Subwavelength nanostructures integrated with polymer-packaged iii-v solar cells for omnidirectional, broad-spectrum improvement of photovoltaic performance

• Published in: Progress in photovoltaics 2015-10, Vol.23 (10), p.1398-1405
• Main Authors: Li, Xiaohan, Li, Ping-Chun, Ji, Li, Stender, Christopher, McPheeters, Claiborne, Tatavarti, Sudersena Rao, Sablon, Kimberly, Yu, Edward T.
• Format: Article
• Language: English
• Subjects: antireflection; Antireflection coatings; broad spectrum; Current density; Dielectrics; Incidence; Nanostructure; omnidirectional; Packaging; Photovoltaic cells; Quantum efficiency; Solar cells; subwavelength
• ISSN: 1062-7995; 1099-159X
• DOI: 10.1002/pip.2565

Reduction in surface and interface reflectance via the integration of subwavelength nanostructures in flexible polymer packaging material combined with incorporation of dielectric nanoislands into a conventional two‐layer antireflection coating has been demonstrated, analyzed and optimized. Transmittance measurements of moth‐eye textured polymer packaging sheets with different tapered pillar heights fabricated by reactive‐ion etching and nanosphere lithography provide insights into the choice of the optimum nanostructure dimensions. Detailed computational modeling and simulations elucidate the physical nature of the antireflection performance of dielectric nanoisland structures integrated with a commercial two‐layer antireflection coating, and provide guidance for design of the nanoisland structure for optimum antireflection performance. Measurements show that the integration of appropriately designed nanostructures in both polymer packaging material and conventional antireflection layers enables substantial increases in external quantum efficiency (E.Q.E.) and short‐circuit current density (Jsc) over a broad range of incident angles, compared to structures with conventional bilayer antireflection coatings and unpatterned polymer packaging sheets. A 1.1× increase in Jsc, derived directly from E.Q.E. measurements, at normal incidence, increasing to 1.67× improvement at 80° angle of incidence, suggests that such an approach is promising for a variety of photovoltaic applications, particularly those where solar tracking is not feasible or practical. Copyright © 2014 John Wiley & Sons, Ltd. The integration of subwavelength‐scale dielectric nanostructures on both the conventional two‐layer antireflection coating and the polymer packaging sheet provides reduced surface and interface reflectance for III/V solar cells. Calculations derived from external quantum efficiency measurements show that the simultaneous use of moth‐eye textured polymer packaging sheet and Al2O3 nanoisland structure enables increase in short‐circuit current density of ~1.1× to 1.67×, depending on angle of incidence, compared to structures using conventional two‐layer antireflection coating and unpatterned polymer packaging sheet.