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Wide band gap chalcogenide semiconductors

Wide band gap semiconductors are essential for today's electronic devices and energy applications due to their high optical transparency, as well as controllable carrier concentration and electrical conductivity. There are many categories of materials that can be defined as wide band gap semiconductors. The most intensively investigated are transparent conductive oxides (TCOs) such as ITO and IGZO used in displays, carbides and nitrides used in power electronics, as well as emerging halides (e.g. CuI) and 2D electronic materials used in various optoelectronic devices. Chalcogen-based (S, Se, Te) wide band gap semiconductors are less heavily investigated but stand out due to their propensity for p-type doping, high mobilities, high valence band positions (i.e. low ionization potentials), and broad applications in electronic devices such as CdTe solar cells. This manuscript provides a review of wide band gap chalcogenide semiconductors. First, we outline general materials design parameters of high performing transparent conductors. We proceed to summarize progress in wide band gap (Eg > 2 eV) chalcogenide materials, such as II-VI MCh binaries, CuMCh2 chalcopyrites, Cu3MCh4 sulvanites, mixed anion layered CuMCh(O,F), and 2D materials, among others, and discuss computational predictions of potential new candidates in this family, highlighting their optical and electrical properties. We finally review applications of chalcogenide wide band gap semiconductors, e.g. photovoltaic and photoelectrochemical solar cells, transparent transistors, and diodes, that employ wide band gap chalcogenides as either an active or passive layer. By examining, categorizing, and discussing prospective directions in wide band gap chalcogenides, this review aims to inspire continued research on this emerging class of transparent conductors and to enable future innovations for optoelectronic devices.