Semiconductor devices - Part 5-8: Optoelectronic devices - Light emitting diodes - Test method of optoelectronic efficiencies of light emitting diodes

IEC 60747-5-8:2019 specifies the terminology and the measuring methods of various efficiencies of single light emitting diode (LED) chips or packages without phosphor. White LEDs for lighting applications are out of the scope of this part of IEC 60747. The efficiencies whose measuring methods are defined in this part are the power efficiency (PE), the external quantum efficiency (EQE), the voltage efficiency (VE), and the light extraction efficiency (LEE). To measure the LEE, the measurement data of the internal quantum efficiency (IQE) is used, whose measuring method is discussed in IEC 60747-5-9 and IEC 60747-5-10. The injection efficiency (IE) and the radiative efficiency (RE) are given definitions only.

Dispositifs à semiconducteurs - Partie 5-8 : Dispositifs optoélectroniques - Diodes électroluminescentes - Méthode d’essai des efficacités optoélectroniques des diodes électroluminescentes

L’IEC 60747-5-8:2019 spécifie la terminologie et les méthodes de mesure des efficacités des puces ou des boîtiers de diodes électroluminescentes (DEL) sans phosphore. Les DEL blanches destinées aux applications d’éclairage sont exclues de la présente partie de l’IEC 60747. Les méthodes de mesure de l’efficacité énergétique (PE), de l’efficacité quantique externe (EQE), de l’efficacité de tension (VE) et de l’efficacité d’extraction de lumière (LEE) sont définies dans la présente partie. Pour mesurer le LEE, les données de mesure de l’efficacité quantique externe (IQE) sont utilisées, dont la méthode de mesure est discutée dans l'IEC 60747-5-9 et l'IEC 60747-5-10. Concernant l’efficacité d’injection (IE) et l’efficacité radiative (RE), seules leurs définitions sont indiquées.

General Information

Status
Published
Publication Date
12-Nov-2019
Current Stage
PPUB - Publication issued
Completion Date
13-Nov-2019
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IEC 60747-5-8
Edition 1.0 2019-11
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Semiconductor devices –
Part 5-8: Optoelectronic devices – Light emitting diodes – Test method of
optoelectronic efficiencies of light emitting diodes
Dispositifs à semiconducteurs –
Partie 5-8: Dispositifs optoélectroniques – Diodes électroluminescentes –
Méthode d’essai des efficacités optoélectroniques des diodes
électroluminescentes
IEC 60747-5-8:2019-11(en-fr)
---------------------- Page: 1 ----------------------
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---------------------- Page: 2 ----------------------
IEC 60747-5-8
Edition 1.0 2019-11
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Semiconductor devices –
Part 5-8: Optoelectronic devices – Light emitting diodes – Test method of
optoelectronic efficiencies of light emitting diodes
Dispositifs à semiconducteurs –
Partie 5-8: Dispositifs optoélectroniques – Diodes électroluminescentes –
Méthode d’essai des efficacités optoélectroniques des diodes
électroluminescentes
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 31.080.99 ISBN 978-2-8322-7589-4

Warning! Make sure that you obtained this publication from an authorized distributor.

Attention! Veuillez vous assurer que vous avez obtenu cette publication via un distributeur agréé.

® Registered trademark of the International Electrotechnical Commission
Marque déposée de la Commission Electrotechnique Internationale
---------------------- Page: 3 ----------------------
– 2 – IEC 60747-5-8:2019 © IEC 2019
CONTENTS

FOREWORD ........................................................................................................................... 3

1 Scope .............................................................................................................................. 5

2 Normative references ...................................................................................................... 5

3 Terms and definitions ...................................................................................................... 5

3.1 General terms and definitions ................................................................................. 5

3.2 Terms and definitions relating to the measurement of the efficiency ........................ 6

4 Measuring methods ......................................................................................................... 8

4.1 Basic requirements ................................................................................................. 8

4.1.1 Measuring conditions ....................................................................................... 8

4.1.2 Measuring instruments and equipment ............................................................. 8

4.2 Power efficiency (η ) measurement ....................................................................... 8

4.2.1 Purpose ........................................................................................................... 8

4.2.2 Measurement procedure .................................................................................. 8

4.3 External quantum efficiency (η ) measurement ................................................... 9

EQE

4.3.1 Purpose ........................................................................................................... 9

4.3.2 Measurement procedure .................................................................................. 9

4.4 Voltage efficiency (η ) measurement ..................................................................... 9

4.4.1 Purpose ........................................................................................................... 9

4.4.2 Measurement procedure .................................................................................. 9

4.5 Internal quantum efficiency (η ) measurement ................................................... 10

IQE

4.6 Light extraction efficiency (η ) measurement ..................................................... 10

LEE

4.6.1 Purpose ......................................................................................................... 10

4.6.2 Measurement procedure ................................................................................ 10

4.7 Measurement sequences ...................................................................................... 10

5 Test report ..................................................................................................................... 11

Annex A (informative) Test example..................................................................................... 12

Bibliography .......................................................................................................................... 18

Figure 1 – Sequences of the efficiency measurements .......................................................... 11

Figure A.1 – Radiant power and forward voltage as a function of forward current ................. 12

Figure A.2 – Power efficiency as a function of forward current .............................................. 13

Figure A.3 – Emission spectrum distribution versus wavelength ............................................ 13

Figure A.4 – Mean photon energy as a function of forward current ........................................ 14

Figure A.5 – External quantum efficiency as a function of forward current ............................. 14

Figure A.6 – Voltage efficiency as a function of forward current ............................................ 15

Figure A.7 – Internal quantum efficiency as a function of forward current .............................. 15

Figure A.8 – Light extraction efficiency as a function of forward current ................................ 16

Figure A.9 – Optoelectronic efficiencies as a function of forward current: PE, EQE, VE,

IQE, and LEE ........................................................................................................................ 16

Table A.1 – Summary of test report ....................................................................................... 17

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IEC 60747-5-8:2019 © IEC 2019 – 3 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
SEMICONDUCTOR DEVICES –
Part 5-8: Optoelectronic devices – Light emitting diodes –
Test method of optoelectronic efficiencies of light emitting diodes
FOREWORD

1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising

all national electrotechnical committees (IEC National Committees). The object of IEC is to promote

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8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is

indispensable for the correct application of this publication.

9) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of

patent rights. IEC shall not be held responsible for identifying any or all such patent rights.

International Standard IEC 60747-5-8 has been prepared by subcommittee 47E: Discrete

semiconductor devices, of IEC technical committee 47: Semiconductor devices.
The text of this International Standard is based on the following documents:
CDV Report on voting
47E/637/CDV 47E/658/RVC

Full information on the voting for the approval of this International Standard can be found in

the report on voting indicated in the above table.

This document has been drafted in accordance with the ISO/IEC Directives, Part 2.

A list of all parts in the IEC 60747 series, published under the general title Semiconductor

devices, can be found on the IEC website.
---------------------- Page: 5 ----------------------
– 4 – IEC 60747-5-8:2019 © IEC 2019

Future standards in this series will carry the new general title as cited above. Titles of existing

standards in this series will be updated at the time of the next edition.

The committee has decided that the contents of this document will remain unchanged until the

stability date indicated on the IEC website under "http://webstore.iec.ch" in the data related to

the specific document. At this date, the document will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.

IMPORTANT – The 'colour inside' logo on the cover page of this publication indicates

that it contains colours which are considered to be useful for the correct

understanding of its contents. Users should therefore print this document using a

colour printer.
---------------------- Page: 6 ----------------------
IEC 60747-5-8:2019 © IEC 2019 – 5 –
SEMICONDUCTOR DEVICES –
Part 5-8: Optoelectronic devices – Light emitting diodes –
Test method of optoelectronic efficiencies of light emitting diodes
1 Scope

This part of IEC 60747 specifies the terminology and the measuring methods of various

efficiencies of single light emitting diode (LED) chips or packages without phosphor. White

LEDs for lighting applications are out of the scope of this part of IEC 60747. The efficiencies

whose measuring methods are defined in this part are the power efficiency (PE), the external

quantum efficiency (EQE), the voltage efficiency (VE), and the light extraction efficiency (LEE).

To measure the LEE, the measurement data of the internal quantum efficiency (IQE) is used,

1 2

whose measuring method is discussed in IEC 60747-5-9 and IEC 60747-5-10 . The injection

efficiency (IE) and the radiative efficiency (RE) are given definitions only.
2 Normative references

The following documents are referred to in the text in such a way that some or all of their

content shall constitute 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.

IEC 60747-5-6:2016, Semiconductor devices – Part 5-6: Optoelectronic devices – Light

emitting diodes
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.

ISO and IEC maintain terminological databases for use in standardization at the following

addresses:
• IEC Electropedia: available at http://www.electropedia.org/
• ISO Online browsing platform: available at http://www.iso.org/obp
3.1 General terms and definitions
3.1.1
radiant power
power emitted, transmitted or received in the form of radiation

Note 1 to entry: The unit used is: W. Radiant power is also known as the “radiant flux”.

[SOURCE: IEC 60050-845:1987, 845-01-24, modified – The symbol has been added to the

term and Note 1 has been expanded.]
___________
Under preparation. Stage at the time of publication IEC RPUB 60747-5-9:2019.
Under preparation. Stage at the time of publication IEC RPUB 60747-5-10:2019.
---------------------- Page: 7 ----------------------
– 6 – IEC 60747-5-8:2019 © IEC 2019
3.1.2
spectral distribution

quotient of the radiant power contained in an elementary range dλ of wavelength at

the wavelength λ , by that range
dΦλ
( )
Φ =
e,λ
Note 1 to entry: Spectral distribution is also known as “spectrum distribution”.

[SOURCE: IEC 60050-845:1987, 845-01-17, modified – In the definition, "or luminous or

photon quantity dX(λ)" has been replaced by "power dΦ ", in the formula, X has been

replaced by Φ ; Note 1 has been updated and Note 2 deleted.]
3.1.3
mean photon energy
mean energy that each photon carries
hν=
Φλd
e,λ
where
h is the Planck constant;
c is the speed of light in vacuum
3.2 Terms and definitions relating to the measurement of the efficiency
3.2.1
power efficiency

ratio of the radiant power (coupled to free space), Φ , to the electrical power consumed by

the LED, V I , where V is the forward voltage and I is the forward current of the LED

F F F F
η =
F F

Note 1 to entry Power efficiency is also known as “wall-plug efficiency”. Power efficiency is identical to the

“radiant efficiency” when the power dissipated by any auxiliary equipment is excluded from the electrical power.

3.2.2
voltage efficiency

ratio of the mean photon energy emitted from the LED to the electron energy given by the

forward voltage of the LED, V
η =
where
q is the elementary charge

Note 1 to entry: Voltage efficiency can be greater than 1 at very low forward currents.

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IEC 60747-5-8:2019 © IEC 2019 – 7 –
3.2.3
external quantum efficiency
EQE

ratio of the number of photons emitted into the free space per unit time to the number of

electrons injected into the LED per unit time
Φhν
η =
EQE
3.2.4
internal quantum efficiency
IQE

ratio of the number of photons emitted from the active region per unit time to the number of

electrons injected into the LED per unit time
Φhν
e,active
η =
IQE
where
Φ is the radiant power emitted from the active region
e,active
3.2.5
light extraction efficiency
LEE

ratio of the number of photons emitted into the free space to the number of photons emitted

from the active region
η =
LEE
e,active
3.2.6
injection efficiency

ratio of the number of electrons injected into the active region per unit time to the number of

electrons injected into the LED per unit time
F,active
η =
where
Ι is the portion of the forward current injected into the active region
F,active
3.2.7
radiative efficiency

ratio of the number of photons emitted from the active region per

unit time to the number of electrons injected into the active region per unit time

Φνh
e,active
η =
F,active
---------------------- Page: 9 ----------------------
– 8 – IEC 60747-5-8:2019 © IEC 2019

Note 1 to entry The power efficiency can be decomposed into various constituent efficiencies as follows:

η ηη⋅
PE VE EQE
=ηη⋅⋅η
VE LEE IQE
=η⋅η⋅⋅ηη
VE LEE IE RE
η ηη⋅
EQE LEE IQE
η ηη⋅
IQE IE RE
Using the efficiency definitions, the above can rewritten as:
η =
F F
IhΦν
hν Φ
F,active e,active
=⋅ ⋅⋅
qV Φ I I q
F e,active F F,active
4 Measuring methods
4.1 Basic requirements
4.1.1 Measuring conditions
a) Temperature
If not specified, measurements shall be made at an ambient temperature (T ) of
(25 ± 3) °C in conditions of free air.
b) Humidity

When humidity conditions are not specified, relative humidity shall be between 45 % RH

and 85 % RH.
c) Other conditions

In some cases, measurements change because of heat generation in the test LED over

time. In that case, it is necessary to decide on the measurement time, otherwise the

measurement shall be performed after reaching thermal equilibrium. Thermal equilibrium

may be considered to have been achieved if doubling the time between the application of

power and the measurement causes no change in the indicated result within the precision

of the measurement instruments.
4.1.2 Measuring instruments and equipment
Measuring instruments and equipment shall be the same as given in 6.1.2 of
IEC 60747-5-6:2016.
4.2 Power efficiency (η ) measurement
4.2.1 Purpose

To measure the power efficiency of the LED when a specified forward current is applied.

4.2.2 Measurement procedure
The measurement procedure is as follows:

a) Measure the radiant power (Φ ) and the forward voltage (V ) at a specified forward current

e F
(I ).
---------------------- Page: 10 ----------------------
IEC 60747-5-8:2019 © IEC 2019 – 9 –

b) Calculate the power efficiency by taking the ratio of the radiant power (coupled to the free

space), Φ , to the input electrical power V I , i.e.:
e F F
η =
F F

NOTE 1 The measurement of the forward voltage at a specified forward current is given in 6.2 of

IEC 60747-5-6:2016.

NOTE 2 The measurement of the radiant power at a specified current is given in 6.11 of IEC 60747-5-6:2016.

4.3 External quantum efficiency (η ) measurement
EQE
4.3.1 Purpose

To measure the external quantum efficiency of the LED when a specified forward current is

applied.
4.3.2 Measurement procedure
The measurement procedure is as follows.
a) Measure the radiant power (Φ ) at a specified forward current (I ).
e F
b) Measure the emission spectrum distribution (Φ ).
e,λ
c) Calculate the mean photon energy (hν ) by using the following formula:
hν=
Φλd
e,λ

d) Calculate the external quantum efficiency by taking the ratio of the number of photons

emitted into free space per unit time to the number of electrons injected into the LED per

unit time, i.e.:
Φhν
η =
EQE

NOTE 1 The measurement of the radiant power at a specified current is listed in 6.11 of IEC 60747-5-6:2016.

NOTE 2 The measurement method of the emission spectrum distribution is listed in 6.15 of IEC 60747-5-6:2016.

4.4 Voltage efficiency (η ) measurement
4.4.1 Purpose

To measure the voltage efficiency of the LED when a specified forward current is applied.

4.4.2 Measurement procedure
The measurement procedure is as follows.

Calculate the voltage efficiency by taking the ratio of the power efficiency to the external

quantum efficiency, i.e.:
η =
EQE
---------------------- Page: 11 ----------------------
– 10 – IEC 60747-5-8:2019 © IEC 2019
NOTE 1 For the measurement of the power efficiency, see 4.2.
NOTE 2 For the measurement of the external quantum efficiency, see 4.3.
4.5 Internal quantum efficiency (η ) measurement
IQE

The measurement methods of the internal quantum efficiency are defined in other documents

currently being developed.
4.6 Light extraction efficiency (η ) measurement
LEE
4.6.1 Purpose

To measure the light extraction efficiency of the LED when a specified forward current is

applied.
4.6.2 Measurement procedure
The measurement procedure is as follows.

Calculate the light extraction efficiency by taking the ratio of the external quantum efficiency

to the internal quantum efficiency, i.e.:
EQE
η =
LEE
IQE
NOTE 1 For the measurement of the external quantum efficiency, see 4.3.
NOTE 2 For the measurement of the internal quantum efficiency, see 4.5.
4.7 Measurement sequences

Figure 1 summarizes the measurement sequences of each efficiency of the LED when a

specified forward current is applied. A test example is given in Annex A.
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IEC 60747-5-8:2019 © IEC 2019 – 11 –
Figure 1 – Sequences of the efficiency measurements
5 Test report
The test report should include the items shown in Table A.1.
---------------------- Page: 13 ----------------------
– 12 – IEC 60747-5-8:2019 © IEC 2019
Annex A
(informative)
Test example
• Step 0: Test environmental specifications
– sample: a lateral-electrode type InGaN/GaN MQW LED grown on a c-plane sapphire
substrate;
– chip size: 740 μm × 600 μm;
– peak wavelength: ~450 nm at T = 293 K;
– humidity: 50 % RH;

– current driving condition: pulsed current driving condition (pulse width: 1 ms, duty cycle:

1 %);
– detector for radiant power measurement: Si photodiode;
– equipment for electrical characteristics measurement: Keithley semiconductor
parameter analyser;
– maximum driving current, I = 350 mA;
max
– total number of data points, N = 65.

• Step 1: Acquire N data consisting of radiant power and forward voltage as a function of

forward current, as shown in Figure A.1.
Figure A.1 – Radiant power and forward voltage
as a function of forward current
___________

This information is given for the convenience of users of this document and does not constitute an endorsement

by IEC of the product named. Equivalent products may be used if they can be shown to lead to the same results.

---------------------- Page: 14 ----------------------
IEC 60747-5-8:2019 © IEC 2019 – 13 –

• Step 2: Calculate the power efficiency by taking the ratio of the radiant power to the input

electrical power (see Figure A.2).
Figure A.2 – Power efficiency as a function of forward current

• Step 3: Measure the emission spectrum distribution (see Figure A.3) and calculate the

mean photon energy (see Figure A.4) by using
hν=
Φλd
e,λ
Figure A.3 – Emission spectrum distribution versus wavelength
---------------------- Page: 15 ----------------------
– 14 – IEC 60747-5-8:2019 © IEC 2019
Figure A.4 – Mean photon energy as a function of forward current

• Step 4: Calculate the external quantum efficiency by taking the ratio of the number of

photons emitted into the free space per unit time to the number of electrons injected into

the LED per unit time (see Figure A.5), i.e.:
Φhν
η =
EQE
Figure A.5 – External quantum efficiency as a function of forward current
---------------------- Page: 16 ----------------------
IEC 60747-5-8:2019 © IEC 2019 – 15 –

• Step 5: Calculate the voltage efficiency by taking the ratio of the power efficiency to the

external quantum efficiency (see Figure A.6).
Figure A.6 – Voltage efficiency as a function of forward current

• Step 6: Measure the internal quantum efficiency (see Figure A.7) using one of the

methods defined in IEC 60747-5-9 and IEC 60747-5-10.
Figure A.7 – Internal quantum efficiency as a function of forward current
---------------------- Page: 17 ----------------------
– 16 – IEC 60747-5-8:2019 © IEC 2019

• Step 7: Calculate the light extraction efficiency by taking the ratio of the external quantum

efficiency to the internal quantum efficiency (see Figure A.8).
Figure A.8 – Light extraction efficiency as a function of forward current

• Step 8: Create the test report. The measured optoelectronic efficiencies are summarized

in Figure A.9.
Figure A.9 – Optoelectronic efficiencies as a function of forward current:
PE, EQE, VE, IQE, and LEE
---------------------- Page: 18 ----------------------
IEC 60747-5-8:2019 © IEC 2019 – 17 –
Table A.1 – Summary of test report
Item Unit Value Comment
LED maker - Specify the name of the company
Model name - Specify the model name
Chip size
[µm] × [µm]
Package type - Ex. SMD
Peak wavelength [nm]
Maximum applied current (I ) [mA]
max
Data points N -
Pulse width [ms]
Duty cycle [%]
Detector t
...

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