Design rule for the emission linewidth of Eu$^{2+}$-activated phosphors

TL;DR

This study presents a first-principles-based design rule for predicting the emission linewidth of Eu$^{2+}$-activated phosphors, linking linewidth to Franck-Condon energy shifts and Stokes shift, aiding the development of narrow-emission phosphors.

Contribution

It introduces a first-principles approach to determine emission linewidths in Eu$^{2+}$ phosphors based on the configuration coordinate model, highlighting the role of Franck-Condon energy shifts.

Findings

Linewidth is negligibly affected by quantum effects at working temperature.

The linewidth can be predicted from Franck-Condon energy shifts.

Large positive differences in Franck-Condon shifts lead to narrower emission linewidths.

Abstract

We study from first principles the emission linewidth of Eu$^{2+}$-doped LED phosphors. Based on the one-dimensional configuration coordinate model, an analysis of first principles data obtained for fifteen compounds show that, at working temperature, the linewidth of Eu$^{2+}$ emission band in solids is negligibly affected by quantum effects, and can be extracted from the Franck-Condon energy shifts. For a fixed Stokes shift, the difference of Franck-Condon energy shifts in the excited and ground states is the key factor for the FWHM determination. Narrow emission Eu$^{2+}$-doped LED phosphors are expected for the case with large positive value of such difference.