Photocurrent enhancement for polymer langmuir-blodgett monolayers containing ruthenium complex by surface plasmon resonance

This paper describes effective photocurrent generation based on a polymer Langmuir-Blodgett (LB) monolayer containing ruthenium complex on a silver electrode excited by surface plasmon resonance (SPR). It was found that photocurrent generation is greatly enhanced at an incident angle where the electromagnetic field was most enhanced by SPR. At this angle, the photocurrent is enhanced by a factor of 23.6 compared with that at the critical angle for total internal reflection. The incident monochromatic photon-to-current conversion efficiency was 9.53 × 10-³%, higher than that of the corresponding polymer LB monolayer film on a transparent indium tin oxide electrode with conventional direct transmitted light (2.87 × 10-³%). Furthermore, it was demonstrated that precoating with poly(N-dodecylacrylamide) homopolymer ensures adequate separation of the Ru(bpy)₃ ²⁺ and silver surface, thereby suppressing the quenching of photoexcited Ru(bpy)₃ ²⁺ by the silver. Controlling the distance between the Ru(bpy)₃ ²⁺ layer and the silver using the Langmuir-Blodgett technique leads to effective photoexcitation of Ru(bpy)₃ ²⁺ by SPR and suppression of quenching by the silver surface, resulting in efficient photocurrent generation.