On the effect of thickness of Te Interlayer on output characteristics of CdTe thin-film solar cell

Abstract

Abstract Charge carrier dynamics which governs the output characteristics and performance of solar cells, often depends on the fabrication protocol of these cells. In this study, we have fabricated the FTO/CdS/CdTe/Te/Al thin-film photovoltaic devices using thermal evaporation. We have deposited tellurium as an interlayer between the absorber layer (CdTe) and top-electrode (Al) for a better charge carrier collection. The thickness of this interlayer was varied (10 nm and 30 nm) to observe its effect on the final device output characteristics, and for the same purpose, the fabrication procedure, the thickness of the absorber layer and window layers (CdS) were kept constant of 500 nm and 100 nm respectively. The XRD analysis revealed that the CdS-window layer had a cubic structure while the CdTe existed in both hexagonal and cubic phases. The deposited CdS and CdTe thin-films showed a bandgap of 2.35 eV and 1.5 eV respectively. The device with interlayer thickness of 30 nm device showed a maximum open-circuit voltage (Voc) of 0.40 V and a maximum current of 25 μA whereas for the device with 10 nm thick interlayer shows a Voc of 0.45V and an output current of 6 μA This suggests that introduction of an interlayer enables efficient charge collection and the ability of the charge collection enhances when the thickness of interlayer is increased however, the Voc is marginally different probably due to presence of defects in the 30 nm-thick interlayer cells.