SFB 951/2: HIOS - Adjusting energy levels of hybrid inorganic/organic heterostructures (TP A 8)

During the past funding period, we have learned how to adjust the work function of ZnO surfaces in the
interval ranging from 2.2 eV to 6.5 eV using dipolar organophosphonates and strong molecular donors/
acceptors, and we have acquired understanding of the underlying fundamental mechanisms. As a key
parameter the doping level of the inorganic semiconductor was identified. Consequently, we will now expand
the parameter space for tuning the HIOS energy level alignment by including controlled doping of the organic
semiconductor as means to impact interface energetics, which can be exploited in application-oriented CRC
projects, particularly A11 (Christiansen), B3 (Blumstengel), B7 (Neher), and B13 (List-Kratochvil).

Furthermore, we have succeeded in optimising the HIOS energy levels for energy transfer. However, the full
tunability, which would ideally cover the entire range of type-II situations (including type-I midway) across the
energy gaps of inorganic and organic component, is not achievable when doping of one component induces
Fermi-level pinning. Consequently, adjusting doping in both components must be achieved to exploit the full
potential of HIOS. To this end, we plan to expand the inorganic semiconductors to be studied to GaN and Si,
where p- and n-type doping is feasible. This opens the possibility to reach novel HIOS interface phenomena,
and we will target realizing rather extreme HIOS interface energy levels, i.e., contact-induced inversion layer
formation, which may be exploited towards (i) interfacial charge transfer and (ii) minority carrier charge injection
in highly doped inorganic and organic semiconductors.

Additional efforts will be directed at (i) exploring to what extent non-symmetric dipolar molecules can be used
in conjunction with in-plane dipoles of the ZnO(101􀴤0) surface, by controlling the competition between dipoledipole,
hydrogen-bonding, and screening van-der-Waals interactions. And (ii) how multi-functional selfassembled
monolayers can be employed for switching interface electronic levels by an external stimulus, as
well as (iii) we aim at investigating if, and if so to which extent, highly-doped ZnO [from A5 (Henneberger)]
with essentially metallic properties differs in terms of coupling with organic semiconductors and the resulting
interfacial electronic structure.

To provide improved fundamental understanding of structural and electronic HIOS interface properties our
experimental results will be compared to pertinent theoretical modelling, which will in part also guide our
selection of organic compounds [A4 (Heimel), A7 (Klapp/Dzubiella), B4 (Körzdörfer/Scheffler/Rinke)].

Koch, Norbert Prof. Dr. techn. (Details) (Struktur, Dynamik und elektron. Eigenschaften molekul. Systeme)

Projektstart: 07/2015
Projektende: 06/2019

Experimentelle Physik der kondensierten Materie

Experimentelle Physik, kondensierte Materie

T. Schultz, R. Schlesinger, J. Niederhausen, F. Henneberger, S. Sadofev, S. Blumstengel,
A. Vollmer, F. Bussolotti, J.-P. Yang, S. Kera, K. Parvez, N. Ueno, K. Müllen, N. Koch,
“Tuning the work function of GaN with organic molecular acceptors”, Phys. Rev. B 93, 125309 (2016).

T. Schultz, J. Niederhausen, R. Schlesinger, S. Sadofev, N. Koch, “Impact of surface states and
bulk doping level on hybrid inorganic/organic semiconductor interface energy levels”,
J. Appl. Phys. 123, 245501 (2018).

R. Wang, T. Katase, K.-K. Fu, T. Zhai, J. Yang, Q. Wang, H. Ohta, N Koch, S. Duhm, “Oxygen vacancies
allow tuning the work function of vanadium dioxide”, Adv. Mater. Interfaces 5, 1801033 (2018).

K.-K. Fu, R. Wang, T. Katase, H. Ohta, N. Koch, S. Duhm, “Stoichiometric and oxygen-deficient VO2
as versatile hole injection electrode for organic semiconductors”,
ACS Appl. Mater. Interfaces 10, 10552 (2018).

M. H. Futscher, T. Schultz, J. Frisch, M. Ralaiarisoa, E. Metwalli, M. V. Nardi, P. Müller-Buschbaum,
N. Koch, “Electronic properties of hybrid organic/inorganic semiconductor pn-junctions”,
J. Phys. Condens. Matter, in press, DOI:10.1088/1361-648X/aaf310 (2018).

Q. Wang, J. Frisch, M. Herder, S. Hecht, N. Koch, “Electronic properties of optically switchable
photochromic diarylethene molecules at the interface with organic semiconductors”,
ChemPhysChem 18, 722 (2017).

T. Mosciatti, M. G. del Rosso, M. Herder, J. Frisch, N. Koch, S. Hecht, E. Orgiu, P. Samorì,
“Light-modulation of the charge injection in a polymer thin-film transistor by functionalizing electrodes
with bi-stable photochromic self-assembled monolayers”, Adv. Mater. 28, 6606 (2016).

Q. Wang, G. Ligorio, V. Diez Cabanes, D. Cornil, B. Kobin, J. Hildebrandt, M. V. Nardi, M. Timpel,
S Hecht, J. Cornil, E. J. W. List-Kratochvil, N. Koch, “Dynamic photo-switching of electron energy levels
at hybrid ZnO/organic photochromic molecule junctions”, Adv. Funct. Mater. 28, 1800716 (2018).

Z. Song, T. Schultz, Z. Ding, B. Lei, C. Han, P. Amsalem, T. Lin, D. Chi, S. L. Wong, Y. J. Zheng,
M.-Y. Li, L.-J. Li, W. Chen, N. Koch, Y. L. Huang, A. T. S. Wee, “Electronic properties of a 1D
intrinsic/p-doped heterojunction in a 2D transition metal dichalcogenide semiconductor”,
ACS Nano 11, 9128 (2017).

S. Park, N. Mutz, T. Schultz, S. Blumstengel, A. Han, A. Aljarb, L.-J. Li, E. J. W. List-Kratochvil,
P. Amsalem, N. Koch, “Direct determination of monolayer MoS2 and WSe2 exciton binding energies
on insulating and metallic substrates”, 2D Mater. 5, 025003 (2018).

Zuletzt aktualisiert 2020-09-09 um 12:11