CHARACTERIZATION OF 1.0 EV GaInNAsSb SOLAR CELLS FOR MULTIJUNCTION APPLICATIONS AND THE EFFECT OF ANNEALING

摘要

This work focuses on the characterization of 1.0 eV GalnNAsSb solar cells for application to the high efficiency multijunction solar cells. In the multijunction scheme such as GaInP / GaAs / GaInNAsSb and GaInP / GaAs / GaInNAsSb / Ge, the thickness of the GaInNAsSb absorber should be thicker than 2 μm to ensure optimal amount of current generation matched to those of the other subcells. In this study, 1.0 eV GaInNAsSb thin films and solar cells grown by molecular beam epitaxy were investigated. For the purpose of improving the material quality, post-growth annealing was applied. After the annealing, photoluminescence efficiency together with the carrier recombination rate was found improved. The spectral responses in external quantum efficiency measurements at wavelengths longer than 870 nm increased with increasing the GaInNAsSb thicknesses, and reaches close to 90% for the 2.0 nm-thick device. In order to characterize further the multijunction solar cell properties, the 2.0 μm device was mechanically connected with a GaInP / GaAs dual-junction cell in series. The light Ⅰ-Ⅴ measurement was carried out and 25.9% of efficiency was achieved for the mechanically connected triple-junction structure under the AM-1.5 spectrum.