Effect of tunnel junction grown at different growth rates on the optical properties and improved efficiency of InGaP/GaAs double-junction solar cells

초록

The optical properties of InGaP/GaAs double -junction solar cells (DJSCs) grown by metalorganic chemical vapor deposition were investigated using temperature- and excitation power -dependent photo- luminescence (PL) measurements. The InGaP/GaAs DJSC samples studied were the same structures; however, the corresponding tunnel junctions were grown at different growth rates (1.0 and 1.5 ?/s). The PL spectrum measured at 10 K for both samples exhibited a strong main peak at -1.97 eV with a weak shoulder peak at -1.94 eV, which could be attributed to the emissions of disordered and ordered InGaP, respectively. A PL peak located at -1.91 eV was observed under a low excitation power, originating from the donor -acceptor pair (DAP) transition. With the increase in the temperature, the emission related to the DAP of the sample grown at a growth rate of 1.0 ?/s was found to be less dominant compared with the sample grown at a growth rate of 1.5 ?/s. The power -conversion ef ficiency of the sample grown at a growth rate of 1.0 ?/s was improved compared to that of the sample grown at a growth rate of 1.5 ?/s, owing to fewer defect states. Our results help understand the luminescence properties of InGaP/GaAs DJSCs, which could be a crucial factor in fabricating high -ef ficiency solar cells.

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