Composite phosphors based on coating porous substrates

Abstract

A composite material is provided including a phosphor material of at least one of among hafnium oxide, niobium oxide, tantalum oxide or zirconium oxide as a conformal coating on a porous substrate, the composite characterized as exhibiting photoluminescence at room temperature. Also provided is a composite material including a phosphor material of at least one of among hafnium oxide, niobium oxide, tantalum oxide, zinc oxide or zirconium oxide as a conformal coating on a porous substrate, the composite characterized as exhibiting photoluminescence at room temperature and as having a broad emission spectrum having a width at ½ maximum greater than 80 nm.

Description

RELATED APPLICATIONS[0001]This application claims the benefit of U.S. Provisional Application Ser. No. 61 / 063,154 entitled “Composite Phosphors Based on Coating Porous Substrates,” filed Jan. 30, 2008, and U.S. Provisional Application Ser. No. 61 / 063,153 entitled “Polymer-Assisted Deposition of Conformal Films on Porous Materials,” both hereby incorporated by reference.STATEMENT REGARDING FEDERAL RIGHTS[0002]This invention was made with government support under Contract No. DE-AC52-06NA25396 awarded by the U.S. Department of Energy. The government has certain rights in the invention.FIELD OF THE INVENTION[0003]The present invention relates to a new series of metal oxide phosphors having a broad emission in the visible light region. In particular these phosphors can be deposited onto silica inverse opal structures or silica-based zeolites. The phosphors can be deposited as films by a polymer assisted deposition technique and can result in a luminescent composite material.BACKGROUND O...

AI Technical Summary

Benefits of technology

[0018]The resulting coated porous structure has observable PL at room temperature and maintains porosity which may be subsequently filled with a liquid, gel, or solid. Filling the cavities with materials of refractive index that match the substrates refractive index can lead to enhanced light output which is important for many applications.

Problems solved by technology

Phosphors are an integral part of any LED, and unfortunately contribute significantly to efficiency losses.

The loss mechanisms include fundamental losses innate to the phosphor conversion material (nonradiative decay paths that lead to reduced quantum yields) and reduced extraction efficiency.

One of the major obstacles in the development of high efficiency systems is loss due to wave guiding when thin film phosphors are used.

Nanoporous structures offer great potential, but they are very difficult to coat.

All of these structures have high surface areas but the nanometer scale porosity with openings or cavities less than about 1000 nm make them very difficult to coat by traditional line-of-site techniques.

It is not possible to make PCs from just any material, which limits their potential properties.

Coating is one way to add functionality, but traditional techniques such as pulsed laser deposition (“PLD”) and chemical vapor deposition (“CVD”) cannot coat the complex porous structures.

ALD is limited in that thicker coatings require many steps and only single component coatings can be readily applied.

However, these crystals have a scintillation decay which is not very fast.

The crystals of the BGO family have high decay time constants, which limit the use of these crystals to low count rates.

However these crystals are very heterogeneous and have very high melting points (about 2200 degrees Celsius).

While thin film scintillators have limited utility in applications where energy resolution is needed in radiation detection, they have major applications in imaging systems such as X-ray imaging device.

One of the prime difficulties in these systems is the gamma-ray rejection characteristics of the system.

In addition, many of the detector materials are air and water sensitive or the scintillators employ heavy elements that limit gamma-ray rejection or have slow response times thanks to the long relaxation times. Scintillators have the added complication that often single crystals are required to avoid light loss, making it difficult to add large amounts of boron or lithium to increase the neutron cross-section absorption.

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