A modular molecular photovoltaic system based on phospholipid/alkanethiol hybrid bilayers: photocurrent generation and modulation.

Monolayer quantities of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC), incorporated with either fullerenes or ruthenium tris(bipyridyl) (Ru(bpy)(3)(2+)) complexes, were formed on ferrocene-terminated C11-alkanethiol self-assembled monolayers (SAMs) through lipid fusion. Thus formed hybrid structures are characterized by quartz crystal microbalance, UV-vis spectroscopy, cyclic voltammetry and impedance analysis. In comparison to lipid monolayers deposited on C12-alkanethiol SAMs, photocurrent generation from these ferrocene-based structures is significantly modulated, displaying attenuated anodic photocurrents and enhanced cathodic photocurrents. While a similar trend was observed for the two photoagents studied, the degree of such modulations was always found to be greater in fullerene-incorporated bilayers. These findings are evaluated in the context of the film structure, energetics of the involved photo(electrochemical) species and cross-membrane electron-transfer processes.