Oriented Electrophoretic Deposition of GdOCl Nanoplatelets

Abstract

Electrophoretic deposition has emerged as a versatile and precisely tunable approach for the rapid deposition of conformal thin films of colloidal nanocrystals. The electrophoretic deposition of phosphor particles has assumed special significance in recent years as a commercially viable means toward the fabrication of large-area, ultrathin high-resolution emissive display screens. Here, we demonstrate that the anisotropic shape of colloidal ligand-passivated GdOCl nanoplatelets enables their assembly with remarkable substrate alignment and a high packing density upon electrophoretic deposition. GdOCl nanocrystals are promising candidates for phosphor applications given their low maximum phonon cutoff energy, robust chemical stability over prolonged periods of operation, and ability to promote efficacious phonon energy transfer to dopant ions. Potentiostatic deposition of GdOCl nanoplatelets from cyclohexane dispersions allows the deposition of individual nanoplatelets with their basal planes parallel to the electrode surface. Tuning the applied voltage and solution concentration allows control of film thickness, ranging up to several tens of micrometers. The high degree of particle alignment is attributed to anisotropic charge distribution and entrainment within electroosmotic flows established in the vicinity of the electrode surface. The oriented high-particle-density GdOCl nanoplatelet thin films are possible candidates for phosphor applications, which is illustrated by the green emission from a Tb-doped GdOCl thin film on indium tin oxide (ITO)-coated glass.