Effect of fullerene on photocurrent performance of 6-O-porphyrin-2,3-di-O-stearoylcellulose Langmuir-Blodgett films

Thin films consisting of 6-O-porphyrin-2,3-di-O-stearoylcellulose (H2CS) and fullerene (C-60) were fabricated for anodic photocurrent generation systems by the Langmuir-Blodgett (LB) technique. The pi-complexation between the porphyrin moiety and C-60 in the LB films was investigated by means of the surface pressure (pi)-area (A) isotherms, UV-vis, and fluorescence spectroscopy. The photocurrent density generated from the H2PCS-C-60 LB monolayer films exhibited an increase with increasing the C-60 proportion and reached a maximum at a mixing ratio of 1:2, yielding a quantum yield of 12.5% and an IPCE (incident photon-to-current efficiency) of 0.50% at a bias potential of +100 mV vs. SCE. Furthermore, the LB five-layer films could give rise to the IPCE value of 1.5% at +100 mV without significant decline of the quantum yields, which was due to the function of C60 as an electron carrier to improve the interlayer electron transfer through each layer. These results have demonstrated a promising method for preparing the donor-acceptor systems using cellulose as a scaffold in the LB films.