Photovoltaic Effect in Phthalocyanine-Based Organic Solar Cells: 3. Exciton Trapping Followed by Charge Carrier Generation

A kinetic model Nd(Na) of the photovoltaic effect in phthalocyanine (Pc) layers doped with a donor D (acceptor A) in concentration forming one impurity level with energy E D ( E A ) in the band gap is proposed. The photovoltaic effect is due to the transfer of energy of molecular excitons S 1 to neutral A ( D ) and ionized A − ( D + ) impurities followed by the formation of electrons and holes: S 1 + D ( A ) → D + ( A − ) + e − ( h + ) and S 1 + D + ( A − ) → D ( A ) + h + ( e − ). The quasi-stationary concentrations of charge carriers, the population of ionized impurity levels, and the energies of quasi-Fermi levels have been found as functions of light intensity and E d , N d ( E a , N a ). The values of rate constants that ensure the maximum quantum yield of conversion are discussed.