Developing New Functional TCs
David Ginley, Lauren Garten, Thomas Gennett, Paul Ndione, Maikel van Hest,
Shruti Aggarwal, Ragiv Singh, Stephan Lany and John Perkins
NREL, Golden Colorado 80401
Mike Toney and Laura Schelhas,
SLAC,
Joel Ager
, LBNL
Cynthia Lo
, Washington University Saint Louis
Transparent Conductors (TCs) are increasingly critical to the performance and reliability of a
number of technologies. Traditionally based primarily on oxides the class is rapidly
expanding into new materials including both other oxides and composites. Many of these
materials offer unique functionality as well as processing and reliability advantages over
some of the historic materials such as ZnO and ITO. More to the point, oxide, non-oxide and
composite materials are being collectively looked at for an increasingly broad set of
applications including photovoltaics, solid state lighting, power electronics and a broad class
of flexible and wearable electronics. In this talk, we will focus on two main areas; the
development of predictive models to be able to identify dopants and the processing regimes
where they can be activated as well as the use of nanowire oxide composites to develop a
new generation of tunable high performance TC.
Increasingly, the demands on TCs for performance, processibility and reliability are driving a
search for new materials. The ability to use materials genomics to identify new dopable TC
materials that are experimentally realizable is rapidly increasing. We will discuss recent
work on predicting the dopability of Ga
2
O
3
films which potentially have broad applicability
as buffer layers, TCOs, and in power electronics if the doping level can be well controlled.
We will also present resent results on the theoretical prediction and realization of a new p-
type TC based on CuZnS which has demonstrated conductivities of up to 100 S/cm. We will
discuss the theoretical predictions for the process windows to activate both Sn and Si as
dopants and compare this to experimental results and the literature. This will illustrate the
evolving tools both theory and experiment to develop and realize dopants in wide band gap
materials.
In cases where single materials may not be sufficient, the prospects of composite materials is
increasingly attractive. For example, Ag, and potentially Cu, nanowires embedded in a metal
oxide matrix can potentially produce TCs that can be processed at low temperature, have
conductivity and transparency comparable to the best TCOs, control interface stability and
electronic properties and are suitable to flexible electronics. We will present work on ZnO,
InZnO and ZnSnO composites with Ag nanowires where the performance can be as good as
high quality InSnO with films Rs< 10 Ohms/sq. We will discuss the dependence on the
interrelationship between the nanowire properties and the oxide properties. We will also
discus the concept of employing sandwich oxides to separately optimize the top and bottom
interfacial properties.
This work was supported, in part, by the Center for the Next Generation of Materials by
Design, an Energy Frontier Research Center funded by the U.S. Department of Energy,
Office of Science, Basic Energy Sciences. This research also supported in part by the Solar
Energy Research Institute for India and the U.S. (SERIIUS) funded jointly by the U.S.
Department of Energy subcontract DE AC36-08G028308 (Office of Science, Office of Basic
Energy Sciences, and Energy Efficiency and Renewable Energy, Solar Energy Technology
Program, with support from the Office of International Affairs) and the Government of India
subcontract IUSSTF/JCERDC-SERIIUS/2012 dated 22nd Nov. 2012.
PO 3
-71-
