Transparent conductive oxide electrode dependence of photocurrent characteristics in bacteriorhodopsin photocells

We investigated the photocurrent characteristics in photocells using bacteriorhodopsin (bR) thin films deposited on various kinds of transparent conductive oxide (TCO) electrodes. The photocurrent depends largely on the species of TCO and partly on the surface morphology. The photocell using a bR thin film deposited on a fluorine-doped tin oxide electrode with a textured structure showed the largest photocurrent. Our results indicate that the variation of capacitance near the interface induced by the bRʹs light-driven proton pump function affects the transient photocurrent, while the capacitance near the interface is produced by the TCO electrode, bR thin film, and electrolyte solution.