Technical Background of This Article This article is written by the Leader Lighting Technical R&D Team and reviewed by Founder Chang Yaohui. Leader Lighting has been deeply engaged in LED phosphor manufacturing for over 15 years, holding more than 10 invention patents, and maintaining strategic cooperation with Tsinghua University and the Chinese Academy of Sciences. All parameter data in this article comes from the company's official product specification sheets, covering 39 commercial models across LD series, LDS series, and LDE series, all traceable item by item.
Why is red phosphor selection for plant lighting different?
The core difference between plant lighting and ordinary commercial lighting is: light is the "food" for plants, not just for human visual needs.
Chlorophyll's photosynthesis absorption peaks are concentrated in two bands—440nm blue light and 660nm red light. Among them, 660nm red light directly drives photosynthesis efficiency and is the "staple food" of plant lighting. Far-red light around 730nm regulates photomorphogenesis, affecting stem elongation, flowering induction, and circadian rhythms.
However, there is a key understanding: nitride red phosphors (Eu²⁺ activated) are inherently broad band emission materials, with FWHM typically between 74-90nm. This is completely different from the narrow band characteristics of KSF fluorides (Mn⁴⁺ activated, FWHM ≤ 10nm).
So the question arises: Can broad band nitride red phosphors be used for plant lighting? How to select to maximize photosynthetic efficiency in the 660nm band?
Core task of this article: To help plant lighting engineers and procurement personnel correctly understand the spectral characteristics of nitride red phosphors, and complete 660nm red light and far-red phosphor selection decisions based on real product parameters.
1. First, clarify a common misconception: Nitride red phosphor is not a narrow band material
1.1 Emission mechanism determines spectral width
Nitride red phosphors use Eu²⁺ as the activator ion, and their 4f-5d transitions have parity-allowed characteristics, resulting in naturally broad emission spectra. In Leader Lighting's product line, the Full Width at Half Maximum (FWHM) of LD series nitride red phosphors is concentrated in the 74-90nm range.
For truly narrow band red light (FWHM ≤ 10nm), Mn⁴⁺ activated KSF fluoride systems should be considered—but this is not within the scope of this article.
1.2 Broad band ≠ unsuitable for plant lighting
Although nitride red phosphors are broad band materials, by selecting models with peak wavelengths precisely at 660nm, we can still ensure that most light energy covers the sensitive range of plant photosynthesis (640-680nm). The advantages of broad band include:
- Covers a wider red light band, addressing the absorption needs of different photosynthetic pigments
- Compatible with high CRI lighting formulations, suitable for plant viewing scenarios where human eye comfort is also considered
- Better batch stability and larger process tolerance
2. Two key red light bands for plant lighting
2.1 660nm red light: Core driver of photosynthesis
660nm is the absorption peak of chlorophyll a, where photosynthesis efficiency reaches its highest. Key points to focus on during selection:
- Peak wavelength: 660nm ± 3nm
- Full Width at Half Maximum: typically 85-90nm for nitride systems
- Color coordinates: CIEx 0.68-0.69 range
2.2 678nm far-red light: Regulatory switch for photomorphogenesis
Far-red light (700-750nm, commonly 678-730nm in practice) regulates plant morphogenesis through phytochrome:
- Promotes stem elongation: increasing far-red proportion can accelerate plant height growth
- Induces flowering: long-day plants are sensitive to far-red light
- Regulates circadian rhythms: affects plants' "biological clock"
3. 660nm red phosphor selection: Precise matching based on real parameters
Based on Leader Lighting's product line, the following models are available for the 660nm band:
| Model | Peak Wavelength | FWHM | D50(μm) | CIEx/CIEy | Application Scenario |
|---|---|---|---|---|---|
| LD-660S | 660nm | 89nm | 5.0 | 0.6871/0.3126 | Fine particle size, thin glue layer SMD packaging |
| LD-660F | 663nm | 90nm | 10.0 | 0.6844/0.3152 | General COB/SMD packaging |
| LD-660D | 660nm | 88nm | 13.0 | 0.6882/0.3115 | Medium particle size, general packaging |
| LD-660B | 660nm | 90nm | 15.0 | 0.6859/0.3138 | Standard particle size, conventional application |
| LD-660FD | 658nm | 88nm | 24.0 | 0.6895/0.3103 | Coarse particle size, thick glue layer packaging |
Data source: Leader Lighting official product parameter table, batch traceable
Selection decision logic
Core understanding: The FWHM of the above models are all in the 88-90nm range, with similar spectral characteristics. The core variables for selection are particle size (D50) and peak wavelength, not FWHM.
Scenario 1: Thin glue layer SMD packaging (glue layer thickness < 100μm)
- Recommended model: LD-660S (D50 = 5.0μm)
- Reason: Fine particle size has good dispersibility, less prone to sedimentation, suitable for thin coatings and low-power packaging
Scenario 2: Conventional COB/SMD packaging
- Recommended models: LD-660F (D50 = 10.0μm) or LD-660D (D50 = 13.0μm)
- Reason: Medium particle size, strong versatility, suitable for most packaging processes
Scenario 3: Thick glue layer or remote phosphor structure
- Recommended model: LD-660FD (D50 = 24.0μm)
- Reason: Coarse particle size has controllable distribution in thick glue layers, suitable for remote phosphor design
Peak wavelength fine-tuning:
- Precise 660nm requirement: choose LD-660S, LD-660D, LD-660B
- Slightly deeper red (663nm): choose LD-660F
- Slightly shallower (658nm): choose LD-660FD
4. Far-red phosphor selection: 678nm solution detailed explanation
| Model | Peak Wavelength | FWHM | D50(μm) | CIEx/CIEy | Application Scenario |
|---|---|---|---|---|---|
| LD-680A | 678nm | 90nm | 15.0 | 0.7031/0.2960 | Far-red regulation, flowering promotion |
| LD-670A | 667nm | 90nm | 10.0 | 0.6947/0.3050 | Deep red band, transitional application |
Data source: Leader Lighting official product parameter table
Far-red formulation suggestions
Far-red light is usually not used alone, but mixed with 660nm red light in proportion:
- Leafy vegetables rapid growth: 660nm as main, far-red proportion 5-10%
- Flowering promotion (long-day plants): far-red proportion can be increased to 15-20%
- Plant height regulation: increasing far-red proportion can promote stem elongation
LD-680A's 678nm peak wavelength with 90nm FWHM, its spectral tail can extend beyond 700nm, partially covering the effective far-red range.
5. Deep red band supplement: Special value of 650nm models
Some plant lighting solutions add 650nm deep red light to 660nm to broaden red light coverage and improve viewing comfort:
| Model | Peak Wavelength | FWHM | D50(μm) | CIEx/CIEy | Description |
|---|---|---|---|---|---|
| LD-650D | 650nm | 86nm | 15.0 | 0.6753/0.3245 | Deep red broad band |
| LD-650F | 653nm | 85nm | 15.0 | 0.6737/0.3260 | Deep red broad band |
| LD-650H | 653nm | 87nm | 14.0 | 0.6754/0.3241 | Deep red broad band |
Application scenarios: Plant viewing lighting (need to meet human eye comfort simultaneously), full-spectrum solutions that need to broaden red light coverage.
6. Material system and packaging process adaptation
6.1 Nitride system (LD series): First choice for plant lighting
All 660nm plant lighting models in the product line are nitride system (Sr,Ca)AlSiN₃:Eu, with the following advantages:
- Density 3.8 g/cm³: good suspension in packaging glue, uniform distribution
- High chemical stability: resistant to humidity and heat, good long-term reliability
- Wavelength precision ±1.0nm: excellent batch consistency
- Thermal stability: temperature resistance meets conventional 150℃ curing process
6.2 Particle size and packaging process matching
| Particle Size Range | Representative Models | Packaging Process Adaptation |
|---|---|---|
| 5-7μm | LD-660S, LD-660X | Fine particle size, thin glue layer SMD, low-power packaging |
| 10-15μm | LD-660F, LD-660D, LD-660B | Medium particle size, general COB/SMD packaging |
| 20-24μm | LD-660FD | Coarse particle size, thick glue layer, remote phosphor |
Process reminder: Particle size selection needs to match dispensing equipment. Fine particles (<10μm) have good dispersibility but tend to agglomerate, requiring sufficient grinding; coarse particles (>20μm) need attention to needle aperture and sedimentation control.
6.3 Excitation band matching
All models have excitation band of 450-460nm, fully compatible with mainstream InGaN blue LED chips in the market, no need to adjust chip procurement specifications.
7. Incoming inspection and formulation verification points
7.1 Key inspection items
| Inspection Item | Specification Requirement | Inspection Method | Judgment Basis |
|---|---|---|---|
| Emission Wavelength | Nominal value ±1.0nm | Fluorescence Spectrometer | Deviation >1.5nm requires re-inspection |
| Color Coordinates CIEx/CIEy | Nominal value ±0.003 | Colorimeter | Deviation >0.005 requires re-inspection |
| D50 Particle Size | Nominal value ±1.0μm | Laser Particle Size Analyzer | Deviation >2.0μm requires re-inspection |
| Appearance | No caking, no foreign matter | Visual inspection | Caking requires return |
7.2 Formulation adjustment suggestions
- Red phosphor addition ratio: In plant lighting, 660nm red phosphor usually accounts for 40-60% of total phosphor amount
- Red to blue ratio: For leafy vegetables, common R:B = 4:1 to 8:1; for fruits and vegetables, can be adjusted to 3:1
- Dispersion process: Three-roll grinding or high-speed dispersion is recommended to ensure uniform phosphor distribution
7.3 Batch stability verification
It is recommended to request CoA reports for the past 3-6 batches and calculate CPK values for peak wavelength and color coordinates:
| CPK Range | Conclusion |
|---|---|
| CPK ≥ 1.33 | ✅ Production line controlled, can be safely introduced |
| CPK 1.0~1.33 | ⚠️ Recommended to increase incoming inspection frequency |
| CPK < 1.0 | ❌ Supplier stability questionable, introduce with caution |
🔬 Need plant lighting sample verification?
Leader Lighting provides special support for plant lighting applications:
- Free samples: LD-660S/D/F/B and LD-680A models provide 10-20g free samples
- Batch CoA: Each batch provides measured reports of key parameters including peak wavelength, color coordinates, FWHM
- Thermal stability testing: Provides 300°C thermal stability test data to support high-power packaging reliability verification
8. FAQ
9. About Leader Lighting
| Production Scale | R&D Team | Patents & Certifications |
|---|---|---|
| 15,000㎡ manufacturing base 5,000㎡ clean workshop Monthly capacity 10 tons |
25+ engineers Including 5 senior researchers with 10+ years experience Equipped with XRD, SEM, PL spectrometer |
10+ invention patents Passed SGS certification and RoHS compliance Full traceable CoA for each batch |
Strategic cooperation: Maintains long-term research cooperation with Tsinghua University and Chinese Academy of Sciences
Technical advisor: Professor Anatoly Vishnyakov, structural chemistry professor at Mendeleev University of Chemical Technology of Russia, author of over 300 academic papers
Service scope: Products exported to Asia, Europe, North America, serving global customers for over 15 years
References
- Leader Lighting Official Product Parameter Table (39 commercial models, including full LD/LDS/LDE series)
- Plant photosynthesis spectral response curve (McCree curve)
- Comparison of emission mechanisms between Eu²⁺ and Mn⁴⁺ activated phosphors