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TY  - THES
AU  - Schröder, Sonja
TI  - Structural and electronic characterization of hetero-organic NTCDA-CuPc adsorbate systems on Ag(111)
PB  - RWTH Aachen
VL  - Dissertation
CY  - Aachen
M1  - RWTH-2016-00216
SP  - 1 Online-Ressource (154 Seiten) : Illustrationen, Diagramme
PY  - 2016
N1  - Veröffentlicht auf dem Publikationsserver der RWTH Aachen University
N1  - Dissertation, RWTH Aachen, 2015
AB  - Organic solar cells have many advantages compared to inorganic devices e.g. lower costs, thinner active layers and easier production, but to compete with the inorganic solar cells their efficiency has to be increased. Different acceptor-donor systems therefore have to be studied as it is known that charge transport depends on molecular geometry of the unit cell. In this work a systematic study of laterally and vertically mixed structures of the charge acceptor 1,4,5,8-naphthalene-tetracarboxylic-dianhydride (NTCDA) and the donor copper-II-phthalocyanine (CuPc) adsorbed on Ag(111) is presented.Laterally mixed layers were studied, where the unit cell size and shape can be tuned by using different stoichiometric ratios of both molecules. NTCDA and CuPc form five coverage dependent mixed structures on Ag(111) with (uni-axial) commensurate substrate relations, which have surprisingly large unit cells, compared to PTCDA-CuPc heteromolecular systems. An adsorption height alignment of the molecules was found for a CuPc-rich and a NTCDA-rich phase, as was earlier observed for PTCDA and CuPc by Stadtmüller et al. The molecules are however adsorbed at lower heights compared to their homomolecular structures in the NTCDA-rich phase. Differences in the contrast of the NTCDA molecules in STM images indicate that the NTCDAs are located at different adsorption heights. The study of the electronic properties by ARPES and STS showed that the lowest unoccupied molecular orbital (LUMO) of NTCDA is more populated than in the homomolecular structure and the LUMO of CuPc is empty. This confirms the model of charge reorganization of Stadtmüller et al., who claimed that the electrons are transferred from the donor (CuPc) via the substrate to the charge acceptor (PTCDA). Our measurements proved that NTCDA is able to take up the whole charge offered by CuPc, although it is a weaker charge acceptor than PTCDA.The investigation of three differently stacked  NTCDA-CuPc systems, CuPc molecules on top of a relaxed (RML) and a compressed monolayer (CML) of NTCDA and NTCDA on a monolayer of CuPc on Ag(111), allowed for the study of the interaction between the organic layers. Molecular exchange was observed for CuPc on the RML of NTCDA and for NTCDA on a ML of CuPc. The CuPc molecules have sufficient space to adsorb between the NTCDAs of the RML. The 10 
LB  - PUB:(DE-HGF)11
UR  - https://publications.rwth-aachen.de/record/565927
ER  -