Eu$^{2+}$: a suitable substituent for Pb$^{2+}$ in CsPbX$_3$ perovskite nanocrystals?

TL;DR

This paper explores Eu$^{2+}$ as a non-toxic substitute for Pb$^{2+}$ in CsPbX$_3$ perovskite nanocrystals, demonstrating synthesis, structural properties, and promising optical performance for optoelectronic applications.

Contribution

It introduces a new synthesis method for Eu$^{2+}$-doped perovskite nanocrystals and characterizes their structural and optical properties, highlighting their potential as lead-free blue emitters.

Findings

CsEuBr$_3$ NCs emit bright blue light at 413nm

Photoluminescence quantum yield of 39% at room temperature

Long-term stability of optical properties

Abstract

Eu$^{2+}$ is used to replace toxic Pb$^{2+}$ in metal halide perovskite nanocrystals (NCs). The synthesis implies injection of cesium oleate into a solution of europium (II) bromide at an experimentally determined optimum temperature of 130C and a reaction time of 60s. Structural analysis indicates the formation of spherical CsEuBr$_3$ nanoparticles with a mean size of 43nm. Using EuI$_2$ instead of EuBr$_2$ leads to the formation of 18nm CsI nanoparticles, while EuCl$_2$ does not show any reaction with cesium oleate forming 80nm EuCl2 nanoparticles. The obtained CsEuBr3 NCs exhibit bright blue emission at 413nm (FWHM 30 nm) with a room temperature photoluminescence quantum yield of 39%. The emission originates from the Laporte-allowed 4f7-4f65d1 transition of Eu$^{2+}$ and shows a PL decay time of 263ns. The long-term stability of the optical properties is observed, making inorganic lead-free CsEuBr$_3$ NCs promising deep blue emitters for optoelectronics.