The Development of Technology CdTe and CdS Layers for Thin-Film Solar Cells Creation

Abstract

Under optimization of the cadmium telluride base layers deposited by thermal vacuum evaporation it has been established that the main defects of the structure, namely twins and stacking faults, accompany to the axial texture in CdTe facecentered cubic lattice and to the layerwise film growth. It has been shown that the optimal thickness of the “chloride treated” base layer in the thin film ITO/CdS/CdTe/Cu/Au solar cells (SC) equals 4 $\mu$m. The decreasing of CdTe film thickness leads to the SC efficiency decreasing as a result of the shunting resistance reduction, saturation diode current density and series resistance increasing. The CdTe film thickness growth leads to the SC efficiency decreasing because of the shunting resistance reduction and series resistance increasing. Experimentally approved the possibility of the deposition by close box method of the high-quality from the point of view of their structure CdTe base layers at the substrate temperatures in the range 300 - 450°C. It has been shown that for thin film glass/ITO/CdS/CdTe/Cu/Au SC optimal cadmium sulfide thickness equals 0.4 $\mu$m because of two competitive physical processes, namely, simultaneous variation of the diode saturation current density and the photocurrent density It has been experimentally demonstrated that the maximal efficiency of ITO/CdS/CdTe/Cu/Au SC corresponds to the 0,35 $\mu$m CdCl 2 thickness at “chloride treatment”. In this case both minimal series resistance and lowest diode saturation current density are achieved simultaneously