Comprehensive review of p- and n-type transparent conducting materials

Many optoelectronic devices, including solar cells, touch screens and LEDs, use transparent conducting materials(TCMs), which combine high electrical conductivity and high visible light optical transmission. However, the physical properties of TCMs remain poorly understood.

Xuefen Cai and Su-Huai Wei summarize what is known about the band structure of TCMs, which is an essential physical property for the future development of these materials.

In their review of TCMs, the authors discuss doping control and methods to achieve high conductivity and transparency in n-type TCMs. In the past two decades, significant research has gone into designing p-type TCMs. The authors also review issues with these TCMs, including why the combination of high conductivity and transparency is difficult to produce.

“So far, all the trademark TCMs are n-type. The lack of p-type TCMs impedes the design flexibility of optoelectronic devices,” said Wei. “In this perspective, one can not only find the generalized criteria for being a good n-type TCM, but also can find possible approaches to realizing the p-type TCMs, thus gaining and deepening their understanding on the fascinating feature of the TCMs.”

Possible future designs that could modify band structures for these TCMs are also presented. The authors hope the perspective can provide inspiration to further research on the physical properties of TCMs that could lead to alternative design principles for both p- and n-types.

“We hope multiple physical concepts within this paper can be used for these goals and expanded for studying the electronic and defect properties of other semiconductors apart from TCM materials,” Wei said.

Source: “Perspective on the band structure engineering and doping control of transparent conducting materials,” by Xuefen Cai and Su-Huai Wei, Applied Physics Letters (2021). The article can be accessed at https://doi.org/10.1063/5.0058450 .