Photoluminescence Quantum Yield (PLQY) Measurement: Principle, Methods, and System

Abstract

The photoluminescence quantum yield (PLQY) is the core parameter characterizing the photon conversion efficiency of luminescent materials, defined as the ratio of photons emitted by the material to photons absorbed by it. Accurate PLQY measurement is indispensable for research and quality control of OLED emissive materials, perovskite nanocrystals, quantum dots, fluorescent probes, and upconversion materials. Starting from the fundamentals of photophysics, this article systematically explains the radiometric calibration principle and the photon-number calculation method, compares in depth the measurement strategies and applicable scenarios of the absolute method (two-step method) and the relative method, details the hardware composition and software architecture of a typical PLQY measurement system, and thoroughly analyzes key influencing factors such as self-absorption, re-excitation, oxygen quenching, and temperature effects together with their experimental countermeasures. Finally, combined with cutting-edge techniques such as the photothermal threshold quantum yield (PTQY) method and relevant measurement standards, it looks ahead to the development of PLQY measurement technology.

1. Introduction

1.1 Physical Definition of PLQY

When a luminescent material absorbs a photon, an electron transitions from the ground state to an excited state. The excited-state molecule returns to the ground state through two competing pathways: radiative transitions (emitting fluorescence or phosphorescence) and non-radiative transitions (internal conversion, intersystem crossing, vibrational relaxation, etc.). The photoluminescence quantum yield quantitatively describes the proportion of radiative transitions among all de-excitation processes, and is mathematically defined as:

$$\Phi = \frac{N_{\text{em}}}{N_{\text{abs}}}$$

where:
- $N_{\text{em}}$ — the total number of photons emitted by the material;
- $N_{\text{abs}}$ — the total number of excitation photons absorbed by the material;
- $\Phi$ ranges from $0 \sim 1$ (i.e., $0\% \sim 100\%$).

1.2 Physical Significance and Importance of PLQY

The value of PLQY directly reflects the fraction of excited-state energy used for emission. The closer $\Phi$ is to 1, the more the radiative recombination rate exceeds the non-radiative recombination rate, and the better the material's luminescence performance; a decrease in $\Phi$ points to the presence of non-radiative loss channels such as lattice defects, surface dangling bonds, impurity quenching, or Auger recombination.

From a photophysics standpoint, the relationship between PLQY and the radiative rate constant $k_r$ and the non-radiative rate constant $k_{nr}$ is:

$$\Phi = \frac{k_r}{k_r + k_{nr}}$$

This relation reveals the deeper significance of PLQY measurement: by measuring $\Phi$ and combining it with the fluorescence lifetime $\tau = 1/(k_r + k_{nr})$, $k_r$ and $k_{nr}$ can be solved separately, providing deeper insight into the luminescence dynamics of the material.

1.3 Difference Between PLQY and EQE

PLQY (photoluminescence quantum yield) and EQE (external quantum efficiency) both belong to the category of quantum efficiency, but differ markedly in measurement object and excitation mode:

Dimension PLQY EQE
Excitation mode Optical excitation Electrical injection
Measurement object The luminescent material itself (film, solution, powder) The complete device (including electrodes and transport layers)
Physical meaning Absorbed photon → emitted photon Injected electron → output photon
Limiting factors Competition between $k_r$ and $k_{nr}$ Injection efficiency × radiative recombination efficiency × light extraction efficiency
Typical values (PeLED) > 80% 15%–26%

High PLQY is a necessary but not sufficient condition for obtaining a high-EQE device — going from material to device still requires overcoming multiple engineering challenges such as charge-injection balance, exciton confinement, and light extraction efficiency.

2. Radiometric Calibration Principle

2.1 Why Radiometric Calibration Is Needed

In actual measurements, the spectrometer detector (such as a CCD, CMOS, or InGaAs linear array) outputs counts corresponding to photon events, rather than absolute optical power. Because the detector's quantum efficiency, grating diffraction efficiency, and optical element transmittance are all wavelength-dependent, the same photon flux can produce very different count values at different wavelengths. Therefore, to obtain absolute spectral radiant power, the spectrometer system must undergo radiometric calibration to establish a "counts → optical power" mapping at every wavelength.

2.2 Derivation of the Calibration Coefficient $f(\lambda)$

The basic method of radiometric calibration is to use a standard light source with known spectral radiant power (such as a tungsten-halogen standard lamp traceable to NIST or the National Institute of Metrology of China). Let the known spectral radiant power of the standard source at wavelength $\lambda$ be $I_0(\lambda)$ (unit: W/nm), and the relative intensity (counts) measured by the spectrometer over integration time $t_0$ be $S_0(\lambda)$. Then the radiometric calibration coefficient $f(\lambda)$ is defined as:

$$f(\lambda) = \frac{I_0(\lambda)}{S_0(\lambda)} \times t_0$$

The physical meaning of this coefficient is: the absolute optical power corresponding to each count value at an integration time of 1 s (unit: W/count).

Key insight: As long as the optical-path components — spectrometer, fiber, integrating-sphere port, etc. — remain unchanged, $f(\lambda)$ is a constant, and a single calibration can be used for a long time. However, after replacing a fiber, grating, or slit, or after the system has been transported and subjected to mechanical shock, recalibration is mandatory.

2.3 Conversion from Counts to Optical Power

Once the calibration coefficient $f(\lambda)$ is obtained, for any light source under test, set the integration time $t$ and measure its relative spectrum $S(\lambda)$. The absolute optical power distribution $I(\lambda)$ is then obtained by:

$$I(\lambda) = f(\lambda) \times \frac{S(\lambda)}{t}$$

Remember this core concept: all subsequent photometric, radiometric, and colorimetric quantities, as well as derived parameters such as EQE and PLQY, originate from the optical power distribution curve $I(\lambda)$.

3. Photon Number Calculation

3.1 Single-Photon Energy

Since PLQY is essentially a ratio of photon numbers rather than a ratio of optical powers, optical power must be converted to photon number. According to the Planck relation, the energy of a single photon at wavelength $\lambda$ is:

$$E(\lambda) = \frac{hc}{\lambda}$$

where $h = 6.62607015 \times 10^{-34}$ J·s is the Planck constant and $c = 2.99792458 \times 10^8$ m/s is the speed of light in vacuum.

3.2 Photon Number Density and Total Photon Number

For an integration time $t = 1$ s, the number of photons $N(\lambda)$ emitted by monochromatic light of wavelength $\lambda$ within a unit wavelength interval is:

$$N(\lambda) = \frac{I(\lambda)}{hc} \lambda$$

The physical meaning of the above formula is the number of photons emitted by the source within a unit wavelength interval at wavelength $\lambda$ during 1 s.

For the total photon number within a waveband $[a, b]$, use discrete summation (since spectrometer pixels are discretely distributed):

$$N_t = \sum_{\lambda = a}^{b} N(\lambda) \, \Delta\lambda = \frac{1}{hc} \sum_{\lambda = a}^{b} I(\lambda) \, \lambda \, \Delta\lambda$$

where $\Delta\lambda$ is the wavelength interval corresponding to a spectrometer pixel.

4. PLQY Measurement Methods

4.1 Absolute Method (Two-Step Method)

The absolute method directly uses a radiometrically calibrated spectral system to determine the number of photons absorbed and emitted by the sample, and calculates the absolute PLQY from the definition. The two-step method is the most classical and reliable absolute-method measurement procedure.

Measurement Steps

Step a — blank measurement:

Place the blank solvent or blank substrate (without the luminescent material under test) at the sample position of the integrating sphere, and collect only the scattered spectrum of the excitation light within the sphere, recorded as the excitation reference spectrum $E_a(\lambda)$. At this point, all the signal received by the detector comes from unabsorbed scattered excitation light.

Step b — sample measurement:

Place the sample under test at the sample position of the integrating sphere and obtain two spectra simultaneously:
- Scattered excitation spectrum $E_b(\lambda)$: the remaining scattered excitation light after absorption by the sample;
- Emission spectrum $P(\lambda)$: the fluorescence/phosphorescence spectrum emitted by the sample upon excitation.

Calculation

The sample's absorbance $A$ (the integral over the excitation wavelength):

$$A = 1 - \frac{\int_{\text{exc}} E_b(\lambda) \, d\lambda}{\int_{\text{exc}} E_a(\lambda) \, d\lambda}$$

Calculation of PLQY:

$$\Phi = \frac{\int_{\text{em}} P(\lambda) \, d\lambda}{\int_{\text{exc}} [E_a(\lambda) - E_b(\lambda)] \, d\lambda}$$

where "exc" denotes the excitation-wavelength integration interval and "em" denotes the emission-wavelength integration interval. $E_a - E_b$ is the number of excitation photons actually absorbed by the sample (after photon-number conversion).

Note: In the above formulas, $E_a$, $E_b$, and $P$ all refer to photon-number integrals after radiometric calibration and photon-number conversion, not the raw count values. In practical software implementation, the three-step conversion $S(\lambda) \to I(\lambda) \to N(\lambda)$ must be performed first.

4.2 Relative Method

The relative method determines the PLQY of the sample under test by comparing it with a standard reference of known PLQY. Its core formula is:

$$\Phi_x = \Phi_{\text{std}} \cdot \frac{F_x}{F_{\text{std}}} \cdot \frac{A_{\text{std}}}{A_x} \cdot \frac{n_x^2}{n_{\text{std}}^2}$$

where:
- $\Phi_x$, $\Phi_{\text{std}}$ — the PLQY of the sample under test and the standard sample;
- $F_x$, $F_{\text{std}}$ — the integrated emission intensities of the sample under test and the standard sample;
- $A_x$, $A_{\text{std}}$ — the absorbances of the sample under test and the standard sample at the excitation wavelength;
- $n_x$, $n_{\text{std}}$ — the refractive indices of the solvents used for the sample under test and the standard sample.

The refractive-index correction term $n_x^2 / n_{\text{std}}^2$ arises from the difference in the collection solid angle of emitted light in different solvents — in a high-refractive-index solvent, more emitted light is confined within the sample cell by total internal reflection, reducing the number of photons actually collected by the integrating sphere.

Common Standard References

Standard PLQY Solvent / Conditions
Quinine sulfate 0.55 ± 0.05 0.1 M H₂SO₄
Rhodamine 6G 0.95 Ethanol
Fluorescein 0.93 0.1 M NaOH
Rhodamine B 0.65 Ethanol
IR-26 0.0005–0.0050 (highly disputed) 1,2-dichloroethane

It should be particularly noted that the PLQY of organic fluorophores in the NIR-II region (1000–1700 nm) is usually very low (< 1%). When IR-26 is used as a standard, the systematic error introduced cannot be ignored because the reported literature values differ by an order of magnitude (0.05%–0.50%). In 2025, Shen et al. proposed TPE-BBT (PLQY = 3.94% in THF) as a more reliable relative-method standard for the NIR-II region.

4.3 Comparison of the Two Methods

Item Absolute method (two-step) Relative method
Requires a standard sample? No Yes
Requires radiometric calibration? Yes No (can compare directly under identical conditions)
Applicable sample forms Liquid, film, powder Usually only liquid
Measurement accuracy High, but depends on calibration and system alignment Limited by the accuracy of the standard sample
Operational complexity Higher Lower
System cost Requires integrating sphere + calibration source Only a conventional fluorescence spectrometer
Preferred scenario New-material R&D, precise determination Rapid comparison, routine batch testing

Recommended strategy: For research-grade work, prefer the absolute method to obtain traceable absolute PLQY values; in scenarios with limited conditions or for rapid batch evaluation, the relative method still retains practical value through its simple operation.

5. Typical PLQY Measurement Systems

The core architecture of a complete PLQY measurement system is: excitation source → integrating sphere (sample chamber) → spectrometer → data-processing unit. Depending on how the excitation source is implemented, there are currently two main typical system schemes.

5.1 Scheme 1: Monochromatic LED / Laser Excitation

Using a monochromatic LED or semiconductor laser directly as the excitation source, together with a narrow-band filter to further purify the excitation light, is the simplest and most efficient PLQY measurement scheme.

System Architecture

Monochrome LED / LD → narrow-band filter → integrating sphere (sample position) → optical fiber → array spectrometer → host computer

Core Components

  • Excitation source: Commonly used center wavelengths include 365 nm, 405 nm, 450 nm, and 520 nm monochromatic high-power LEDs, or semiconductor lasers (LDs) at the corresponding wavelengths. LEDs are low-cost, long-lived, and have stable output; LDs provide higher power density and narrower linewidth (typically < 2 nm FWHM), making them suitable for measuring weakly emissive materials. The excitation wavelength should be chosen within the sample's absorption band and separated from the emission peak by sufficient spectral distance (typically > 30 nm) to prevent the excitation scattering peak from interfering with the emission spectrum.
  • Narrow-band filter: Placed in the excitation path to further suppress the sideband emission and stray light of the LED/LD and ensure the monochromaticity of the excitation light.
  • Integrating sphere: Inner diameter typically 38–150 mm, with a sintered high-purity PTFE inner wall whose diffuse reflectance in the visible–near-infrared band exceeds 98%. It features an excitation entrance port, a sample port, and a light-collection port (standard SMA905 interface).
  • Array spectrometer: Cooled back-illuminated CCD covering 350–1100 nm. A single exposure captures the complete spectrum without mechanical scanning, significantly shortening the time per measurement.

Advantages and Limitations

Advantages Limitations
Compact structure, simple optical path, low cost Excitation wavelength fixed (depends on LED/LD specifications)
High excitation power density, good signal-to-noise ratio Cannot continuously scan excitation-wavelength dependence
Easy to integrate into confined spaces such as glove boxes Changing the excitation wavelength requires replacing the source hardware
Good optical-path stability, high repeatability Limited wavelength options in the deep-UV region (< 350 nm); covering multiple UV excitation needs with single-wavelength sources requires multiple units, raising cost

Applicable scenarios: routine PLQY determination, batch quality control at a fixed excitation wavelength, and in-situ/glove-box environment measurements.

5.2 Scheme 2: Xenon Lamp + Monochromator for Monochromatic Excitation

Using a broadband xenon lamp together with a monochromator (grating dispersion) to select monochromatic light of any wavelength from the continuous spectrum as the excitation source is the most flexible and fully-featured PLQY measurement scheme.

System Architecture

Xenon lamp → monochromator (entrance slit + grating + exit slit) → integrating sphere (sample position) → optical fiber → array spectrometer → host computer

Core Components

  • Excitation source: A 150 W or 300 W high-pressure short-arc xenon lamp, providing continuous and stable spectral output over 250–700 nm (extendable to the near-infrared). The xenon lamp must be fully warmed up (20–30 minutes) to reach thermal equilibrium before use.
  • Monochromator: Usually a Czerny-Turner optical layout, continuously selecting the output wavelength by rotating the grating angle. Key parameters include the grating ruling density (determining resolution and wavelength range) and the entrance/exit slit widths (determining the balance between excitation bandwidth and throughput, with a typical bandwidth of 2–5 nm FWHM).
  • Integrating sphere: Same as Scheme 1, but with an additional xenon-lamp focusing/coupling optics assembly (lens group or off-axis parabolic mirror).
  • Array spectrometer: Same as Scheme 1.

Advantages and Limitations

Advantages Limitations
Excitation wavelength continuously tunable, highly flexible Complex optical path, larger system footprint
Can measure the excitation-wavelength-dependent PLQY spectrum Monochromator output power far lower than LED/LD
A single instrument covers multiple material systems High optical alignment precision required, high maintenance cost
UV–near-infrared coverage via grating replacement UV-band throughput decays quickly; the xenon lamp requires periodic replacement

Applicable scenarios: excitation-wavelength optimization of PLQY in new-material R&D, multi-wavelength PLQY characterization, and materials requiring UV excitation (such as wide-bandgap semiconductors and rare-earth upconversion materials).

5.3 Selection Guidance for the Two Schemes

Selection dimension Scheme 1 (LED/LD excitation) Scheme 2 (xenon lamp + monochromator)
Excitation-wavelength flexibility Fixed, requires hardware change Continuously tunable, software-controlled
Excitation optical power High (tens of mW) Low (μW level)
System complexity Low High
System footprint Compact, can fit in a glove box Larger
Wavelength-dependent PLQY Requires combining multiple sources One-click scan
Cost Low High
Preferred application Routine determination at a fixed wavelength, online QC New-material R&D, excitation-wavelength optimization

5.4 Key Modules Shared by Both Schemes

Regardless of the excitation scheme adopted, the following modules are standard for a PLQY measurement system:

  • Radiometric calibration source: A traceable tungsten-halogen standard lamp used for absolute spectral-response calibration of the system. The lamp current must be set strictly to the value on the calibration certificate. It is recommended to send the standard lamp for verification or replacement after more than 500 hours of cumulative use.
  • Spectrometer: Cooled back-illuminated CCD (detector temperature at least 20°C below ambient), 16-bit ADC, dark noise < 50 counts (at 100 ms integration time), signal-to-noise ratio > 1000:1, optical resolution better than 2.5 nm (FWHM).
  • Integrating sphere: Sintered high-purity PTFE lining, UV-Vis-NIR reflectance > 98%, total port area not exceeding 5% of the sphere's inner surface area, with a baffle to shield first-bounce reflected light.
  • Fiber and interfaces: Standard SMA905 interface, 200–1000 μm core, ensuring mechanical alignment consistency across repeated plug/unplug cycles.
  • Measurement software: Integrates radiometric calibration, the two-step measurement procedure, photon-number conversion, and automatic PLQY calculation, and supports one-click measurement report generation. Scheme 2 additionally requires monochromator wavelength-scan control.

6. Key Factors Affecting PLQY Measurement Accuracy

6.1 Self-Absorption

Cause: When the sample concentration is high or the optical path is long, emitted short-wavelength fluorescence is re-absorbed by the sample itself before leaving it — because the absorption and emission spectra have an overlapping region (the smaller the Stokes shift, the larger the overlap).

Typical manifestations:
- A dip or shape distortion on the short-wavelength side of the emission spectrum
- The PLQY of the same sample measured at different concentrations declines systematically as concentration increases
- Red shift of the emission peak (short-wavelength components are preferentially absorbed)

Solutions:
1. Dilution (preferred): dilute the sample stepwise and extrapolate to the zero-concentration limit
2. Thin-layer sample preparation: uniformly disperse the powder in an inert BaSO₄ matrix and press into a pellet to reduce the optical path
3. Mathematical correction: the Mével iterative method estimates self-absorption loss based on the overlap integral of the absorption and emission spectra

6.2 Re-excitation

Cause: After multiple diffuse reflections within the integrating-sphere cavity, fluorescence emitted by the sample may strike the sample again and be absorbed, exciting additional fluorescence. This cascade process inflates the emitted photon count and overestimates the PLQY.

Judgment indicator: If the PLQY of the same sample measured at different excitation powers increases with power, or if the PLQY measured in a low-reflectance integrating sphere is markedly lower than in a high-reflectance sphere, re-excitation may be present.

Mitigation measures: lower the excitation power, or use an integrating sphere with moderately reduced inner-wall reflectance (trading off some signal-to-noise ratio).

6.3 Oxygen Quenching

Mechanism: Ground-state molecular oxygen (³O₂) is a highly effective fluorescence quencher that can deactivate excited states non-radiatively through energy transfer or electron transfer. Its effect is especially pronounced for phosphorescent materials (where triplet states participate in emission) and thermally activated delayed fluorescence (TADF) materials.

Countermeasures:
- Measure in an inert-atmosphere glove box (N₂ or Ar, O₂ < 1 ppm)
- Bubble liquid samples with high-purity N₂/Ar for 15–30 minutes to remove oxygen, then measure in a sealed cuvette
- Verify oxygen sensitivity through air-vs-inert-atmosphere comparison experiments

6.4 Integrating-Sphere Spectral-Response Calibration

The inner-wall reflectance of the integrating sphere and the transmittance of the exit-port optical elements are both wavelength-dependent. Without system-wide radiometric calibration (integrating sphere + fiber + spectrometer), optical power at different wavelengths will be systematically overestimated or underestimated. Performing full-wavelength system-level calibration with a traceable standard source is the prerequisite for accurate PLQY measurement.

6.5 Other Influencing Factors

  • Temperature: rising temperature enhances the non-radiative transition rate, lowering PLQY; for precision measurements, temperature control of ±1°C is recommended
  • Photostability: prolonged excitation may cause photobleaching/photodegradation; control the excitation intensity and irradiation time
  • Detector nonlinearity: keep the signal level within the detector's linear dynamic range (10%–90% of full scale)
  • Dark-noise subtraction: acquire a dark spectrum before each measurement, with the integration time and number of averages identical to the sample measurement
  • Correct selection of integration regions: the boundaries of the excitation and emission regions should avoid overlap and cross-interference

7. Sample Preparation Guidelines

7.1 Liquid Samples

  • Use high-transmittance, low-fluorescence quartz cuvettes; do not use ordinary glass (which produces background fluorescence under UV excitation)
  • Concentration optimization: keep the absorbance at 0.05–0.10 (at the excitation wavelength), balancing signal-to-noise ratio and self-absorption
  • Before each sample change, run a blank control with pure solvent to subtract solvent Raman scattering and background fluorescence
  • Wipe the outer walls of the cuvette clean; fingerprints and dust contamination scatter the excitation light

7.2 Solid Films

  • Films should be flat with uniform thickness, avoiding wrinkles and bubbles
  • Use a blank substrate (such as a clean quartz plate) as a control to ensure the substrate fluorescence has been subtracted
  • Face the film toward the excitation-light incidence direction and keep the mounting position consistent

7.3 Powder Samples

  • Grind thoroughly to ensure uniform particle size; large particles cause severe scattering
  • Use a powder-pressing fixture to create a flat measurement surface
  • Mix highly absorptive powders with an inert diluent (BaSO₄ / KBr) in proportion, grind, and press into pellets, then extrapolate on concentration
  • Note the consistency of the pressing pressure — different degrees of compaction affect the scattering fraction

8. Frontier Advances and Outlook

8.1 Photothermal Threshold Quantum Yield (PTQY)

In 2025, Schiettecatte et al. published the photothermal threshold quantum yield (PTQY) method in Chemistry of Materials — a new calorimetry-based technique for measuring the PLQY of QD solutions. Its core idea is to use the heat generated by non-radiative recombination to raise the solvent temperature, then infer the non-radiative transition energy through precision temperature measurement and combine it with the total absorbed energy to obtain the PLQY.

The unique advantage of PTQY is its extremely high accuracy for high-quantum-efficiency emitters ($\Phi \to 1$) and the fact that it requires no integrating sphere — bypassing the scattering-subtraction and re-excitation issues of the traditional absolute method. This method is particularly suited to certifying and benchmarking the emission efficiency of colloidal quantum dots.

8.2 Reliable PLQY Measurement in the NIR-II Region

The PLQY of fluorescent materials in the near-infrared II region (1000–1700 nm) is typically < 1%, and the measurement error of the traditional integrating-sphere method is significant. The TPE-BBT standard published in 2025 provides a more reliable option for relative-method PLQY measurement in the NIR-II region.

8.3 In-Situ / Multimodal Combination

  • Atmosphere/temperature in-situ PLQY: monitor quantum-yield changes in real time within a glove box or temperature-controlled chamber
  • Electroluminescence–photoluminescence combination: measure EQE and PLQY simultaneously to decouple device efficiency bottlenecks
  • Microscopic PLQY imaging: obtain quantum-yield distribution maps with micron-level spatial resolution

9. Relevant Standards

Standard Description
ISO 23584:2021 International standard for fluorescence quantum yield measurement
ASTM E2153-01(2021) Standard practice for determining quantum yield by fluorescence spectroscopy
GB/T 40292-2021 Photoluminescence quantum efficiency test method (Chinese national standard)
IEC 62607-3-1:2014 Nanomanufacturing — key control characteristics — Part 3-1: luminescent nanomaterials — quantum yield

10. Summary and Best Practices

Key Formula Quick Reference

Step Formula Description
Radiometric calibration $f(\lambda) = \frac{I_0(\lambda)}{S_0(\lambda)} t_0$ Establishes the counts → optical power mapping
Optical power conversion $I(\lambda) = f(\lambda) \cdot \frac{S(\lambda)}{t}$ Converts counts to absolute optical power
Photon number conversion $N(\lambda) = \frac{I(\lambda)}{hc} \lambda$ Converts optical power to photon number
Absolute-method PLQY $\Phi = \frac{\int P \, d\lambda}{\int (E_a - E_b) \, d\lambda}$ Core formula of the two-step method
Relative-method PLQY $\Phi_x = \Phi_{\text{std}} \cdot \frac{F_x}{F_{\text{std}}} \cdot \frac{A_{\text{std}}}{A_x} \cdot \frac{n_x^2}{n_{\text{std}}^2}$ Requires a standard + refractive-index correction

Best-Practice Checklist

  1. Radiometric calibration: use a fully warmed-up, traceable standard source; recalibration is mandatory after any change to the optical path
  2. Integration time: adjust so the spectral signal falls in the 100,000–200,000 counts range (16-bit ADC), avoiding saturation and under-exposure
  3. Self-absorption management: prefer diluting the sample or preparing a thin-layer sample; use concentration extrapolation when necessary
  4. Dark background and reference: re-acquire at each measurement sequence, keeping all measurement conditions consistent
  5. Integrating-sphere maintenance: protect from dust, liquid, and contact; clean the Spectralon® inner wall with compressed air and never use organic solvents
  6. Oxygen control: for oxygen-sensitive samples (phosphorescent, TADF materials), always measure in an inert atmosphere
  7. Data processing: rigorously subtract dark noise, correctly select integration regions, average multiple measurements, and report the standard deviation and measurement temperature
  8. System verification: periodically verify the system with standard fluorescent samples (Rhodamine 6G, sodium fluorescein) to ensure calibration remains valid

This article was compiled by Pynect, with references to the Feishu knowledge base, Chemistry of Materials (2025), Small (2025), and related vendor technical white papers.