Ultrathin organic bulk heterojunction solar cells: Plasmon enhanced performance using Au nanoparticles

The plasmonic effect of gold nanoparticles (AuNPs) enhances light absorption and, thus, the efficiency of organic bulk heterojunction solar cells with poly (3-hexylthiophene) (P3HT): [6,6]-phenyl-C ₆₁-butyric acid methyl ester (PCBM) as active layer. We report optimization of this enhancement by varying the attachment density of the self-assembled AuNPs on silanized ITO using N ¹-(3-trimethoxysilylpropyl)diethylenetriamine. Using finite difference time domain simulations, the thicknesses of poly (3,4- ethylenedioxythiophene) (PEDOT): poly (styrenesulfonate) (PSS) and P3HT:PCBM layers were suitably varied to ensure broadband optical absorption enhancement and minimal exciton quenching within the active layer. Our experimental results demonstrate that for solar cell structures with 20 surface coverage, absorption is increased by 65 as predicted by simulations. Further, we show that AuNPs increase the efficiency by 30 and that silanization of ITO positively impacts device performance.