Electrochemically synthesized broadband antireflective and hydrophobic GaOOH nanopillars for III-V InGaP/GaAs/Ge triple-junction solar cell applications

We report the efficiency enhancement of III-V InGaP/GaAs/Ge triple-junction (TJ) solar cells using a novel structure, i.e., vertically-oriented gallium oxide hydroxide (GaOOH) nanopillars (NPs), as an antireflection coating. The optical reflectance properties of rhombus-shaped GaOOH NPs, which were synthesized by a simple, low-cost, and large-scalable electrochemical deposition method, were investigated, together with a theoretical analysis using the rigorous coupled-wave analysis method. For the GaOOH NPs, the solar weighted reflectance of similar to 8.5% was obtained over a wide wavelength range of 300-1800 nm and their surfaces exhibited a high water contact angle of similar to 130 degrees ( i.e., hydrophobicity). To simply demonstrate the feasibility of device applications, the GaOOH NPs were incorporated into a test-grown InGaP/GaAs/Ge TJ solar cell structure. For the InGaP/GaAs/Ge TJ solar cell with broadband antireflective GaOOH NPs, the conversion efficiency (eta) of similar to 16.47% was obtained, indicating an increased efficiency by 3.47% compared to the bare solar cell ( i.e.,eta similar to 13%). (C)2014 Optical Society of America