Assessing the effects and impacts of the CdSTe interlayer in the performance of the CdTe-CdS thin film solar cells through simulations

CdTe based solar cells have proved to be the most successful thin film PV solar cells with their full industrial production. However, the needed improvement in output efficiency of these cells is constrained by major issues such the poor understanding of the ternary CdSxTe1-x interlayer, formed at the CdS-CdTe interface. While it is believed to have both beneficial and negative effects on the cell performance, its exact mechanism and extent are not fully explored. In this work, the AMPS-1D software was used to model this interlayer, using several of its variables such as thickness, bandgap as well as the thickness of the bounding CdS layer. Results show that the interlayer thickness reduces cell performance, through Jsc, Voc, FF and J-V curves, with best efficiencies of 17.892% (Jsc=27.043mA/cm3, Voc=0.871V, FF=0.8) obtained at zero thickness, falling down by nearly 20% at CdSxT1-x thickness of 100nm. As the bandgap is varied, maximum cell performance of 17.85% (Jsc=27.76, Voc=0.91V and FF=0.81) was found at 1.7eV. Similarly, increasing CdS thickness also reduced cell performance, by reducing the quantum efficiency. The results indicate that if the CdSxTe1-x layer has a thickness of up to 100nm, and a bandgap of around 1.7eV, then cell efficiencies of around 18% were feasible even for ultra-thin CdTe layers of 1μm.