The race to replace tin-doped indium oxide: which material will win?

The search for materials that can replace tin-doped indium oxide (ITO) as the leading transparent conductive electrode (TCE) has intensified significantly in the past few years, motivated by the ever-increasing price of indium. Materials such as carbon nanotube (CNT) films, graphene films, metal nanowire gratings, and random networks have been at the forefront of research in this direction. A paper by Wu et al. in this issue discusses the use of solution-processed graphene as the TCE in organic light-emitting devices. Advantages such as large-scale fabrication at relatively less expense, compatibility with flexible substrates, and improving performance have significantly contributed to their case as potential candidates for TCEs. Demonstrations of various display and photovoltaic devices using TCEs made of these materials, with performances rivaling those employing ITO, have provided the research community with encouragement to explore new materials and to address the associated scientific and technological challenges.