Approaching the ultimate open circuit voltage in thiophene based single junction solar cells by applying diindenoperylene as acceptor

The efficiency of a photovoltaic cell is directly proportional to its open circuit voltage. This in turn is eventually set by the donor-acceptor energy gap, i.e. the energy of the intermolecular charge-transfer state in organic solar cells. In this letter we study diindenoperylene (DIP) as a new molecular acceptor. We show that planar heterojunctions of thiophene derivatives and DIP yield extraordinarily high open circuit voltages (V(oc)) of approximately 1.2 V for poly(3-hexylthiophene) and almost 1.4 V for heat treated alpha-sexithiophene. Those values are close to the maximum V(oc) attainable for these material systems. (C) 2011 WILEY- VCH Verlag GmbH & Co. KGaA, Weinheim