ISO 20351:2017
(Main)Fine ceramics (advanced ceramics, advanced technical ceramics) — Absolute measurement of internal quantum efficiency of phosphors for white light emitting diodes using an integrating sphere
Fine ceramics (advanced ceramics, advanced technical ceramics) — Absolute measurement of internal quantum efficiency of phosphors for white light emitting diodes using an integrating sphere
ISO 20351:2017 specifies a method of absolute measurement (using an integrating sphere) of internal quantum efficiency of phosphor powders which are excited by UV or blue light and emit visible light, and which are used for white light-emitting diodes (LEDs). ISO 20351:2017 can be adopted for the measurement of phosphors used in non-white LEDs, for example, green, orange, pink or purple LEDs.
Céramiques fines (céramiques avancées, céramiques techniques avancées) — Mesurage absolu du rendement quantique interne des luminophores des diodes électroluminescentes blanches en utilisant une sphère intégrante
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INTERNATIONAL ISO
STANDARD 20351
First edition
2017-09
Fine ceramics (advanced ceramics,
advanced technical ceramics) —
Absolute measurement of internal
quantum efficiency of phosphors for
white light emitting diodes using an
integrating sphere
Céramiques fines (céramiques avancées, céramiques techniques
avancées) — Mesurage absolu du rendement quantique interne des
luminophores des diodes électroluminescentes blanches en utilisant
une sphère intégrante
Reference number
ISO 20351:2017(E)
©
ISO 2017
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ISO 20351:2017(E)
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© ISO 2017, Published in Switzerland
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ii © ISO 2017 – All rights reserved
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ISO 20351:2017(E)
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Measuring equipment . 2
4.1 Equipment configuration . 2
4.2 Light source unit . 3
4.3 Sample unit . 3
4.3.1 Cell . 3
4.3.2 White diffuser or reference cell . 4
4.3.3 Integrating sphere . 4
4.4 Detecting unit . 4
4.4.1 Directing optics . 4
4.4.2 Spectrometer and detector . 4
4.4.3 Amplifier . 4
4.5 Signal and data processing unit . 4
5 Calibration, checking and maintenance of measuring equipment .5
5.1 General . 5
5.2 Wavelength calibration of light source unit . 5
5.3 Cells and cover glasses . 5
5.4 Integrating sphere walls and white diffusers . 5
5.5 Wavelength calibration of detecting unit . 5
5.6 Spectral responsivity correction . 5
6 Samples . 5
6.1 Storage and pre-processing . 5
6.2 Filling cells with samples . 5
7 Measurement methods . 6
7.1 Measurement environment. 6
7.2 Light spectrum without phosphor sample . 6
7.3 Light spectrum with phosphor sample . 6
8 Calculations. 6
8.1 Conversion to photon-number-based spectra . 6
8.2 Photoluminescence spectrum . 7
8.2.1 General. 7
8.2.2 Method 1 . 7
8.2.3 Method 2 . 7
8.3 Internal quantum efficiency . 7
8.3.1 Relative number of absorbed photons . 7
8.3.2 Relative number of photoluminescent photons. 8
8.3.3 Internal quantum efficiency . 8
9 Report . 8
Bibliography .10
© ISO 2017 – All rights reserved iii
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ISO 20351:2017(E)
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out
through ISO technical committees. Each member body interested in a subject for which a technical
committee has been established has the right to be represented on that committee. International
organizations, governmental and non-governmental, in liaison with ISO, also take part in the work.
ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of
electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular the different approval criteria needed for the
different types of ISO documents should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see www.iso.org/directives).
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of
any patent rights identified during the development of the document will be in the Introduction and/or
on the ISO list of patent declarations received (see www.iso.org/patents).
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation on the voluntary nature of standards, the meaning of ISO specific terms and
expressions related to conformity assessment, as well as information about ISO's adherence to the
World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT) see the following
URL: www.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 206, Fine ceramics.
iv © ISO 2017 – All rights reserved
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ISO 20351:2017(E)
Introduction
White light-emitting diode (LED) based solid-state lighting (SSL) has been widely used for a variety
of applications as alternatives for incandescent and fluorescent lamps. In the beginning, white LEDs
(comprising blue LEDs and yellow phosphors) became popular as backlight sources for small-size
liquid-crystal displays (LCDs) used in mobile phones and digital cameras. These were followed by white
LEDs (consisting of blue LEDs combined with green and red phosphors) applied to backlight sources
for large-area LCDs. Subsequently, LED lamps have been commercialized for general lighting, replacing
conventional luminaires and capitalizing on their advantages, such as compactness, high luminous
efficiency, high brightness below 0 °C or higher ambient temperatures, long life, and controllability of
light intensity and colour temperature.
The optical performance of a phosphor for use in a white LED is one of the most important factors
influencing the performance of the white LED. Accordingly, it is of great importance, not only for
researchers and manufacturers of phosphors for use in white LEDs but also for researchers and
manufacturers of white LED devices, to evaluate the optical properties of the phosphors in a well-
established manner. However, standard measurement methods of studying the optical properties of
luminescent powder materials commercially used for white LEDs have never been developed.
Photoluminescence quantum efficiency is one of the key parameters of phosphors for use in white LEDs
and has been measured extensively by using an integrating sphere-based absolute method. This method
was originally developed to determine the photoluminescence quantum efficiency for fluorophore-
doped organic thin films and solutions, and has also been applied to phosphor powders. However,
those who measure the quantum efficiency of phosphor materials have frequently noted that the
measured quantum efficiency may deviate beyond their tolerance level, depending on the measurement
equipment, the geometrical configuration of the integrating sphere and the arrangement of the sample
cell, even if the measurement procedure is common in principle. This document provides the absolute
measurement method of internal quantum efficiency of phosphors for use in white LEDs with reduced
deviation of measured values. In this document, measurement equipment and procedures, which can be
the sources of the deviation, are described in detail, helping those who address the high performance
phosphors for competitive SSL products to obtain the proper information on their competitiveness.
© ISO 2017 – All rights reserved v
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INTERNATIONAL STANDARD ISO 20351:2017(E)
Fine ceramics (advanced ceramics, advanced technical
ceramics) — Absolute measurement of internal quantum
efficiency of phosphors for white light emitting diodes
using an integrating sphere
1 Scope
This document specifies a method of absolute measurement (using an integrating sphere) of internal
quantum efficiency of phosphor powders which are excited by UV or blue light and emit visible light,
and which are used for white light-emitting diodes (LEDs).
This document can be adopted for the measurement of phosphors used in non-white LEDs, for example,
green, orange, pink or purple LEDs.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements of this document. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any amendments) applies.
CIE S 017/E:2011, International Lighting Vocabulary
3 Terms and definitions
For the purposes of this document, the terms and definitions given in CIE S 017/E:2011 and the
following apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at http://www.iso.org/obp
— IEC Electropedia: available at http://www.electropedia.org/
3.1
internal quantum efficiency
ratio of the number of photons emitted in free space from the phosphor to the number of excitation
light photons absorbed by the phosphor
3.2
cell
container filled with a sample or a white material such as barium sulfate
Note 1 to entry: A cell is typically a flat plate sample holder with a cylindrical hollow, a Petri dish or a rectangular
cell used in a spectrophotometer.
3.3
reference cell
cell (3.2) filled with a white powder which has a high spectral diffuse reflectance over the whole visible
spectrum (such as barium sulfate or alumina), used when measuring the excitation light spectrum
3.4
white diffuser
white plate which has a high spectral diffuse reflectance over the whole visible spectrum [suc
...
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