High efficiency InGaP solar cells for InGaP/GaAs tandem cell application

In this paper, high conversion efficiency single junction InGaP solar cells with n-p-p/sup +/ structure are presented and their application to InGaP/GaAs monolithic tandem cells is discussed. In the InGaP cells, a best conversion efficiency of 18.48% was achieved by introducing the p/sup +/ back surface field (BSF) layer with a high carrier concentration of 2/spl times/10/sup 18/ cm/sup -3/, which improved both short circuit current (Isc) and open circuit voltage (Voc). However, in the case of InGaP/GaAs tandem cells, a decrease in carrier concentration of the InGaP BSF layer, which was caused by the diffusion of Zn, was found to reduce the Isc and Voc of the tandem cell. The reduction in the carrier concentration was suppressed by using a thicker BSF layer of 0.5 /spl mu/m, which reduced the current density in the GaAs bottom cell. An InGaP/GaAs tandem cell with 27.3% efficiency and a high Voc of 2.418 V was obtained.