Bridging the p-type transparent conductive materials gap: synthesis approaches for disperse valence band materials

Abstract

Transparent conductive materials (TCMs) with high p-type conductivity and broadband transparency have remained elusive for years. Despite decades of research, no p-type material has yet been found to match the performance of n-type TCMs. If developed, the high-performance p-type TCMs would lead to significant advances in a wide range of technologies, including thin-film transistors, transparent electronics, flat screen displays, and photovoltaics. Recent insights from high-throughput computational screening have defined design principles for identifying candidate materials with low hole effective mass, also known as disperse valence band materials. Particularly, materials with mixed-anion chemistry and nonoxide materials have received attention as being promising next-generation p-type TCMs. However, experimental demonstrations of these compounds are scarce compared to the computational output. One reason for this gap is the experimental difficulty of safely and controllably sourcing elements, such as sulfur, phosphorous, and iodine for depositing these materials in thin-film form. Another important obstacle to experimental realization is air stability or stability with respect to formation of the competing oxide phases. We summarize experimental demonstrations of disperse valence band materials, including synthesis strategies and common experimental challenges. We end by outlining recommendations for synthesizing p-type TCMs still absent from the literature and highlight remaining experimental barriers to be overcome.

Latest directions in p-type transparent conductor design

“…9 Fioretti and Morales-Masis offer a perspective on disperse valence band materials for p-type applications, with an insightful discussion on some of the experimental challenges that come with moving away from oxide-based chemistries. 10 Finally, Shi et al offer a comprehensive overview of both p-and n-type wide bandgap oxide semiconductors, with a particular focus on optoelectronic devices and applications, an invaluable resource on emerging thin-film transistor devices and OLED technologies, 11 while Wang et al focus more intimately on developments in the p-type semiconductor device field. 5 The field of organic optoelectronics is a key area of research associated with TCM technology, but is often omitted from discussions where inorganic materials are present (certainly from most of the above, with the notable exception of Table 1 Optoelectronic properties of p-type TCMs from the literature.…”

Impurity Doping in Mg(OH)2 for n-Type and p-Type Conductivity Control

“…Many oxides act as TCMs, and they are known as transparent conductive oxides (TCO) [ 2 ]; In 2 O 3 and SnO 2 are the most popular materials for transparent electrodes. Sulfides and oxy-chalcogenides have also attracted attention as TCMs [ 3 ]. The majority of TCMs show n-type conductivity without intentional doping, and conductivity can be controlled relatively easily by doping with a proper donor, e.g., Sn for In 2 O 3 (ITO) and F for SnO 2 (FTO).…”

“…For ZnO, Al and Ga are known to be good shallow donors. On the other hand, a limited number of p-type TCMs are known, and it is generally difficult to enhance p-type conductivity by acceptor doping because of self-compensation, deep acceptor level, and the localized nature of holes [ 3 , 4 , 5 ].…”

Special Section Guest Editorial: Get WIRED!

“…The papers in this special section represent an overview of a very small sample of ongoing research activities led by women researchers in academia worldwide.Angela N. Fioretti from the École Polytechnique Fédérale de Lausanne in Switzerland, and Monica Morales-Masis from the University of Twente in the Netherlands have identified materials with mixed-anion chemistry and nonoxide materials as next-generation p-type transparent conducting materials (TCMs). 1 Their theoretical studies outline recommendations for synthesizing these p-type TCMs and highlight remaining experimental barriers to be overcome.Hima A. Kavuri from the University of Auckland in New Zealand and her collaborators from the MacDiarmid Institute for Advanced Materials and Nanotechnology in New Zealand have introduced a new generation of anode interlayers (AILs) for improving the efficiency and stability of organic photovoltaic devices. 2 They used poly(vinyl pyrrolidone) (PVP) as an AIL modifier to alter molybdenum trioxide (MoO 3 ) and vanadium pentoxide (V 2 O 5 ).…”

“…Angela N. Fioretti from the École Polytechnique Fédérale de Lausanne in Switzerland, and Monica Morales-Masis from the University of Twente in the Netherlands have identified materials with mixed-anion chemistry and nonoxide materials as next-generation p-type transparent conducting materials (TCMs). 1 Their theoretical studies outline recommendations for synthesizing these p-type TCMs and highlight remaining experimental barriers to be overcome.…”