Relating the open-circuit voltage to interface molecular properties of donor:acceptor bulk heterojunction solar cells

Abstract

The open-circuit voltage (Vococ is proportional to the energy of the CT states ECT. The energetic loss qΔV between ECT and q Voc vanishes when approaching 0 K. It depends linearly on T and logarithmically on illumination intensity. Furthermore qΔV can be reduced by decreasing the electronic coupling between polymer and fullerene or by reducing the nonradiative recombination rate. For the investigated devices we find a loss qΔV of ∼0.6eV at room temperature and under solar illumination conditions, of which ∼0.25eV is due to radiative recombination via the CT state and ∼0.35eV is due to nonradiative recombination. © 2010 The American Physical Society.