1. Institut für Physik, Universit?t Augsburg, 86135 Augsburg, Germany;2. Institut für Physik, Universit?t Augsburg, 86135 Augsburg, GermanyPhone: +49‐821‐5983403, Fax: +49‐821‐5983425
Abstract:
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 (Voc) of approximately 1.2 V for poly(3‐hexylthiophene) and almost 1.4 V for heat treated α‐sexithiophene. Those values are close to the maximum Voc attainable for these material systems.
