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

Abstract

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 ED (EA) in the band gap is proposed. The photovoltaic effect is due to the transfer of energy of molecular excitons S1 to neutral A(D) and ionized A−(D+) impurities followed by the formation of electrons and holes: S1 + D(A) → D+(A−) + e−(h+) and S1 + 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 Ed, Nd (Ea, Na). The values of rate constants that ensure the maximum quantum yield of conversion are discussed.