GaAs nanopillar-array solar cells employing in situ surface passivation

• Published in: Nature communications Vol. 4; no. 1; p. 1497
• Main Authors: Mariani, Giacomo, Scofield, Adam C., Hung, Chung-Hong, Huffaker, Diana L.
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 19.02.2013; Nature Publishing Group; Nature Pub. Group
• Subjects: 639/301/299/946; 639/766/25; 639/925/357; Arrays; Electrons; Humanities and Social Sciences; Indium tin oxides; Light; multidisciplinary; Nanowires; Science; Science (multidisciplinary); Simulation; Los Angeles California; United States > US; California
• ISSN: 2041-1723
• DOI: 10.1038/ncomms2509

Arrays of III–V direct-bandgap semiconductor nanopillars represent promising photovoltaic candidates due to their inherent high optical absorption coefficients and minimized reflection arising from light trapping, efficient charge collection in the radial direction and the ability to synthesize them on low-cost platforms. However, the increased surface area results in surface states that hamper the power conversion efficiency. Here, we report the first demonstration of GaAs nanopillar-array photovoltaics employing epitaxial passivation with air mass 1.5 global power conversion efficiencies of 6.63%. High-bandgap epitaxial InGaP shells are grown in situ and cap the radial p–n junctions to alleviate surface-state effects. Under light, the photovoltaic devices exhibit open-circuit voltages of 0.44 V, short-circuit current densities of 24.3 mA cm −2 and fill factors of 62% with high external quantum efficiencies >70% across the spectral regime of interest. A novel titanium/indium tin oxide annealed alloy is exploited as transparent ohmic anode. Arrays of III–V semiconductor nanopillars are promising photovoltaic materials due to their favourable optical properties, however, they show low power conversion efficiencies. Mariani et al . fabricate a GaAs nanopillar solar cell achieving an efficiency of 6.63% owing to surface passivation.