This article introduces the basic principles and calculation formulas of electroluminescence EQE measurement, explains the correspondence between the measured quantities and calculated quantities obtained during actual measurement with the Pynect EQE external quantum efficiency test system, and helps readers understand the calculation logic of each step to improve their ability to evaluate data and analyze problems.

1 Performance Metrics of Perovskite Light-Emitting Diodes

1.1 What Is a Perovskite Light-Emitting Diode

A perovskite light-emitting diode (Perovskite Light-Emitting Diode, PeLED for short) is a class of electroluminescent devices that use metal-halide perovskite as the emissive layer. Metal-halide perovskites feature a readily tunable bandgap, narrow emission spectrum (full width at half maximum about 20 nm), high color purity, high photoluminescence quantum yield (Photoluminescence Quantum Yield, PLQY), high carrier mobility and low-temperature solution processability, and are regarded as a strong candidate for next-generation display and lighting technology. Since the first room-temperature-working PeLED emerged in 2014, the external quantum efficiency (External Quantum Efficiency, EQE) of green, red and near-infrared PeLEDs has successively surpassed 20%, approaching the level of organic light-emitting diodes (OLEDs).

In terms of device type, perovskite light-emitting diodes (PeLEDs) belong to the same family of electroluminescence (Electroluminescence, EL) devices as organic light-emitting diodes (OLEDs) and quantum-dot light-emitting diodes (Quantum-dot Light-Emitting Diode, QLEDs): the anode injects holes and the cathode injects electrons, and the two recombine in the emissive layer to release energy in the form of photons. The only core difference among the three lies in the emissive-layer material, so the core metric used to evaluate them — external quantum efficiency (EQE) — is completely universal in definition and algorithm.

1.2 Terminology of the Light-Emitting Diode (LED) Family

Abbreviation Full name Chinese Emissive-layer material
LED Light-Emitting Diode 发光二极管 Inorganic III-V group (GaN, GaAs, etc.)
OLED Organic Light-Emitting Diode 有机发光二极管 Organic small molecules / polymers
PLED Polymer Light-Emitting Diode 聚合物发光二极管 Conjugated polymers (an OLED subclass)
QLED Quantum-dot Light-Emitting Diode 量子点发光二极管 Inorganic semiconductor quantum dots
PeLED Perovskite Light-Emitting Diode 钙钛矿发光二极管 Metal-halide perovskite

1.3 External Quantum Efficiency (EQE) — the Core Yardstick of Device Performance

External quantum efficiency (External Quantum Efficiency, EQE) is the most important and most comprehensive performance metric for evaluating light-emitting diodes. It is defined as the ratio of the number of photons emitted by the device into free space per unit time to the number of electrons injected into the device.

$$EQE = \frac{N_{photons}}{N_{electrons}} \times 100\%$$(Formula 1)

EQE reflects the combined efficiency of the entire chain from charge injection to light out-coupling, and can be decomposed step by step into the product of four physical processes:

$$EQE = \eta_{inj} \cdot \eta_r \cdot PLQY \cdot \eta_{out}$$(Formula 2)

  • Carrier injection efficiency $\eta_{inj}$: the degree of balance between the numbers of injected electrons and holes (charge balance factor);
  • Radiative recombination efficiency $\eta_r$: the proportion of injected carriers that undergo radiative recombination and produce photons;
  • Photoluminescence quantum yield $PLQY$: the proportion of absorbed excitation energy re-released in the form of photons by the emissive layer; a material-level metric obtained from photoluminescence (Photoluminescence, PL) measurement;
  • Light out-coupling efficiency $\eta_{out}$: the proportion of photons generated inside the emissive layer that ultimately escape the device and enter free space, constrained by losses such as substrate modes, waveguide modes and surface plasmon modes.

Two pairs of concepts must be distinguished in particular:

  • Photoluminescence (PL) vs. electroluminescence (EL): PL excites the material with light to emit, corresponding to the material-level metric PLQY; EL emits through current injection, corresponding to the device-level metric EQE.
  • Photoluminescence quantum yield (PLQY) vs. external quantum efficiency (EQE): PLQY measures only the light-conversion efficiency of the emissive layer itself; EQE adds injection efficiency, radiative recombination efficiency and light out-coupling efficiency on top of PLQY, representing the combined efficiency of the complete device.

1.4 Other Key Performance Metrics of PeLEDs

Besides EQE, the following metrics are also commonly considered in PeLED evaluation:

Metric Meaning
Radiant flux Total optical power within a specified wavelength band
Luminance Luminous intensity per unit area in the visible band, in cd·m⁻²
CIE color coordinates Characterize the emission color and color purity
Peak wavelength and full width at half maximum (FWHM) The spectral peak wavelength and its width at half maximum
Current efficiency (CE) Ratio of luminance to current density, in cd·A⁻¹
Power efficiency (PE) Ratio of luminous flux to electrical power, in lm·W⁻¹
Lifetime Time required for the luminance or radiant flux to decay to a certain proportion under constant voltage/current (e.g., T50, T70)

2 Basic Physical Quantities

2.1 Overview of Radiometry and Photometry

The optical measurement of light-emitting LEDs involves three sets of physical quantities: radiometry, photometry and colorimetry. These concepts are interrelated and their symbols are numerous; many test and research personnel do not fully understand their physical meanings and often stop at a superficial level because of their complexity. In fact, a proper understanding of the physical meaning and mathematical expression of the measured quantities helps one evaluate measurement results more accurately and analyze experimental problems, and is also of practical reference value for carrying out experiments. Based on textbooks and national standards, and in combination with actual LED measurement scenarios, this chapter systematically reviews the relevant optical quantities and their calculation relationships.

2.2 Measurement Context and Overview of Quantities

In an LED EQE measurement system, the integrating sphere collects all the emitted light of the sample under test and funnels the luminous flux to the spectrometer regardless of direction. Therefore the measurement chain only produces "total amount" and "spectral distribution" information, and does not involve spatial distribution quantities along a specific direction or per unit solid angle. Accordingly, this chapter discusses only the quantities that actually appear in the measurement, using luminous flux as the photometric bridge:

Quantity Symbol Unit Defining formula
Radiant flux (radiant power) $\Phi_e$ W $\Phi_e = dQ_e/dt$
Spectral radiant flux (spectral concentration of radiant flux) $\Phi_{e,\lambda}$ W·nm⁻¹ $\Phi_{e,\lambda} = d\Phi_e/d\lambda$
Luminous flux $\Phi_v$ lm $\Phi_v = K_m \int \Phi_{e,\lambda} \cdot V(\lambda)\,d\lambda$
Radiance $L_e$ W·m⁻²·sr⁻¹ $L_e = d^2\Phi_e/(d\Omega \cdot dA \cdot \cos\theta)$
Luminance $L_v$ cd·m⁻² $L_v = d^2\Phi_v/(d\Omega \cdot dA \cdot \cos\theta)$

Luminous intensity (cd) and radiant intensity (W·sr⁻¹) are quantities of a point source along a certain direction per unit solid angle, while irradiance (W·m⁻²) is the quantity "received per unit area of an illuminated surface" — all three require direction or incidence-area information, which cannot and need not be given under integrating-sphere total-collection measurement, so they are outside the scope of this chapter.

2.3 Radiometric Quantities

2.3.1 Radiant Flux

Power emitted, propagated or received in the form of radiation, i.e., the radiant energy passing through a certain region per unit time:

$$\Phi_e = \frac{dQ_e}{dt}$$(Formula 3)

Unit: W (watt). The "total optical power" measured by the integrating sphere is the sum of the radiant flux of the LED over the entire emission space, and is the source of all subsequent quantities.

2.3.2 Spectral Radiant Flux

The spectral concentration of radiant flux, i.e., the radiant flux within a unit wavelength interval at wavelength $\lambda$:

$$\Phi_{e,\lambda} = \frac{d\Phi_e}{d\lambda}$$(Formula 4)

The standard unit is W·m⁻¹; in engineering, wavelength is recorded in nm, and W·nm⁻¹ (or μW·nm⁻¹) is commonly used. The formal name is "spectral concentration of radiant flux", abbreviated as "spectral radiant flux"; saying "spectral concentration" alone without specifying the quantity it belongs to, or using non-standard terms such as "optical power density", is not rigorous. The radiant flux within a range $\Delta\lambda$ at a certain wavelength $\lambda$ is:

$$\Phi_e(\lambda) \approx \Phi_{e,\lambda} \cdot \Delta\lambda$$(Formula 5)

2.3.3 Radiance

The radiant flux per unit apparent area (projected area) per unit solid angle in a specified direction:

$$L_e = \frac{d^2\Phi_e}{d\Omega \cdot dA \cdot \cos\theta}$$(Formula 6)

Unit: W·m⁻²·sr⁻¹. Here $dA$ is the emitting surface element, $\theta$ is the angle between the observation direction and the surface-element normal, $dA \cdot \cos\theta$ is the apparent area (projected area) in that direction, and $d\Omega$ is the solid-angle element. In integrating-sphere measurement, radiance is not measured direction by direction but is an equivalent quantity converted from the total flux and the emitting area under the Lambertian assumption.

2.4 Photometric Quantities

2.4.1 Luminous Flux and Spectral Luminous Efficiency

Luminous flux is the weighted measure of radiant flux by the human visual system:

$$\Phi_v = K_m \int \Phi_{e,\lambda} \cdot V(\lambda)\, d\lambda$$(Formula 7)

where $V(\lambda)$ is the photopic spectral luminous efficiency function (dimensionless, 0-1), describing the relative sensitivity of the human eye to different wavelengths, with its peak at $\lambda = 555$ nm; $K_m = 683$ lm·W⁻¹ is the maximum spectral luminous efficacy. Unit: lm (lumen). Luminous flux is the only bridge connecting radiometric and photometric quantities, and is also the basis for luminance calculation.

2.4.2 Luminance

The luminous flux per unit apparent area (projected area) per unit solid angle in a specified direction:

$$L_v = \frac{d^2\Phi_v}{d\Omega \cdot dA \cdot \cos\theta}$$(Formula 8)

Unit: cd·m⁻² (candela per square meter), also called nit, $1\ \mathrm{cd \cdot m^{-2}} = 1\ \mathrm{lm \cdot m^{-2} \cdot sr^{-1}}$. Luminance describes "how bright a surface source looks", directly corresponding to the subjective brightness perceived by the human eye and cameras, and is an important specification metric of LEDs.

2.5 Relationships Among the Quantities

2.5.1 Correspondence Between Radiometric and Photometric Quantities

The two correspond point by point; the only difference is that photometric quantities introduce weighting by the spectral luminous efficiency $V(\lambda)$:

Radiometric quantity Photometric quantity Conversion relationship
Radiant flux $\Phi_e$ (W) Luminous flux $\Phi_v$ (lm) $\Phi_v = K_m \int \Phi_{e,\lambda} \cdot V(\lambda)\,d\lambda$
Radiance $L_e$ (W·m⁻²·sr⁻¹) Luminance $L_v$ (cd·m⁻²) $L_v = K_m \int L_{e,\lambda} \cdot V(\lambda)\,d\lambda$

2.5.2 Relationship Between Total Flux and Radiance / Luminance

For a Lambertian body (uniform luminance, constant in all directions), integrate the defining formulas over the hemispherical space of single-sided emission (solid angle $2\pi$ sr):

$$\Phi_e = L_e \cdot A \int_0^{2\pi} d\varphi \int_0^{\pi/2} \cos\theta \sin\theta\, d\theta = \pi \cdot A \cdot L_e$$(Formula 9)

$$\Phi_v = L_v \cdot A \int_0^{2\pi} d\varphi \int_0^{\pi/2} \cos\theta \sin\theta\, d\theta = \pi \cdot A \cdot L_v$$(Formula 10)

Solving inversely gives the equivalent radiance and luminance in integrating-sphere measurement:

$$L_e = \frac{\Phi_e}{\pi \cdot A}, \quad L_v = \frac{\Phi_v}{\pi \cdot A}$$(Formula 11)

where $\pi$ is the coefficient after cosine-weighted integration: $\cos\theta$ is the projection factor in the defining formulas (apparent area $dA \cdot \cos\theta$), and after integration $\int \cos\theta\, d\Omega = \pi$; although the hemispherical solid angle is $2\pi$ sr, the coefficient is $\pi$, not $2\pi$. Furthermore, since sr = m²/m² is dimensionless, the sr⁻¹ in $L$ is only a semantic marker, so $\Phi = \pi \cdot A \cdot L$ is dimensionally self-consistent.

2.5.3 Relationship Between Spectral Quantities and Total Quantities

Radiant flux is the integral of spectral radiant flux over wavelength (a summation in the discrete case):

$$\Phi_e = \int \Phi_{e,\lambda}\, d\lambda \approx \sum \Phi_{e,\lambda} \cdot \Delta\lambda$$(Formula 12)

Thus the measurement chain is completely closed: the spectrometer measures $\Phi_{e,\lambda}$ → summation yields $\Phi_e$ → weighting by $V(\lambda)$ yields the luminous flux $\Phi_v$ → division by $\pi \cdot A$ yields the radiance $L_e$ and luminance $L_v$.

3 Inputs and Outputs

In the measurement system, there are only two categories of directly measured physical quantities: the spectral radiant flux $\Phi_{e,\lambda}$ acquired by the spectrometer and obtained through radiometric calibration, and the voltage $U$ and current $I$ read by the source meter. All other quantities displayed by the test software (intermediate and result quantities) are calculated from these two categories of input using the formulas in Chapter 4. Understanding the correspondence from INPUT (measured quantities and lookup-table functions) to OUTPUT (intermediate and result quantities) helps experimenters understand experimental phenomena and analyze data.

In Table 1, OUTPUT is the intermediate or result quantity displayed by the test software; the symbols and units of all quantities uniformly adopt the notation defined in Chapter 2 and summarized in Section 4.1 of Chapter 4.

Table 1 Input-Output Concept Table

OUTPUT INPUT Data source
Spectral radiant flux $\Phi_{e,\lambda}$ Relative intensity spectrum, lamp file Spectrometer, radiometric calibration source
J-V curve Source-meter voltage and current values Source meter
Current density Emitting area $A$, current $I$ Device, source meter
Luminance, radiance Spectral radiant flux $\Phi_{e,\lambda}$, luminous efficiency function (lookup table) —
Peak wavelength, full width at half maximum (FWHM) Spectral radiant flux $\Phi_{e,\lambda}$ —
L-J curve Luminance, current density —
x,y chromaticity coordinates Spectral radiant flux $\Phi_{e,\lambda}$, tristimulus values (lookup table) —
EQE Spectral radiant flux $\Phi_{e,\lambda}$, current density —
CE (current efficiency) Luminance, current density —

4 Calculation Principles

Chapter 2 has already given the definitions of the quantities and their interrelationships; this chapter does not repeat the definitions but only gives the concrete calculation steps for obtaining each result quantity from the measurement data. To ensure consistency, the symbols and units participating in the calculation are first agreed upon, and then the calculation formulas for radiant flux, luminance, radiance, external quantum efficiency, chromaticity coordinates and efficiency parameters are given one by one.

4.1 Symbol and Unit Conventions

The raw data output by the spectrometer after radiometric calibration is the spectral radiant flux (i.e., the spectral concentration of radiant flux) $\Phi_{e,\lambda}$, in μW/nm; the source meter provides voltage $U$ (mV) and current $I$ (mA); the area of the device under test is denoted $A$ (mm²); and the wavelength sampling interval is denoted $\Delta\lambda$ (nm). The physical quantities participating in the calculation and their units are summarized in the table below:

Symbol Quantity Unit
$A$ Emitting area mm²
$I$ Current mA
$U$ Voltage mV
$J$ Current density mA/cm²
$\lambda$ Wavelength nm
$\Delta\lambda$ Wavelength sampling interval nm
$\Phi_{e,\lambda}$ Spectral radiant flux (spectral concentration of radiant flux) μW/nm
$\Phi_e(\lambda)$ Radiant flux within $\Delta\lambda$ at wavelength $\lambda$ μW
$\Phi_e$ Total radiant flux μW
$\Phi_v$ Total luminous flux lm
$L_v$ Luminance cd/m²
$L_e$ Radiance W/(sr·m²)

If a coordinate axis needs to be displayed in other units, it will be stated separately, but all quantities substituted into the formulas follow the units in the table above.

4.2 Radiant Flux Calculation

The radiant flux (μW) within a width $\Delta\lambda$ at the center wavelength $\lambda$ equals the spectral radiant flux multiplied by the sampling interval:

$$\Phi_e(\lambda) = \Phi_{e,\lambda} \times \Delta\lambda$$(Formula 13)

The total radiant flux is the sum of the radiant flux of each wavelength interval within the measurement band $[a, b]$, where $a$ and $b$ are the lower and upper limits of the measurement wavelength range (in nm) and are not restricted by the luminous efficiency function:

$$\Phi_e = \sum_{\lambda=a}^{b} \Phi_e(\lambda) = \sum_{\lambda=a}^{b} \Phi_{e,\lambda} \cdot \Delta\lambda$$(Formula 14)

Radiant flux is the input quantity for all subsequent results such as luminance, radiance and EQE, and its value comes directly from the spectral data after the spectrometer's radiometric calibration.

4.3 Luminance Calculation

Photometric and radiometric quantities correspond one to one, the only difference being whether they are weighted by the luminous efficiency function $V(\lambda)$. The luminous flux (lm) at wavelength $\lambda$ is:

$$\Phi_v(\lambda) = 683 \times V(\lambda) \times \Phi_e(\lambda)$$(Formula 15)

where $V(\lambda)$ is the CIE photopic spectral luminous efficiency function (dimensionless), and 683 lm/W is the maximum spectral luminous efficacy $K_m$.

The device is approximated as a Lambertian body (uniform luminance, constant in all directions); integrating over the hemispherical space gives the relationship between luminous flux and luminance:

$$\Phi_v(\lambda) = \pi \cdot A \cdot L_v(\lambda)$$(Formula 16)

Therefore the single-wavelength luminance at wavelength $\lambda$ is:

$$L_v(\lambda) = \frac{\Phi_v(\lambda)}{\pi \cdot A}$$(Formula 17)

The total luminance is the sum of the single-wavelength luminance values over the visible range:

$$L_v = \frac{1}{\pi \cdot A} \sum_{\lambda=380}^{780} \Phi_v(\lambda)$$(Formula 18)

The unit of luminance is cd/m² (nit, nt).

4.4 Radiance Calculation

Radiance has exactly the same form as luminance; the only difference is that it is not weighted by the luminous efficiency function. The single-wavelength radiance and total radiance are respectively:

$$L_e(\lambda) = \frac{\Phi_e(\lambda)}{\pi \cdot A}$$(Formula 19)

$$L_e = \frac{1}{\pi \cdot A} \sum_{\lambda=a}^{b} \Phi_e(\lambda)$$(Formula 20)

The unit of radiance is W/(sr·m²).

4.5 External Quantum Efficiency EQE

EQE is the ratio of the number of photons emitted by the device to the number of injected electrons. The energy of a single photon at wavelength $\lambda$ is:

$$E_{ph}(\lambda) = \frac{h \cdot c}{\lambda}$$(Formula 21)

Therefore the number of photons emitted per second at wavelength $\lambda$ is:

$$N(\lambda) = \frac{\Phi_e(\lambda)}{E_{ph}(\lambda)} = \frac{\Phi_e(\lambda) \cdot \lambda}{h \cdot c}$$(Formula 22)

The total number of photons within the measurement band $[a, b]$ and the number of electrons injected per second are respectively:

$$N_t = \sum_{\lambda=a}^{b} N(\lambda)$$(Formula 23)

$$N_e = \frac{I}{q}$$(Formula 24)

Combining Formulas 22, 23 and 24 yields the external quantum efficiency:

$$EQE = \frac{N_t}{N_e} = \frac{q}{h \cdot c \cdot I} \sum_{\lambda=a}^{b} \Phi_e(\lambda) \cdot \lambda$$(Formula 25)

where the Planck constant $h = 6.62607015 \times 10^{-34}$ J·s, the speed of light $c = 2.99792458 \times 10^8$ m/s, and the elementary charge $q = 1.602176634 \times 10^{-19}$ C. When substituting into the formula above, the current $I$ must be in A, the radiant flux $\Phi_e(\lambda)$ in W and the wavelength $\lambda$ in m; otherwise an order-of-magnitude error will be introduced. In actual calculation, these are converted from mA, μW and nm.

4.6 CIE 1931 Chromaticity Coordinates

The tristimulus values of a self-luminous device are obtained by the weighted summation of radiant flux and the CIE 1931 color matching functions, directly taking the normalization coefficient $k=1$:

$$X = \sum_{\lambda=380}^{780} \Phi_e(\lambda)\, \bar{x}(\lambda)$$(Formula 26)

$$Y = \sum_{\lambda=380}^{780} \Phi_e(\lambda)\, \bar{y}(\lambda)$$(Formula 27)

$$Z = \sum_{\lambda=380}^{780} \Phi_e(\lambda)\, \bar{z}(\lambda)$$(Formula 28)

where $\bar{x}(\lambda)$, $\bar{y}(\lambda)$ and $\bar{z}(\lambda)$ are the color matching functions of the CIE 1931 standard colorimetric observer (obtained by table lookup). The chromaticity coordinates are:

$$x = \frac{X}{X+Y+Z}, \quad y = \frac{Y}{X+Y+Z}$$(Formula 29)

For a self-luminous LED, any positive value of $k$ cancels out in the ratio of the chromaticity coordinates and does not affect the $x$, $y$ results, so 1 is taken directly here. Note: CIE 1931 is a 2° observer system; a 10° observer requires switching to the CIE 1964 system.

4.7 Power Conversion Efficiency, Current Efficiency and Power Efficiency

The power conversion efficiency PCE is the ratio of the total radiant flux to the electrical power; it is dimensionless (often expressed as a percentage). Here the electrical power $P = I \times U$, and when substituting, $I$ is in A and $U$ is in V:

$$PCE = \frac{\Phi_e}{I \times U} \times 100\%$$(Formula 30)

The current efficiency CE is the ratio of luminance to current density, in cd/A:

$$CE = \frac{L_v}{J}$$(Formula 31)

The power efficiency PE is the ratio of the total luminous flux to the electrical power, in lm/W:

$$PE = \frac{\Phi_v}{I \times U}$$(Formula 32)

5 Correspondence Between Calculation Results and ElectronView Software

All the calculation formulas above are built into the ElectronView optoelectronic test software, which automatically completes the closed loop of "acquisition — calibration — solving — plotting". This chapter reviews the calculation chain and establishes the correspondence between the formula results and the software output, so that experimenters can understand the data sources against the software interface.

5.1 Review of the Calculation Chain

For a complete EQE test, the data flow is as follows: the spectrometer acquires AD counts, which are corrected by the radiometric calibration coefficients to obtain the spectral radiant flux $\Phi_{e,\lambda}$ (optical power distribution plot); the source meter simultaneously provides the voltage $U$ and current $I$. From $\Phi_{e,\lambda}$, the radiant flux (Formulas 13, 14), luminance (Formulas 15-18) and radiance (Formulas 19, 20) are solved in sequence; then the EQE is solved together with the current (Formulas 21-25); the chromaticity module calculates the tristimulus values and chromaticity coordinates from the radiant flux (Formulas 26-29); and the efficiency parameters PCE, CE and PE are obtained from Formulas 30-32.

5.2 Correspondence Between Formulas and Software Output

Calculation result (OUTPUT) Based on formula Corresponding output location in ElectronView
Optical power distribution / radiant flux Formulas 13, 14 Spectral module "Power" mode, Y-axis in μW
Current density J-V curve ($J = I/A$) — J-V curve plotted in real time by the EQE module
Luminance Formulas 15-18 L-J curve and luminance result in the EQE module
Radiance Formulas 19, 20 Radiance-related result display
External quantum efficiency EQE Formulas 21-25 EQE module solution result (exportable as CSV)
CIE chromaticity coordinates (x, y) Formulas 26-29 Color coordinates output in real time by the chromaticity calculation module
PCE / CE / PE Formulas 30-32 Efficiency parameters in the results table
Lifetime T50 / T70 — LED lifetime test module, which stops automatically at the decay-percentage threshold and records the result

5.3 Obtaining the Software

The ElectronView Professional software is permanently free for customers who purchase quantum efficiency measurement systems from Pynect, and other users can try it free for 90 days. It can be downloaded from the official website: ElectronView software download; for the specific operation of the software, see ElectronView electroluminescence quantum efficiency measurement software tutorial.

References

Textbooks

  1. Jin Weiqi, Wang Xia, Liao Ningfang, Huang Qingmei. Radiometry, Photometry and Colorimetry and Their Measurement (2nd Edition). Beijing: Beijing Institute of Technology Press.

National Standards

  1. GB/T 26179-2010 Spectroradiometric measurement of light sources
  2. GB/T 26178-2010 Method of measurement of luminous flux
  3. GB/T 7922-2023 Method of measurement of the color of illuminating light sources
  4. GB/T 3977-2008 Specification of colors
  5. GB/T 3978-2008 Standard illuminants and geometric conditions

International Standards (CIE / ISO)

  1. CIE 015:2018 Colorimetry, 4th Edition
  2. ISO/CIE 23539:2023 Photometry — The CIE system of physical photometry
  3. ISO/CIE 11664-1:2019 Colorimetry — Part 1: CIE standard colorimetric observers
  4. CIE 250:2022 Spectroradiometric measurement of optical radiation sources
  5. CIE 84:1989 The measurement of luminous flux
  6. CIE S 025:2015 Test method for LED lamps, LED luminaires and LED modules

Document version v1.3 (August 23, 2026). Authors: Wenyuan Ou, Yujie Shen.