Effect of gold nanoparticles on the efficiency of poly(3-hexylthiophene): phenyl-C61-butyric-acid-methylester solar cells.

Different surface densities of gold nanoparticles (AuNPs) were deposited on (3-aminopropyl)-trimethoxysilane (APTMS)-modified indium tin oxide (ITO) electrode. The electrodes were then used in poly(3-hexylthiophene): phenyl-C61-butyric-acid-methylester (P3HT:PCBM) solar cells. Enhanced photo-conversion efficiency was observed from solar cells containing adsorbed AuNPs with surface density equals to 10 +/- 3 NPs/microm2. For higher surface densities (215 +/- 10 NPs/microm2), the presence of the plasmonic material significantly reduced the efficiency of the solar cell. Impedance spectroscopy (IS) indicates changes of the electrical characteristics, evident by a drastic reduction of the impedance relative to the reference cells, from electrodes modified with high densities of AuNPs.