Light Energy Conversion Using Mixed Molecular Nanoclusters. Porphyrin and C60Cluster Films for Efficient Photocurrent Generation

Abstract

Composite molecular nanoclusters of fullerene and porphyrin prepared in acetonitrile/toluene mixed solvent absorb light over the entire spectrum of visible light. Upon slow evaporation of the solvent on the copper grid, these mixed nanoclusters undergo close-packed stacking to produce either tubular- or square-shaped microcrystallites and differ from those obtained from single-component clusters. The highly colored composite clusters can be assembled as 3-dimensional arrays onto nanostructured SnO2 films using an electrophoretic deposition approach. The composite cluster films exhibit an incident photon-to-photocurrent efficiency (IPCE) as high as 17% at an applied potential of 0.2 V vs SCE, which is significantly higher than the additive effect observed from either porphyrin (IPCE = 1.6%) or fullerene clusters (IPCE = 5.0%) under similar photoelectrochemical conditions. The high IPCE values observed with porphyrin and C60 clusters demonstrate the synergy of these systems toward yielding efficient photoinduced charge separation within these composite nanoclusters.