Investigation of the Current-Voltage Characteristics of CdS/CdTe-Based Solar Cells Using Model Calculations
CdTe can be grown as n-type or p-type although the p-type can also be formed by converting n-CdTe to p-CdTe through the well known CdCl2 treatment, which is an important step taken to improve the conversion efficiency of CdTe solar cells. However, the assumption by most researchers is that CdTe is always a p-type material and so can only form a p-n junction with its n-CdS counterpart. This is not always the case as n-n heterojunction + Schottky junction can be formed when an n-CdTe is involved, with group I metals such as Au and Cu as back metal contact. In this work, p-n junction model and Schottky junction model are presented. In order to verify the junction type formed by various CdS/CdTe-based solar cells reported in the literature, current-voltage data of these experimental results are simulated with the junction models using MATLAB programming platform and compared so as to find out the junction model that best describes each experimental result. Diode parameters such as ideality factor, barrier height, and series resistance were adjusted during the simulation. The junction models are found to be in good agreement with some of the experimental results.
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