Optimization of Chalcogenide CdTe, CZTS and CZTSe Solar Cells PerformancesUsing Cd1-xZnxS Buffer Layer

Cadmium zinc sulfide (Cd1-xZnxS) as a wide-band gap material with x=0.7 was used inthe present work as an alternative buffer material to CdS to improve the efficiency ofZnO/Cd1-xZnxS/CdTe, ZnO/Cd1-xZnxS/CZTS and ZnO/Cd1-xZnxS/CZTSe thin film solar cells. The photovoltaic parameters such as efficiency, open circuit voltage (Voc), short circuit current density (Jsc) and the fill factor (FF) have been computed using one-dimensional simulation programs such as Solar Cell Capacitance Simulator (SCAPS v3.3) and Analysis of Microelectronic and Photonic Structures (AMPS-1D). An improvement in conversion efficiency isnoticed compared to the structure with the CdS buffer layer. It is found that the efficiencies of Cd1-xZnxS/CZTSe and Cd1-xZnxS/CdTeareincreased from 12.61% to 15.35% and from 17.53% to 18.83%, respectively. The simulations were performed for 1 µmthick absorber layers.It is also found that the efficiency rises from 12.53% to 13.23% with Cd1-xZnxS/CZTS structure for CZTS thickness of 2.5 µm. Moreover, the quantum efficiency (QE) characteristics display the maximum value of more than 80% in the visible rangeand the structures presented a slight improvement in the short wavelength. The present study shows that the suggested structures with aCd1-xZnxS buffer layer may improve the efficiency and reduce the amount of Cd, which is a toxic element.