Novel Phosphors for Luminescence Conversion Intern: Ian Chapman - PowerPoint PPT Presentation

Novel Phosphors for Luminescence Conversion • Intern: Ian Chapman (ME Major, SBCC) • Mentor: Ronan Le Toquin • Faculty Advisor: Tony Cheetham UCSB Materials Lab, Summer 2004 Project Funding: Solid State Lighting Device and Display Center

Phosphor Applications • Luminescence Conversion – Fluorescent Lighting – Solid State White LEDs • Photon / Electron Detection – TV Screens – CERN’s L3 Experiment

Project Overview • Objective: – Synthesize novel phosphors for luminescence down-conversion (from Blue/UV to yellow). • Motivation: – Improve efficiency & lifetime of solid state lighting.

Luminescent Down-Conversion e - Internal Energy e - Increasing Energy Excitation Energy Emission Energy e - E λ = hc Excitation / Relaxation Energy Diagram

Luminescence Conversion White LED Luminescence Converter (Phosphor) Blue ~ 480 nm Blue Light + Violet / UV Light + Yellow Light White Light GaN / SiC Chip ~ 580 nm Adapted from: http://science.howstuffworks.com/light6.htm Adapted from: Schlotter, Schmidt, and Schneider, Luminescence conversion of blue light emitting diodes, Appl. Phys. A 64, 417-418 (1997)

Research Methods • Approach: – Design new applicable phosphor materials. • Alter existing PL materials. • Create entirely new phosphors. – Synthesis • Sol-Gel • Solid State – Characterization • XRD • PL

Langbeinite Structure Ce Composition: K 2 YZr(PO 4 ) 3 Space Group: P 2 1 3 Crystal System: Cubic Cell Parameters: 10.3345(8) (x10 -10 m)

(Why) Sol-Gel Synthesis M(NO 3 ) 3 + H 2 O H 2 O Add H 3 PO 4 Drying Crystallization Sol Gel Xerogel Ceramic Powder Mill, Heat to 700 o C M(NO 3 ) 3 + H 3 PO 4 MPO 4 + 3H 2 O Adapted from: Brinker and Scherer, Sol Gel Science , Academic Press (1990)

Powder X-Ray Diffraction http://www.mrl.ucsb.edu/mrl/centralfacilities/xray/xray-basics/Xray-basics.html#x1 Scale: λ Cu = 1.54 Å http://www.mrl.ucsb.edu/mrl/centralfacilities/xray/xray-basics/Xray-basics.html#x1

Langbeinite: K 2 YZr(PO 4 ) 3 , 2% Ce Doped Sintag X2 Theta-Theta Diffractometer

Luminescence Spectrometer YAG:Ce 450 (Standard) Sample B 400 350 300 Sample A Intensity (cts) 250 200 150 100 Excitation: Samples A&B – 380nm 50 YAG:Ce – 460nm 0 350 400 450 500 550 600 650 700 750 Wavelength (nm)

Future Research • High efficiency solid state lighting. • Improved synthesis methods. • Materials integration.

Acknowledgements Acknowledgements http://science.howstuffworks.co http://science.howstuffworks.co • MRL: • MRL: Cheetham Cheetham Group, Joe Doyle Group, Joe Doyle m/light6.htm m/light6.htm • INSET: Trevor • INSET: Trevor Hirst Hirst, Nick Arnold, Mike , Nick Arnold, Mike Northen Northen • SBCC: Dr. Young, Don Ion • SBCC: Dr. Young, Don Ion 450 400 350 300 Intensity (cts) 250 200 150 100 50 0 350 400 450 500 550 600 650 700 750 Wavelength (nm) Adapted from: Schlotter, Schmidt, and Schneider, Luminescence conversion of blue light emitting Adapted from: Brinker and Scherer, Sol Gel Science , Academic Press (1990) diodes, Appl. Phys. A 64, 417-418 (1997)

Relative Efficiencies / Lifetimes: 100 W Incandescent Bulb (~800 h): 17 lu / W Fluorescent Tubes (~10,000 h): 50-70 lu / W White LUCO LED (~100,000 h): 40-50 lu / W (Nichia) 65-74 lu / W (Cree) White LED Spectra Sol-Gel O O OH P O M M OH O O OH M O P O Haaheim , A History of Solid State White Lighting , UCSB (2002)