InP/ZnS nanocrystals for colour conversion in white light emitting diodes

Roza Shirazi

Research output: Book/ReportPh.D. thesis

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Abstract

In this work a comprehensive study of a colloidal InP/ZnS nanocrystals (NC) as the colour conversion material for white light emitting diodes (WLED) is shown. Studied nanocrystals were synthesised by wet chemistry using one pot, hot injection method. A quantum efficiency (QE) of photoluminescence joined with a time resolved photoluminescence (TRPL) measurements of NCs covering the visible light spectrum range revealed a presence of a population of NCs that does not emit light upon photon absorption and it is significantly higher for a larger particles. By modifying local density of optical states, radiative and non-radiative recombination rates were determined and QE of 63% for the population of NCs that emit light was derived. A search for source of exciton losses in bright nanocrystals temperature resolved TRPL was studied and it revealed carrier trapping most likely at core-shell interface as well as at the surface and which competes with bright and dark exciton states. A presence of long-lived dark excitons and trapped charges lead to strong Auger recombination at high (relative to the trapping times) excitation. A colour conversion efficiency of the nanocrystals upon light absorption and in a process of resonant energy transfer varied from 0.03 to 0.05% and from 0.6 to 4.8 %, respectively. Finally, an analysis of luminous efficacy of radiation of hybrid WLEDs revealed that it is close to the theoretically predicted ~ 300 lm/W for phosphor based WLED.
Original languageEnglish
Place of PublicationKgs. Lyngby
PublisherTechnical University of Denmark
Number of pages151
Publication statusPublished - 2013

Cite this

Shirazi, R. (2013). InP/ZnS nanocrystals for colour conversion in white light emitting diodes. Kgs. Lyngby: Technical University of Denmark.
Shirazi, Roza. / InP/ZnS nanocrystals for colour conversion in white light emitting diodes. Kgs. Lyngby : Technical University of Denmark, 2013. 151 p.
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title = "InP/ZnS nanocrystals for colour conversion in white light emitting diodes",
abstract = "In this work a comprehensive study of a colloidal InP/ZnS nanocrystals (NC) as the colour conversion material for white light emitting diodes (WLED) is shown. Studied nanocrystals were synthesised by wet chemistry using one pot, hot injection method. A quantum efficiency (QE) of photoluminescence joined with a time resolved photoluminescence (TRPL) measurements of NCs covering the visible light spectrum range revealed a presence of a population of NCs that does not emit light upon photon absorption and it is significantly higher for a larger particles. By modifying local density of optical states, radiative and non-radiative recombination rates were determined and QE of 63{\%} for the population of NCs that emit light was derived. A search for source of exciton losses in bright nanocrystals temperature resolved TRPL was studied and it revealed carrier trapping most likely at core-shell interface as well as at the surface and which competes with bright and dark exciton states. A presence of long-lived dark excitons and trapped charges lead to strong Auger recombination at high (relative to the trapping times) excitation. A colour conversion efficiency of the nanocrystals upon light absorption and in a process of resonant energy transfer varied from 0.03 to 0.05{\%} and from 0.6 to 4.8 {\%}, respectively. Finally, an analysis of luminous efficacy of radiation of hybrid WLEDs revealed that it is close to the theoretically predicted ~ 300 lm/W for phosphor based WLED.",
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Shirazi, R 2013, InP/ZnS nanocrystals for colour conversion in white light emitting diodes. Technical University of Denmark, Kgs. Lyngby.

InP/ZnS nanocrystals for colour conversion in white light emitting diodes. / Shirazi, Roza.

Kgs. Lyngby : Technical University of Denmark, 2013. 151 p.

Research output: Book/ReportPh.D. thesis

TY - BOOK

T1 - InP/ZnS nanocrystals for colour conversion in white light emitting diodes

AU - Shirazi, Roza

PY - 2013

Y1 - 2013

N2 - In this work a comprehensive study of a colloidal InP/ZnS nanocrystals (NC) as the colour conversion material for white light emitting diodes (WLED) is shown. Studied nanocrystals were synthesised by wet chemistry using one pot, hot injection method. A quantum efficiency (QE) of photoluminescence joined with a time resolved photoluminescence (TRPL) measurements of NCs covering the visible light spectrum range revealed a presence of a population of NCs that does not emit light upon photon absorption and it is significantly higher for a larger particles. By modifying local density of optical states, radiative and non-radiative recombination rates were determined and QE of 63% for the population of NCs that emit light was derived. A search for source of exciton losses in bright nanocrystals temperature resolved TRPL was studied and it revealed carrier trapping most likely at core-shell interface as well as at the surface and which competes with bright and dark exciton states. A presence of long-lived dark excitons and trapped charges lead to strong Auger recombination at high (relative to the trapping times) excitation. A colour conversion efficiency of the nanocrystals upon light absorption and in a process of resonant energy transfer varied from 0.03 to 0.05% and from 0.6 to 4.8 %, respectively. Finally, an analysis of luminous efficacy of radiation of hybrid WLEDs revealed that it is close to the theoretically predicted ~ 300 lm/W for phosphor based WLED.

AB - In this work a comprehensive study of a colloidal InP/ZnS nanocrystals (NC) as the colour conversion material for white light emitting diodes (WLED) is shown. Studied nanocrystals were synthesised by wet chemistry using one pot, hot injection method. A quantum efficiency (QE) of photoluminescence joined with a time resolved photoluminescence (TRPL) measurements of NCs covering the visible light spectrum range revealed a presence of a population of NCs that does not emit light upon photon absorption and it is significantly higher for a larger particles. By modifying local density of optical states, radiative and non-radiative recombination rates were determined and QE of 63% for the population of NCs that emit light was derived. A search for source of exciton losses in bright nanocrystals temperature resolved TRPL was studied and it revealed carrier trapping most likely at core-shell interface as well as at the surface and which competes with bright and dark exciton states. A presence of long-lived dark excitons and trapped charges lead to strong Auger recombination at high (relative to the trapping times) excitation. A colour conversion efficiency of the nanocrystals upon light absorption and in a process of resonant energy transfer varied from 0.03 to 0.05% and from 0.6 to 4.8 %, respectively. Finally, an analysis of luminous efficacy of radiation of hybrid WLEDs revealed that it is close to the theoretically predicted ~ 300 lm/W for phosphor based WLED.

M3 - Ph.D. thesis

BT - InP/ZnS nanocrystals for colour conversion in white light emitting diodes

PB - Technical University of Denmark

CY - Kgs. Lyngby

ER -

Shirazi R. InP/ZnS nanocrystals for colour conversion in white light emitting diodes. Kgs. Lyngby: Technical University of Denmark, 2013. 151 p.