Anomalous Workfunction Anisotropy in Ternary Acetylides

TL;DR

This study reveals significant workfunction anisotropy in ternary acetylides, with potential applications in electron emission and solar energy devices, driven by the orientation of polymeric subunits affecting surface properties.

Contribution

It demonstrates large workfunction anisotropy in ternary acetylides and predicts low workfunction surfaces, expanding their potential for electronic and optoelectronic applications.

Findings

Workfunction differences exceed 2 eV depending on surface orientation.

Conversion of Cs2Te to Cs2TeC2 significantly reduces workfunction.

Predicted low workfunction surfaces suitable for various electronic devices.

Abstract

Anomalous anisotropy of workfunction values in ternary alkali metal transition metal acetylides is reported. Workfunction values of some characteristic surfaces in these emerging semiconducting materials may differ by more than $\approx$ 2 eV as predicted by Density Functional Theory calculations. This large anisotropy is a consequence of the relative orientation of rod-like [MC$_{2}$]$_{\infty}$ negatively charged polymeric subunits and the surfaces, with M being a transition metal or metalloid element and C$_{2}$ refers to the acetylide ion C$_{2}^{2-}$, with the rods embedded into an alkali cation matrix. It is shown that the conversion of the seasoned Cs$_{2}$Te photo-emissive material to ternary acetylide Cs$_{2}$TeC$_{2}$ results in substantial reduction of its $\approx$ 3 eV workfunction down to 1.71-2.44 eV on the Cs$_{2}$TeC$_{2}$(010) surface while its high quantum yield is preserved. Similar low workfunction values are predicted for other ternary acetylides as well, allowing for a broad range of applications from improved electron- and light-sources to solar cells, field emission displays, detectors and scanners.