Design and synthesis of novel p-type TCOs: From computational screening towards
film deposition
Gilles Bonneux
1
, Ken Elen
1
, Nasrin Sarmadian
2
, Christophe Detavernier
3
, Dirk Lamoen
2
,
Bart Partoens
2
, An Hardy
1
, Marlies Van Bael
1
1
Hasselt University, Institute for Materials Research (IMO), Inorganic and Physical
Chemistry, and IMEC vzw, division IMOMEC, Martelarenlaan 42, 3500 Hasselt
2
Antwerp University, Department of Physics, Groenenborgerlaan 171, 2020 Antwerpen
3
Ghent University, Department of Solid-State Sciences, CoCooN Research Group,
Krijgslaan 281/S1, 9000 Gent
Over the last decades, great progress has been made in the field of n-type TCO materials for
various opto-electronic applications. This already resulted in the device implementation and
commercialization of many oxides. However, p-type TCO materials research is still in a
fundamental stage, and materials science has yet to find a solution to the generally low carrier
mobilities in these materials. Especially for the design of transparent electronics, the
availability of transparent p-n junctions is critical for many electronic components.
Using modern day’s widespread availability of material databases in combination with
powerful computational techniques allows for high-throughput screenings of thousands of
oxides in search of various desired properties. For potential TCO candidates, parameters such
as the carrier effective mass, the optical band gap and the (extrinsic) dopability are having
high priorities
[1, 2]
.
The candidates resulting from these screenings are often complex multi-metal oxides, in
which the matrix material typically requires the addition of external acceptor dopants. All in
all, these requirements contribute to the fact that the synthesis of these “designer oxides” is
often not straightforward. Additionally, the synthesis should be implemented in a process that
ultimately leads to the fabrication of functional oxide films. By depositing these thin films
using chemical solution deposition (CSD) instead of more traditional vacuum techniques, we
can overcome some challenges that come along with the deposition of multi-metal oxides,
such as homogeneity issues and control of the stoichiometry, including dopant addition.
In this work, two recent p-type TCO candidate materials were selected for further study: Li-
doped Cr
2
MnO
4
[1]
and Na-doped Ln
2
SeO
2
(Ln: lanthanide)
[2]
. Both of these materials are
identified as primary candidates from their respective computational screening procedures.
Aqueous precursor solutions for both materials are developed, in which the metal ions are
stabilized by α-hydroxy carboxylic acids which fulfill the role of ligands. Thin films of these
materials are deposited via spin-coating. Ultimately, a thermal treatment (combined with a
selenization step for material 2) leads to crystalline films of the desired phase. The resulting
films are characterized further via XRD (phase formation) and SEM (morphology). In
addition, issues regarding phase formation are investigated and circumvented by optimizing
the synthesis and processing steps.
Acknowledgements:
This research is financially supported by the Research Foundation-
Flanders (FWO Vlaanderen, project nr. G054312N and G018914N)
References:
[1]:
Peng et al.,
Adv. Funct. Mater.
2013,
23
(42), 5267-5276
[2]:
Sarmadian et al.,
Sci. Rep.
2016,
6
, 20446
O 36
-94-
