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Excitation dependent quenching of luminescence in LED phosphors
Author(s) -
Shchekin Oleg B.,
Schmidt Peter J.,
Jin Fahong,
Lawrence Nate,
Vampola Kenneth J.,
Bechtel Helmut,
Chamberlin Danielle R.,
MuellerMach Regina,
Mueller Gerd O.
Publication year - 2016
Publication title -
physica status solidi (rrl) – rapid research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.786
H-Index - 68
eISSN - 1862-6270
pISSN - 1862-6254
DOI - 10.1002/pssr.201600006
Subject(s) - phosphor , voltage droop , light emitting diode , optoelectronics , brightness , luminescence , quantum efficiency , materials science , quenching (fluorescence) , excitation , absorption (acoustics) , diode , excited state , optics , power (physics) , physics , electrical engineering , fluorescence , atomic physics , engineering , thermodynamics , composite material , voltage divider
Droop, the decrease of efficiency with increased power density, became a major topic with InGaN LEDs, after its introduction in 2007. This paper provides insight into droop in localized center luminescence phosphors, exemplified here by Eu 2+ doped materials. This topic is of increasing importance, as high brightness blue LEDs have reached outputs >1 W/mm 2 . The nonlinearities in phosphor quantum efficiency result in drive‐dependent color point shift and reduction of overall efficiency of phosphor converted white LEDs which utilize Eu 2+ activated phosphors. The efficiency quenching can be traced back to two processes, well‐known in laser physics, excited state absorption or/and cross relaxation by Foerster/Dexter transfer. Both processes lead to reduction in phosphor efficiency, but they can be differentiated. Understanding the root cause of efficiency quenching opens ways to minimize the practical consequences. (© 2016 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim)