An Al/porphyrin Schottky barrier cell with an equimolar mixed solid of a weak electron-donating zinc porphyrin such as 5,10,15,20-tetra(2,5-dimethoxyphenyl)porphyrinatozinc (Zntpp(OMe)(2)) and a weak electron-accepting metal-free porphyrin such as 5,10,15-triphenyl-20-(3-pyridyl)porphyrin (H(2)pyp(3)p) shows much larger photocurrent compared to the cells with the pure Zntpp(OMe)(2) solid and with the pure H(2)pyp(3)p solid. Relatively large values, short-circuit photocurrent quantum yield of 18.9%, open-circuit photovoltage of 0.79 V, fill factor of 0.23, and energy conversion yield of 1.21% are obtained for the cell with the mixed solid when illuminated by a monochromatic light of 445 nm with light intensity of 7 mu W cm(-2). The series resistance of the mixed solid cell is as large as that of the pure Zntpp(OMe)(2) cell; the potential gradient in the depletion layer near the Al/mixed solid interface is smaller than that near the Al/pure Zntpp(OMe)(2) solid interface; and the exciton diffusion lengths in the pure Zntpp(OMe)(2) solid, the pure H(2)pyp(3)p solid, and the mixed solid are almost the same. Thus, the photocurrent enhancement for the mixed solid is not explained by these factors. The enhancement is interpreted by the ease of a photoinduced intramolecular electron transfer of a porphyrin heterodimer produced by an axial coordination of pyridyl group in H(2)pyp(3)p to zinc ion in Zntpp(OMe)(2) in the mixed solid because the charge-separated dimer can separate to a free electron and a free hole under a large electric field formed near the Al/porphyrin interface much more easily than the excited pure porphyrins.