Plasmonic-Enhanced Luminescence Characteristics of Microscale Phosphor Layers on a ZnO Nanorod-Arrayed Glass Substrate.

We present a planar luminescent layer for glare-free, long-lifespan white light-emitting diodes (LEDs), with attractive light outputs. The novel and facile remote phosphor approach proposed in this work enhances luminescence properties by combining a waveguiding ZnO-based nanostructure with plasmonic Au nanoparticles. The system comprised a microscale yellow phosphor layer that is applied by simple printing onto an Au nanoparticle-dispersed ZnO nanorod array. This architecture resulted in a considerable enhancement in luminous efficacy of approximately 18% because of the combination of waveguide effects from the nanorod structure and plasmonic effects from the Au nanoparticles. Performance was optimized according to the length of the Zn nanorods and the concentration of Au. An optimal efficiency of ∼84.26 lm/W for a silicate phosphor-converted LED was achieved using long ZnO nanorods and an Au concentration of 12.5 ppm. The finite-difference time-domain method was successfully used to verify the luminous efficacy improvements in the Au nanoparticle-intervened nanostructures via the waveguiding and plasmonic effects.

Micro-scale roughening of glass substrates using carbon nanotube-driven templates for enhancements in white luminescence characteristics.

A novel way of roughening the surface of a glass substrate using a carbon nanotube-driven template is introduced to enhance the white luminescence characteristics of a printed (Ba,Sr,Ca)2SiO4:Eu2+ yellow silicate phosphor layer. The distribution of closed pores in the template layer induces selective etching and micro-scale roughening. As a result, a substantial improvement of ∼22.5% in the luminous efficacy was achieved when both sides of the substrate were roughened. This is attributed to the reductions of both the total internal reflection of rays at the glass-air interface and the specular reflection at the phosphor-glass interface.

UV-curable silicate phosphor planar films printed on glass substrate for white light-emitting diodes.

We suggest a simple way of forming a nonconventional remote phosphor layer for white light-emitting diodes. A printing technology using a paste consisting of yellow (Ba,Sr,Ca)(2)SiO(4):Eu(2+) silicate phosphor and ultraviolet (UV)-curable polymer is applied to form solid planar films on a common soda lime silicate glass substrate through UV radiation. Relative content of the phosphor was adjusted for the best dispersion of the phosphor particles in the polymer matrix with better emission and luminescence performance. As a result, the 70 wt. % phosphor-embedded film has a luminous efficacy of ∼70.1 lm/W at 200 mA.

Long-term stable, low-temperature remote silicate phosphor thick films printed on a glass substrate.

A critical step in providing better phosphor solution for white light emitting diode (LED) is to utilize inexpensive silicate phosphors with strong thermal stability. Here, we demonstrate yellow silicate phosphor-embedded glass thick films with a high luminous efficacy of ∼32 lm/W at 200 mA as a nonconventional remote-phosphor approach. The simple screen-printing process of a paste consisting of (Ba,Sr,Ca)2SiO4:Eu²âº phosphor and a low softening point glass creates a planar remote structure on a regular soda lime silicate glass with controllable film thickness and location (top vs bottom) of the phosphor layer. The glass matrix provides promising densification and adhesion with the substrate at the optimal low temperature of 410 °C, with the long-term stability in luminous efficacy over 500 h of operation. The proposed phosphor structure has important implications to overcome current limitations as phosphors.