TY - JOUR
T1 - The Roles of Structural Order and Intermolecular Interactions in Determining Ionization Energies and Charge-Transfer State Energies in Organic Semiconductors
AU - Graham, Kenneth
AU - Ngongang Ndjawa, Guy Olivier
AU - Conron, Sarah M.
AU - Munir, Rahim
AU - Vandewal, Koen
AU - Chen, John J.
AU - Sweetnam, Sean
AU - Thompson, Mark E.
AU - Salleo, Alberto
AU - Mcgehee, Michael D.
AU - Amassian, Aram
N1 - KAUST Repository Item: Exported on 2020-10-01
Acknowledgements: K.R.G. and G.O.N.N. contributed equally to this work. K.R.G. and A.A. acknowledge SABIC for a postdoctoral fellowship. G.O.N.N., K.R.G., M.D.M., and A.A. acknowledge the KAUST GCR for a GRP-CF award. M.D.M. and S.S. acknowledge support from the Department of the Navy, Office of Naval Research Award No. N00014-14-1-0580. J.J.C and M.E.T. acknowledge support from the National Science Foundation Award No. CBET 1511757. Use of the Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, is supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences under Contract No. DE-AC02-76SF00515.
PY - 2016/8/17
Y1 - 2016/8/17
N2 - The energy landscape in organic semiconducting materials greatly influences charge and exciton behavior, which are both critical to the operation of organic electronic devices. These energy landscapes can change dramatically depending on the phases of material present, including pure phases of one molecule or polymer and mixed phases exhibiting different degrees of order and composition. In this work, ultraviolet photoelectron spectroscopy measurements of ionization energies (IEs) and external quantum efficiency measurements of charge-transfer (CT) state energies (ECT) are applied to molecular photovoltaic material systems to characterize energy landscapes. The results show that IEs and ECT values are highly dependent on structural order and phase composition. In the sexithiophene:C60 system both the IEs of sexithiophene and C60 shift by over 0.4 eV while ECT shifts by 0.5 eV depending on molecular composition. By contrast, in the rubrene:C60 system the IE of rubrene and C60 vary by ≤0.11 eV and ECT varies by ≤0.04 eV as the material composition varies. These results suggest that energy landscapes can exist whereby the binding energies of the CT states are overcome by energy offsets between charges in CT states in mixed regions and free charges in pure phases. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
AB - The energy landscape in organic semiconducting materials greatly influences charge and exciton behavior, which are both critical to the operation of organic electronic devices. These energy landscapes can change dramatically depending on the phases of material present, including pure phases of one molecule or polymer and mixed phases exhibiting different degrees of order and composition. In this work, ultraviolet photoelectron spectroscopy measurements of ionization energies (IEs) and external quantum efficiency measurements of charge-transfer (CT) state energies (ECT) are applied to molecular photovoltaic material systems to characterize energy landscapes. The results show that IEs and ECT values are highly dependent on structural order and phase composition. In the sexithiophene:C60 system both the IEs of sexithiophene and C60 shift by over 0.4 eV while ECT shifts by 0.5 eV depending on molecular composition. By contrast, in the rubrene:C60 system the IE of rubrene and C60 vary by ≤0.11 eV and ECT varies by ≤0.04 eV as the material composition varies. These results suggest that energy landscapes can exist whereby the binding energies of the CT states are overcome by energy offsets between charges in CT states in mixed regions and free charges in pure phases. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
UR - http://hdl.handle.net/10754/622125
UR - http://onlinelibrary.wiley.com/doi/10.1002/aenm.201601211/full
UR - http://www.scopus.com/inward/record.url?scp=84982224378&partnerID=8YFLogxK
U2 - 10.1002/aenm.201601211
DO - 10.1002/aenm.201601211
M3 - Article
SN - 1614-6832
VL - 6
SP - 1601211
JO - Advanced Energy Materials
JF - Advanced Energy Materials
IS - 22
ER -
