The photovoltaic properties of organic cells based on a polythiophene film have been studied. An external power efficiency of 10(-4)% has been obtained in the pristine polymer diode. In order to improve this result, three complementary routes have been investigated. Optical sensitization of the polythiophene with a dye of the indane group leads to a 75 increase in power efficiency. A hybrid molecular/polymeric p-n type junction instead of the original Schottky type provides a 0.15% efficiency. Molecular rectification in oriented polymers incorporating diodelike chromophores increases the PV efficiency by a factor of 40. (C) 2000 Elsevier Science B.V. All rights reserved.