells were initially performed to fit the state-of-art records efficiency of 11.65% and 18.7%, respectively. Further, both the upper and lower cell has evaluated at different thicknesses for tandem configuration after validation. Also, to obtain the current matching condition for tandem structure, the upper subcell's performance is investigated at different thickness ranges from 0.1 µm -1 µm while keeping the lower subcell thickness at 80µm. Thus, at optimized upper absorber thickness of 0.191 µm and lower subcell 80 µm at transmitted spectrum the current matching condition obtained and gave an efficiency of 10.6% and 11.9%, respectively. The maximum efficiency of ~ 23 is obtained for tandem design with enhancing open circuit voltage 1.4 V.

Ion beam-induced luminescence (IBIL) is a versatile technique used to elucidate the chemical bond’s nature and analyze the defects study and impurities present in the material. In this study, IBIL spectra of phosphorus-irradiated sapphire has been analyzed under 2 MeV proton beam as a function of ion dose ranging from 1 × 1014 to 10 × 1014 ions/cm2 at room temperature in the wavelength range of 200–1,000 nm. The IBIL spectrum shows three kinds of luminescence features. The bands centered at 419 nm as F center and 330 nm as F+ center are associated with oxygen vacancies. The third kind of luminescence feature located at 704 nm is related to chromium impurities present in the crystal. The luminescence spectrum of the phosphorus-irradiated sapphire has been correlated with the spectrum obtained from pristine sapphire. The finding indicates that the intensity of defects due to phosphorus irradiation is reduced. As the proton ion fluence increases, the F and F+ center luminescence intensity eventually varies; it turns out that in phosphorus-irradiated sapphire, single crystal defects were reduced and the optical quality was improved.