Understanding the limits of plasmonic enhancement in organic photovoltaics

Erwin, William R.; MacKenzie, Roderick C. I.; Bardhan, Rizia

Abstract

Plasmonic enhancement in organic photovoltaics has been extensively studied in the past decade. However, the reported improvements in power conversion efficiency (PCE) are highly inconsistent due to a poor understanding of the limitations of how plasmonics affect charge generation and transport in solar cells. In this work, we address these long-standing uncharted questions as to when plasmonic enhancements are useful and when they are not. We do this with a model system consisting of poly[2,6-(4,4-bis-(2-ethylhexyl)-4H-cyclopenta[2,1-b:3,4-b?]dithiophene)-alt-4,7-(2,1,3-benzothiadiazole)]:[6,6]-phenyl C61 butyric acid methyl ester PCDTBT polymer active layer with silver nanostructures embedded in the poly(3,4-ethylenedioxythiophene):polystyrene PEDOT:PSS sulfonate hole-transport layer. We demonstrate that: (a) plasmonic enhancements are most pronounced when the charge carrier mobilities of the donor and acceptor materials are unbalanced; (b) the introduction of plasmonic nanostructures in devices with balanced charge transport usually results in a decrease in efficiency; (c) plasmonic enhancement is highly shape-dependent; (d) for devices with asymmetric mobilities, as long as the species with low mobility is extracted at the contact where light is incident, device efficiency will be boosted; and (e) increase in light absorption in the active layer has minimal impact on PCE; the efficiency is primarily driven by exciton generation and charge collection efficiency. The findings of our work provide a generalized framework to guide researchers as to when plasmonic effects could be helpful to a device and when they could degrade performance.

Citation

Erwin, W. R., MacKenzie, R. C. I., & Bardhan, R. (2018). Understanding the limits of plasmonic enhancement in organic photovoltaics. Journal of Physical Chemistry C, 122(14), 7859-7866. https://doi.org/10.1021/acs.jpcc.8b00786

• Journal Article Type: Article
• Acceptance Date: Mar 2, 2018
• Online Publication Date: Mar 2, 2018
• Publication Date: Apr 12, 2018
• Deposit Date: Oct 29, 2018
• Publicly Available Date: Mar 3, 2019
• Journal: Journal of Physical Chemistry C
• Print ISSN: 1932-7447
• Electronic ISSN: 1932-7455
• Publisher: American Chemical Society
• Peer Reviewed: Peer Reviewed
• Volume: 122
• Issue: 14
• Pages: 7859-7866
• DOI: https://doi.org/10.1021/acs.jpcc.8b00786
• Public URL: https://nottingham-repository.worktribe.com/output/1206422
• Publisher URL: https://pubs.acs.org/doi/abs/10.1021/acs.jpcc.8b00786