We demonstrate a dramatic enhancement of the cathodic photocurrent of a photoelectrochemical (PEC) device based oil the Langmuir-Blodgett (LB) film of poly(3-hexylthiophene) (P3HT) by doping with Dy@C-82, which is attributed to the facile photoinduced electron transfer between P3HT and Dy@C82. The photocurrent efficiency of the P3HT/Dy@C-82 PEC device is found to be composition dependent, which is the highest when the molar ratio of P3HT:Dy@C-82 is 20:1. The optimal PEC performance is strongly correlated with the ordered molecular arrangements. A possible mechanism for the cathodic photocurrent generation is proposed and supported by the studies on the bilayer PEC device. (C) 2004 Elsevier B.V. All rights reserved.