Over the past several years, the internal quantum efficiency for state of the art organic photovoltaic devices has approached unity. This has been in large part due to precise understanding and control of the morphology present and phenomena occurring within the devices. However, despite the gains achieved in efficient photocurrent production, the open-circuit voltage (VOC) of organic devices are generally low and serves as a substantial limit to overall device performance. The poor open-circuit voltages can ultimately be traced back to limitations imposed by fullerenes which, despite their widespread use, typically between exhibit voltages of only 0.6 ‑ 0.8 V. Intermolecular symmetry breaking charge transfer (SBCT) has the potential to reduce the losses by creating a system where the electron and hole are spatially separated, lowering the strength of their coulombic interaction. A zinc chlorodipyrrin (ZCl) is shown to undergo SBCT in polar environments similar to the D/A interface. In OPVs with the same donor, tetraphenyldibenzoperiflanthene (DBP), a ZCl acceptor yields a VOC of 1.33 V, 0.45 V larger than the analogous device with C60. The dramatic increase in VOC and concominant increase in CT state energy reveals that devices containing ZCl are able to separate charges with significantly lower recombination losses. The results presented for ZCl are the first documented application of a material which undergoes SBCT in an OPV and the resultant VOC illustrate the great potential of this family of materials, and the application of SBCT in general, in OPVs.

Symmetry breaking charge transfer in zinc dipyrrins for OPVs with open circuit voltage in excess of 1.3 V

249th National Meeting (2015)

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