Enhanced Photoelectrochemical Response of Polythiophene Photoelectrodes with Controlled Arrays of Silver Nanocubes

In the present work silver nanoparticles (cubes and spheres) with sizes of 40 ± 5 nm have been synthesized by a similar experimental method in order to optimize both the photoluminescence and photoelectric conversion enhancement factor of poly(3-hexylthiophene) photoelectrodes with thickness comparable to those used in organic solar cells. The silver nanoparticles were assembled into monolayers with various coverage densities using the Langmuir-Blodgett technique. The dependence of surface plasmon evanescent field and energy transfer has been investigated with the largest enhancement in photoluminescence observed at approximately 14% coverage density of silver nanocubes. We attribute the enhancement to a strong local electric field as well as scattering properties associated with particles of this geometry that translate to significant photocurrent enhancements. The mean photoluminescence lifetimes of the photoelectrode decreased with decreasing silver nanocube spacing and represent an increase in the total decay rate by a factor of 1.24 at 14% coverage of the nanoarrays. The origin of this increase is due to enhancement in either the radiative and/or nonradiative decay rates.