Boosting Solar Cell Photovoltage via Nanophotonic Engineering

• Published in: Nano letters Vol. 16; no. 10; pp. 6467 - 6471
• Main Authors: Cui, Y, van Dam, D, Mann, S. A, van Hoof, N. J. J, van Veldhoven, P. J, Garnett, E. C, Bakkers, E. P. A. M, Haverkort, J. E. M
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 12.10.2016
• Subjects: Nanophotonics; photovoltage; open circuit voltage; nanowires; photovoltaics
• ISSN: 1530-6984; 1530-6992
• DOI: 10.1021/acs.nanolett.6b02971

Approaching the theoretically limiting open circuit voltage (V oc) of solar cells is crucial to optimize their photovoltaic performance. Here, we demonstrate experimentally that nanostructured layers can achieve a fundamentally larger Fermi level splitting, and thus a larger V oc, than planar layers. By etching tapered nanowires from planar indium phosphide (InP), we directly compare planar and nanophotonic geometries with the exact same material quality. We show that the external radiative efficiency of the nanostructured layer at 1 sun is increased by a factor 14 compared to the planar layer, leading to a 70 mV enhancement in V oc. The higher voltage arises from both the enhanced outcoupling of photons, which promotes radiative recombination, and the lower active material volume, which reduces bulk recombination. These effects are generic and promise to enhance the efficiency of current record planar solar cells made from other materials as well.