Phosphor-Free Electrically Driven White Light Emission from Nanometer-Thick Barium–Organic Framework Films

Abstract

Self-assembly of an environmentally friendly non-lanthanide barium-based metal–organic framework {[Ba(2,6-ndc)(H2O)2]·H2O} (1, 2,6-ndc = 2,6-naphthalenedicarboxylate) (Ba-MOF) is reported. The complex displays an intrinsic broad-band white light emission with a Commission International de I’Eclairage (CIE) index of (0.32, 0.33), and a corresponding yield of about 75%, when excited at a wavelength of 374 nm. The continuous broad band can be attributed to the inherent nature of Ba-MOF (1), i.e., interligand (π–π*) and ligand–metal charge transfer mechanisms, resulting in a white light emission. Moreover, a device is fabricated using a nanometer-scale thin film of Ba-MOF (1) as an active material and the resulting device exhibits a white electroluminescence spectrum. In comparison with the traditional two-component light-emitting diodes (LEDs), this MOF-based white light LED system has significant advantages such as its ability to function as a phosphor-free, single-component broad-band emitter, high stability, low cost, and minimal environmental footprints. Density functional theory (DFT) calculations are carried out to better comprehend the origin of this white light emission from 1. This Ba-MOF-based white light emitter has the potential for being an environmentally friendly and low-cost source for white light solid-state applications.