Abstract—The photovoltaic properties ofmeso‐tetraphenylporphyrin and its derivatives with variouspara‐substituents, meso‐tetrakis(2,4‐dimethoxyphenyl)porphyrin andmeso‐tetrakis (2‐fluorenyl)porphyrin have been investigated. The forward dark current‐voltage characteristics of Al/porphyrin/Ag cells are attributed to the MIS Schottky barriers consisting of Al/Al2O3/porphyrin. The barrier parameters such as the apparent diffusion potentialV0the barrier width w0and the density of ionized impurityNare estimated by using the capacitor discharge method. The action spectra of photocurrents closely follow the optical absorption spectra of the porphyrin films. The photocurrents vary asipαIγ, whereIis the incident light intensity, and the Sight exponentsyrange between 0.83 and 1.0. The sublinear difference from unity could be related to the exponential distribution of hole traps in films of the porphyrins. No obvious correlation between the photocurrent and the fluorescence quantum yields of the sublimed porphyrin films is found. The electron donating substituents such as OCH3and CH3strikingly increase the photocurrents. The photocurrent quantum yields correlate exponentially with the first ring oxidation potentials of the porphyrins and also with the substituent constants for the Hammett linear free‐energy relationship. The current quantum yields estimated for the porphyrins studied, range in the order of 10‐4–10‐2with power conversi