Performance improvement of organic bulk-heterojunction solar cells using complementary plasmonic gold nanorods

Organic bulk-heterojunction solar cells have been intensively studied recently because of their high performance and simple fabrication process. In this work, we improved the performance of poly[4,8-bis(5-(2-ethylhexyl)thiophen-2-yl)benzo[1,2-b:4,5-b0]dithiophene-co-3-fluorothieno[3,4-b]thiophene-2-carboxylate]:[6,6]-phenyl-C70-butyric acid methyl ester (PTB7-Th:PC71BM)-based organic solar cells (OSCs) by adding a hydrophilic gold nanorod (Au NR) mixture to the hole transport layer and a hydrophobic Au NR mixture to the active layer. The cooperative localized surface plasmon resonance effect of a Au NR mixture containing Au NRs with lengths of 23, 35, and 47 nm enhanced light absorption of the OSCs over a broad wavelength range. Consequently, the average power conversion efficiency (PCE) of the OSCs was significantly improved from 8.82 to 9.89%, owing mainly to improvement of the short-circuit current density (from 16.3 to 17.9 mA cm⁻²). The highest PCE of 10.31% was obtained in the best plasmonic OSC, demonstrating that doping with complementary Au NR mixtures is a simple and effective method of fabricating high-performance thin film OSCs