TY  - JOUR
A1  - Vandewal, Koen
A1  - Benduhn, Johannes
A1  - Schellhammer, Karl Sebastian
A1  - Vangerven, Tim
A1  - Rückert, Janna E.
A1  - Piersimoni, Fortunato
A1  - Scholz, Reinhard
A1  - Zeika, Olaf
A1  - Fan, Yeli
A1  - Barlow, Stephen
A1  - Neher, Dieter
A1  - Marder, Seth R.
A1  - Manca, Jean
A1  - Spoltore, Donato
A1  - Cuniberti, Gianaurelio
A1  - Ortmann, Frank
T1  - Absorption Tails of Donor
BT  - C-60 Blends Provide Insight into Thermally Activated Charge-Transfer Processes and Polaron Relaxation
JF  - Journal of the American Chemical Society
N2  - In disordered organic semiconductors, the transfer of a rather localized charge carrier from one site to another triggers a deformation of the molecular structure quantified by the intramolecular relaxation energy. A similar structural relaxation occurs upon population of intermolecular charge-transfer (CT) states formed at organic electron donor (D)-acceptor (A) interfaces. Weak CT absorption bands for D A complexes occur at photon energies below the optical gaps of both the donors and the C-60 acceptor as a result of optical transitions from the neutral ground state to the ionic CT state. In this work, we show that temperature-activated intramolecular vibrations of the ground state play a major role in determining the line shape of such CT absorption bands. This allows us to extract values for the relaxation energy related to the geometry change from neutral to ionic CT complexes. Experimental values for the relaxation energies of 20 D:C-60 CT complexes correlate with values calculated within density functional theory. These results provide an experimental method for determining the polaron relaxation energy in solid-state organic D-A blends and show the importance of a reduced relaxation energy, which we introduce to characterize thermally activated CT processes.
Y1  - 2017
U6  - https://doi.org/10.1021/jacs.6b12857
SN  - 0002-7863
VL  - 139
IS  - 4
SP  - 1699
EP  - 1704
PB  - American Chemical Society
CY  - Washington
ER  - 
TY  - JOUR
A1  - Schwarze, Martin
A1  - Schellhammer, Karl Sebastian
A1  - Ortstein, Katrin
A1  - Benduhn, Johannes
A1  - Gaul, Christopher
A1  - Hinderhofer, Alexander
A1  - Toro, Lorena Perdigon
A1  - Scholz, Reinhard
A1  - Kublitski, Jonas
A1  - Roland, Steffen
A1  - Lau, Matthias
A1  - Poelking, Carl
A1  - Andrienko, Denis
A1  - Cuniberti, Gianaurelio
A1  - Schreiber, Frank
A1  - Neher, Dieter
A1  - Vandewal, Koen
A1  - Ortmann, Frank
A1  - Leo, Karl
T1  - Impact of molecular quadrupole moments on the energy levels at organic heterojunctions
JF  - Nature Communications
N2  - The functionality of organic semiconductor devices crucially depends on molecular energies, namely the ionisation energy and the electron affinity. Ionisation energy and electron affinity values of thin films are, however, sensitive to film morphology and composition, making their prediction challenging. In a combined experimental and simulation study on zinc-phthalocyanine and its fluorinated derivatives, we show that changes in ionisation energy as a function of molecular orientation in neat films or mixing ratio in blends are proportional to the molecular quadrupole component along the p-p-stacking direction. We apply these findings to organic solar cells and demonstrate how the electrostatic interactions can be tuned to optimise the energy of the charge-transfer state at the donor-acceptor interface and the dissociation barrier for free charge carrier generation. The confirmation of the correlation between interfacial energies and quadrupole moments for other materials indicates its relevance for small molecules and polymers.
Y1  - 2019
U6  - https://doi.org/10.1038/s41467-019-10435-2
SN  - 2041-1723
VL  - 10
PB  - Nature Publ. Group
CY  - London
ER  -