Efforts to develop ‘transparent’ electronics aren’t new, but difficulty identifying dopants that can be used to produce transparent conductors has slowed progress. The main problem is a shortage of suitable high-performance P-Type (positively charged carriers) conductors in which the implanted impurity has one electron too few. Recently, researchers at the University of Basel used the “Piz Daint” supercomputer to simulate possible dopants behavior and identify promising candidates.

As explained in the abstract of their paper[i]: “The advancement of transparent electronics, one of the most anticipated technological developments for the future, is currently inhibited by a shortage of high-performance p-type semiconductors. Recent demonstration of tin monoxide as a successful transparent p-type thin-film transistor and the discovery of its potential for ambipolar doping, suggests that tin monoxide—an environmentally friendly earth-abundant material—could offer a solution to this challenge.”

A brief report on the work, posted this week on the CSCS (Swiss Supercomputing Center) website, notes that identifying suitable impurities in the periodic table, often involves years of expensive laboratory experimentation. “Researchers are attempting to speed up this process by using computer simulations. They use these to calculate the most promising candidates on the basis of physical laws that describe the interaction between the impurity and the material of the conductor. Potential candidates can then be tested in the laboratory in a targeted manner,” according to the article written by Simone Ulmer.

In their paper the researchers write, “Substitutional doping with the family of alkali metals was identified as a successful route to increase the concentration of acceptors in SnO and over ten shallow donors, which, to the best of our knowledge, have not been previously contemplated, were discovered. This work presents a detailed analysis of the most promising n-/p-type dopants—offering new insights into the design of an ambipolar SnO. If synthesized successfully, such a doped ambipolar oxide could open new avenues for many transparent technologies.”

Using simulation, the researchers identified five alkali metals (lithium, sodium, potassium, rubidium and caesium) that could be introduced into tin monoxide in order to enable high-performance and transparent P-Type semiconductors. They also identified 13 elements suitable for doping with N-Type charge carriers in tin monoxide. “If these elements can be successfully introduced into tin monoxide and the desired semiconductor can be produced, this would open new avenues for a range of transparent technologies,” says José A. Flores-Livas, one of the researchers involved in the work, in the article.

Link to article by Ulmer, https://www.cscs.ch/science/chemistry-materials/transparent-electronics-research-gains-momentum/

[i]Towards bipolar tin monoxide: Revealing unexplored dopants, https://journals.aps.org/prmaterials/abstract/10.1103/PhysRevMaterials.2.104604