Anion Photoelectron Spectroscopy of Rubrene: Molecular Insights into Singlet Fission Energetics
Published on 2017-09-14T14:29:31Z (GMT) by
Rubrene (C<sub>42</sub>H<sub>28</sub>, RUB) has been seen to be attractive as a promising building block for organic semiconductors. By means of gas-phase anion photoelectron spectroscopy, the adiabatic electron affinity for RUB molecules is determined to be 1.48 ± 0.03 eV, and the S<sub>0</sub>–T<sub>1</sub> and S<sub>0</sub>–S<sub>1</sub> transition energies of RUB are evaluated to be 1.16 ± 0.05 and 2.42 ± 0.05 eV, showing the possibility of singlet fission in terms of energy. The photoelectron spectra indicate that the vibronic coupling in RUB is similar in the neutral electronic states of S<sub>0</sub>, T<sub>1</sub>, and S<sub>1</sub>. Quantum chemistry calculation results demonstrate that the vibronic coupling in these states originates from their similarly restricted structural displacement upon photoexcitation. Molecular insights into energetics suggest the important role of a charge transfer state in singlet fission.