Highly-transparent ZnO:Ga through rapid thermal annealing for low-bandgap solar cell application

Textured Ga doped ZnO (GZO) films showing strong light trapping ability were prepared at room temperature. Rapid thermal annealing of the textured-GZO films at elevated temperatures was found to be effective to significantly improve their optical transmission without deteriorating the film conductivity. By applying the annealed GZO films to the microcrystalline Si_1-xGe_x (x=0.1) single junction solar cells, an obvious enhancement in the spectral response is achieved. The resulted rather high short-circuit current density (>25.5 mA/cm²) for ~1.1 ¿m absorber layer together with the unaffected open-circuit voltage and fill factor leads to an state-of-art conversion efficiency of 8.2 %.