Engineering the optical properties of Cu doped CeO2 NCs for application in white LED

Abstract

Cerium dioxide (ceria, CeO2) with wide band gap (3.6 eV) is optically transparent for visible light and efficiently luminescent in the UV-range. Here, we have investigated the effect of Cu dopant ions on the structural and optical properties of Ce1-xCuxO2; (0.00 ≤ x ≤ 0.20) nanocrystals (NCs) synthesized via co-precipitation technique. XRD results confirmed the successful incorporation of Cu ions into CeO2 single-phase cubic system. The decrease in the crystallite sizes (13 - 4 nm) as the Cu content increase indicates towards the decrease in the crystal quality and introduction of additional lattice defects. The concentration of oxygen deficiency (δ) and the reduction in the oxygen valency (CeO2-δ) have been evaluated quantitatively using Raman spectroscopy. The possible defects, assessed via Photoluminescence (PL) emission spectra, generate profound energy bands localized in the forbidden band region, which causes a lowering in the UV emission efficiency and narrowing the band gap energy from 3.7 eV for pure CeO2 to 3.1 eV for 20% Cu doped sample. The green PL emission band at ~520 nm (2.39 eV) is attributed to electronic decay from conduction band (CB) to donor band of oxygen vacancy (Ov), while the blue band at ~ 420 nm (2.9 eV) is due to electronic transition from CB to accepter band formed by ceria vacancies (VCe2−). The values of chromaticity coordinates and illuminating engineering parameters such as color rendering index (CRI) and correlated color temperature (CCT) of the studied samples predict their possible use in white light-emitting diode (LED).