Towards Ultra Thin and High Efficiency ZnxCd1-xS/CdTe Solar Cell by AMPS 1D

The main motivation of this work was to obtain high efficiency at reduced CdTe absorber layer thickness and replacing ZnxCd1-xS as window layer in conventional CdS/CdTe solar cells. The conventional CdTe baseline case was the starting point of this investigation to analyze ultra thin and high efficiency ZnxCd1-xS/CdTe solar cell for optimal value of x. The initial step of the analysis was to decrease the CdTe absorber layer to the extreme limit of 1 µm and at this thickness the proposed cell has shown satisfactory level of efficiencies. The ultimate step was to insert a suitable back surface field (BSF) with As2Te3 to reduce the back contact barrier height and back surface recombination loss of the ultra thin cell. All the analysis was done using the widely used simulator Analysis of Microelectronic and Photonic Structures (AMPS 1D). The conversion efficiency of 18.02% (Voc = 0.89 V, Jsc = 25.34 mA/cm2, FF = 0.78) without BSF and an efficiency of 20.3% (Voc = 0.93 V, Jsc = 25.97 mA/cm2, FF = 0.825) with As2Te3 BSF were achieved for the proposed cells from 1 µm and 0.6 µm CdTe absorber layer respectively. Moreover, the normalized efficiency of the proposed ultra thin cells linearly decreased with the increasing operating temperature at the gradient of -0.35%/°C, which indicates better stability of the ultra thin cells.

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