10 Proposal for Future Organic Solar Cells
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Fig. 10.8 a Localized model of the non-radiative recombination from CT state to ground state.
b Delocalized model of the non-radiative recombination from CT state to ground state. c Absorption
and EL emission from CT state for 6T/PTCDI-C8 system exhibiting hopping conduction showed
a large Stokes shift. Absorption by CT is represented by the edge of the EQE (external quantum
efficiency) spectrum. d Absorption and EL emission for single-crystal Si exhibiting band conduction
showed a little Stokes shift. d Reproduced with permission from W. Warta et al., Phys. Rev. Appl.,
Copyright 2015 American Physical Society
Even if the bimolecular recombination occurs between completely separated electron
and hole, non-radiative recombination occurs through the CT state (Fig. 10.8a).
On the other hand, the organic semiconductors showing the band conduction
are represented by the delocalized model (Fig. 10.8b). In this case, since there is a
small Stokes shift between the ground state and CT state due to the little reorganization energy, little vibrational coupling suppresses the non-radiative recombination.
This coincides well with the small Stokes shift observed for the single-crystal Si
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Fig. 10.8 a Localized model of the non-radiative recombination from CT state to ground state.
b Delocalized model of the non-radiative recombination from CT state to ground state. c Absorption
and EL emission from CT state for 6T/PTCDI-C8 system exhibiting hopping conduction showed
a large Stokes shift. Absorption by CT is represented by the edge of the EQE (external quantum
efficiency) spectrum. d Absorption and EL emission for single-crystal Si exhibiting band conduction
showed a little Stokes shift. d Reproduced with permission from W. Warta et al., Phys. Rev. Appl.,
Copyright 2015 American Physical Society
Even if the bimolecular recombination occurs between completely separated electron
and hole, non-radiative recombination occurs through the CT state (Fig. 10.8a).
On the other hand, the organic semiconductors showing the band conduction
are represented by the delocalized model (Fig. 10.8b). In this case, since there is a
small Stokes shift between the ground state and CT state due to the little reorganization energy, little vibrational coupling suppresses the non-radiative recombination.
This coincides well with the small Stokes shift observed for the single-crystal Si