- It is demonstrated that higher temperature and C 60 oxygen depletion increase the photocurrent of fullerene photoelectrochemical solar cells (PEC). Fullerene/iodide electrolyte PEC consisting of intrinsic single crystal C 60 in either aqueous 3 M KI, 0.01 M I 2 , or 0.1 M tetrabutyl ammonium iodide, 0.3 M LiClO 4 in acetonitrile solution, drive regenerative photoinduced iodide oxidation. The photocurrent is increased by an order of magnitude (to 6.4 lA/cm2 under 100 mW/cm2 illumination) by an increase of the aqueous cell temperature from 24i Ct o 82iC. A similar order of magnitude increase in photocurrent is accomplished by O 2 depletion pretreatment (24 h at 400iC in Ar) of the C 60 to improve conductivity. However, this latter treatment also irreversibly increases the cell dark current. The spectral action of single crystal C 60 is also probed, through the generated photoelectrochemical current in iodide, ferricyanide and sulfuric electrolytes as a function of wavelength. Band edges are observed at 720 nm (1.7 eV) and 560 nm (2.2 eV), and a substantial peak photocurrent response occurs at 395 nm (3.1 eV) and decreases at shorter wavelengths. ( 1998 Elsevier Science B.V. All rights reserved.