Eects of Post Deposition Treatments on Vacuum Evaporated CdTe Thin Films and CdS=CdTe Heterojunction Devices

Authors: Habibe BAYHAN, Çiğdem ERÇELEBİ

Abstract: $CdTe, CdS$ thin films and $n-CdS/p-CdTe$ heterostructures have been prepared by conventional vacuum evaporation technique. Some post deposition treatments to optimize the device efficiency have been analyzed and the effects of the individual process steps on the material and device properties were investigated. Annealing in air with and without $CdCl_2$-treatment decreased the $CdTe$ resistivity. The $CdCl_2$-dip followed by annealing in air at $300^{\circ}C$ for 5 min improved the grain size and polycrystalline nature of $CdTe$ thin films. Solar efficiency improvements were achieved when heterojunctions were prepared on successively treated (i.e. etched, air annealed, $CdCl_2$-processed) $CdTe$ surfaces. Etching of the $CdTe$ surface with potassium dichromate solution prior to metal contact deposition lead to the formation of low-resistance $Au$ contacts and increase in open circuit voltage and fill factor values.

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