Room-temperature photoluminescence characterization of thin-emitter GaAlAs/GaAs and GaAlAs/GaAs/Ge solar cells

Abstract Room-temperature photoluminescence (RT-PL) has been applied to the study of AlGaAs/GaAs and AlGaAs/GaAs/Ge thin-emitter solar cells grown both by metal-organic vapor phase epitaxy and liquid phase epitaxy. It will be shown that: (i) the PL spectrum emitted by the solar cell under the short circuit condition is determined mainly by the emitter radiative contribution; (ii) in the open circuit condition both emitter and base radiative emissions are important as they are produced by injection luminescence; (iii) for solar cells with the same structure (same doping level and layer thickness) the correlation between the PL intensity and the electrical device characteristics (Voc, Isc) can be used to evaluate the presence of recombination centers in the depletion region and junction shunt paths; (iv) for AlGaAs/GaAs/Ge solar cells, interference effects must be taken into account to simulate the experimental PL spectra; and (v) through PL mapping important information can be gained about homogeneity and defect distribution in solar cells grown with different techniques. It will be demonstrated that RT-PL can be used to control different steps of the solar cell processing evidencing its important role as an analysis tool for these devices.