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This paper reports simulations of gradual bandgap CIGS absorber and its impact on the characteristics of a solar cell. The bandgap of the CIGS absorber varies linearly and drops from E gmax (at the junction limit) to E gmin (in the vicinity of the rear contact).We introduce an effective absorption coefficient based on this variation. We will demonstrate that this gradual profile contributes to an improvement up to 171 mV of the open circuit voltage V oc of the cell that is linked to the modification of the internal electrical field distribution within the absorber. However, a joint reduction of 1.50 mA/cm 2 of short circuit current density, J sc , is observed. Overall, the conversion efficiency increases from 19.2%, for a uniform bandgap absorber structure, to 24.9% in that case of gradual bandgap. Additionally, we investigate the impact of absorber thickness and temperature on cell characteristics. [ABSTRACT FROM AUTHOR]

This study aims to investigate the different optical properties of the ZnSnN 2 absorber layer such as absorption, reflection and transmission coefficients. The effects of the ZnSnN 2 absorber layer thickness, temperature,and defect density on electrical parameters such as short circuit current density, open circuit voltage, fill factor and efficiency have also been studied in detail. These factors play an important role in the performance of the ZnO/CdS/ZnSnN 2 /Si/Mo structure. The highest efficiency of about 23.32 % is achieved without defects in the ZnSnN 2 absorber layer, under the 1-sun AM1.5 solar spectrum, by applying the flat band condition and considering the strain values of 0.37 % (ZnSnN 2 /Cds) and 7.17 % (ZnSnN 2 /Si). In addition to high efficiency, the ZnSnN 2 has a high absorption coefficient. This device will play a crucial role in optoelectronic applications. This structure is a promising candidate for low cost and high efficiency photovoltaic technology. [ABSTRACT FROM AUTHOR]