Transparent Conducting Oxides

Abstract

In the interim between the conception of this issue of MRS Bulletin on transparent conducting oxides (TCOs) and its publication, the remarkable applications dependent on these materials have continued to make sweeping strides. These include the advent of larger flat-screen high-definition televisions (HDTVs), larger and higher-resolution screens on portable computers, the increasing importance of low emissivity (“low-e”) and electrochromic windows, a significant increase in the manufacturing of thin-film photovoltaics (PV), and a plethora of new hand-held and smart devices, all with smart displays.1-7 Coupled with the increased importance of TCO materials to these application technologies has been a renaissance over the last two years in the science of these materials. This has included new n-type materials, the synthesis of true p-type materials, and the theoretical prediction and subsequent confirmation of the applicability of codoping to produce p-type ZnO. Considering that over the last 20 years much of the work on TCOs was empirical and focused on ZnO and variants of InxSn1-xO2, it is quite remarkable how this field has exploded. This may be a function of not only the need to achieve higher performance levels for these devices, but also of the increasing importance of transition-metal-based oxides in electro-optical devices. This issue of MRS Bulletin is thus well timed to provide an overview of this rapidly expanding area. Included are articles that cover the industrial perspective, new n-type materials, new p-type materials, novel deposition methods, and approaches to developing both an improved basic understanding of the materials themselves as well as models capable of predicting performance limits.

Transparent Electrodes for Efficient Optoelectronics

“…Classic examples of n-type doped transparent conductors are Sn-doped In 2 O 3 (ITO), F-doped SnO 2 (FTO), doped zinc oxide (ZnO), and cadmium oxide (CdO). [4,[22][23][24][25] Conductive polymers such as poly (3,4-ethylenedioxythiophene) doped with polystyrene sulfonic acid (PEDOT:PSS) also partially offer both intrinsic properties. [26][27][28] A second strategy consists of dimensional engineering using conductive, but not necessarily transparent materials (e.g., metals or carbon-based materials [29] ) and their arrangement in such a way that the system conducts in one direction and is transparent in the other.…”

Inverse design approach to hole doping in ternary oxides: Enhancingp-type conductivity in cobalt oxide spinels

“…Bulk and powder samples of Zn x Co 3-x O 4 and Mg-& Ni-substituted Zn x Co 3-x O 4 were fabricated using an aqueous route, in order to mix cations at an atomic level more rapidly than can be achieved by conventional solid state processing at low temperatures. For the Zn x Co 3-x O 4 samples, stoichiometric amounts of Co nitrate hexahydrate, 99.999%, and Zn nitrate hexahydrate, 99.998% (both Alfa Aesar, Ward Hill, MA) were dissolved in de-ionized water at room temperature to yield nominal cation ratios, Co/(Zn+Co), ranging from 0.667 to 1.…”

Electronic properties of layered multicomponent wide-band-gap oxides: A combinatorial approach

“…Serving as a contact and a window layer simultaneously, TCOs are a vital part of many optoelectronic devices including solar cells, smart windows and flat panel displays, and they also find application as heating, antistatic and optical coatings, for select reviews see Refs. [1][2][3][4][5][6][7]. Multicomponent TCOs -complex oxides which contain a combination of post-transition metals, In, Zn, Ga, Cd or Sn, as well as light main-group metals such as Al or Mg -have attracted wide attention due to a possibility to manipulate the optical, electronic, and thermal properties via the chemical composition and, thus, to significantly broaden the application range of TCO materials [1,3,[6][7][8][9][10][11][12][13][14][15].…”