Characterization and Quantitative Analysis of Ultra-thin GaAs Single-Junction Solar Cells with Reflective Back Scattering

This paper studies the impacts of the non-ideal reflective back scattering, non-radiative recombination, and series resistance on the device performance of ultra-thin GaAs single-junction solar cells. The reflectivity of the textured AlInP/Au interface is calculated by averaging the angular reflectivity against the Lambertian distribution, the value of which is 95% at the GaAs absorption edge. The impact of nonideal scattering on short-circuit current density (J(sc)) and external quantum efficiency (EQE) is investigated using Phong's distribution and a Phong exponent m of similar to 12 is determined by fitting both simulated J(sc) and EQE to their experimental values. The measured open-circuit voltage (V-oc) is lower than the best achievable value, and the difference is attributed to the nonradiative recombination in the device. Fitting of the measured V-oc gives a lifetime of similar to 130 ns. The impact of series resistance on fill factor is also studied using the single diode equivalent circuit model and the specific series resistivity of the device is determined to be similar to 1.2 Omega.cm(2).