[Paper Review] Review of wide band gap chalcogenide semiconductors

Rachel Woods‐Robinson, Yanbing Han+5 more|arXiv (Cornell University)|Oct 17, 2019

Chalcogenide Semiconductor Thin Films4 citations

TL;DR

This review synthesizes current knowledge on wide band gap chalcogenide semiconductors, emphasizing their role as transparent conductors and optoelectronic materials. It outlines design principles, reviews key classes like II-VI binaries, chalcopyrites, and 2D materials, and highlights computational predictions and applications in photovoltaics, transistors, and diodes, aiming to guide future innovation in transparent electronics.

ABSTRACT

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.

Motivation & Objective

• To identify and systematize the design principles for high-performance wide band gap chalcogenide transparent conductors.
• To review the progress and properties of major chalcogenide families, including II-VI binaries, chalcopyrites, sulvanites, and 2D materials.
• To examine the role of computational predictions in identifying new candidate materials within the chalcogenide family.
• To evaluate the applications of wide band gap chalcogenides in photovoltaic, photoelectrochemical, and transparent electronic devices.
• To inspire future research by outlining promising directions in chalcogenide-based transparent conductors and optoelectronic materials.

Proposed method

• Systematic categorization of wide band gap chalcogenide semiconductors based on crystal structure and composition, including II-VI binaries, CuMCh2 chalcopyrites, Cu3MCh4 sulvanites, and mixed-anion layered materials.
• Analysis of experimental and theoretical data on optical and electrical properties, such as band gap, carrier mobility, and ionization potential.
• Use of computational methods to predict new chalcogenide candidates with favorable electronic and optical characteristics.
• Evaluation of material performance metrics including transparency, electrical conductivity, and p-type doping efficiency.
• Integration of findings across material classes to identify trends in band alignment, defect tolerance, and device compatibility.
• Review of device-level applications, focusing on how chalcogenides function as active or passive layers in solar cells, transistors, and diodes.

Experimental results

Research questions

• RQ1 What are the key materials design parameters that enable high-performance transparent conductors in wide band gap chalcogenides?
• RQ2 How do the electronic and optical properties of II-VI binary chalcogenides compare to those of chalcopyrites and sulvanites?
• RQ3 To what extent can computational modeling predict novel wide band gap chalcogenide materials with desirable optoelectronic properties?
• RQ4 What are the dominant mechanisms enabling p-type doping and high hole mobility in chalcogenide semiconductors?
• RQ5 In which optoelectronic devices do wide band gap chalcogenides show the most promising performance as active or transparent conductive layers?

Key findings

• Wide band gap chalcogenides exhibit high optical transparency and controllable electrical conductivity, making them suitable for transparent conductive applications.
• II-VI binary chalcogenides, chalcopyrites (e.g., CuInSe2), and sulvanites (e.g., Cu3BiS3) demonstrate favorable band alignments and high valence band positions for p-type behavior.
• Chalcogenide materials such as CdTe are already successfully used in commercial photovoltaic devices, showing high efficiency in solar cells.
• Computational studies predict new chalcogenide candidates with band gaps exceeding 2 eV and favorable carrier transport properties.
• Layered materials like CuMCh(O,F) and 2D chalcogenides show promise for flexible and transparent electronics due to their tunable band structures.
• Chalcogenide-based transparent transistors and diodes have demonstrated performance comparable to oxide-based devices, with potential for lower processing temperatures and enhanced stability.