Reducing optical losses in organic solar cells using microlens arrays: theoretical and experimental investigation of microlens dimensions

• DOI: 10.1039/c4cp05221h
• Publication Date: 2014-12-19T07:36:56Z
• Authors: Yuqing Chen; Moneim Elshobaki; Ryan Gebhardt; Stephen Bergeson; Max Noack; Joong-Mok Park; Andrew C. Hillier; Kai-Ming Ho; Rana Biswas; Sumit Chaudhary
• Keywords: Microlens

The performance of organic photovoltaic devices is improving steadily and efficiencies have now exceeded 10%. However, the incident solar spectrum still largely remains poorly absorbed. To reduce optical losses, we employed a microlens array (MLA) layer on side glass substrate facing light; this approach does not interfere with processing active-layer. We observed up to 10% enhancement in short circuit current poly({4,8-bis[(2-ethylhexyl)oxy]benzo[1,2-b:4,5-b']dithiophene-2,6-diyl}{3-fluoro-2-[(2-ethylhexyl)carbonyl] thieno[3,4-b]thiophenediyl}):(6,6)-phenyl C71-butyric acid methyl ester (PTB7:PC71BM) OPV cells. Theoretically experimentally investigating several MLA dimensions, found that photocurrent increases ratio height pitch size MLA. Simulations reveal mechanisms: focuses light, also light path within active-layer by diffraction. Photocurrent enhancements increase for polymer system thinner active-layers, as demonstrated poly[N-9'-heptadecanyl-2,7-carbazole-alt-5,5-(4',7'-di-2-thienyl-2',1',3'-benzothiadiazole)] (PCDTBT):PC71BM OPVs 17% improvement current.