Electrical characteristics of chlorophyll a films

Abstract

Dark conductivity and photovoltaic effects have been investigated in thin film samples of chlorophyll a. Samples were fabricated by depositing monomolecular layers of chlorophyll a on to conducting glass and metal substrates. The dependence of the dark current on temperature and voltage in 10 monolayer samples at low voltages (< 500 mV) is consistent with a conductivity tunnelling process. At higher voltages the conductivity characteristics are consistent with conductivity tunnelling, Schottky emission and the Frenkel-Poole effect. An enhanced photovoltaic effect is found in chlorophyll a films (100 monolayers) composited with electron acceptor and donor materials. The results are discussed in terms of energy migration in photosynthetic units.