Trend AnalysisChemistry & Materials

Cadmium-Free Quantum Dot LEDs: The Future of Display Technology

Quantum dot LEDs (QLEDs) offer saturated colours, wide colour gamut (>140% sRGB), and high efficiency โ€” qualities that position them as successors to OLEDs for next-generation displays. But the best-p...

By Sean K.S. Shin
This blog summarizes research trends based on published paper abstracts. Specific numbers or findings may contain inaccuracies. For scholarly rigor, always consult the original papers cited in each post.

The Question

Quantum dot LEDs (QLEDs) offer saturated colours, wide colour gamut (>140% sRGB), and high efficiency โ€” qualities that position them as successors to OLEDs for next-generation displays. But the best-performing quantum dots are cadmium-based (CdSe), and the EU's RoHS directive restricts cadmium in electronics. Indium phosphide (InP) QDs are the leading cadmium-free alternative, but their efficiency has historically lagged CdSe by 30โ€“50%. Can InP QLEDs close this performance gap and enable the transition to heavy-metal-free displays?

Landscape

Bian et al. (2024) in Nature, achieved a breakthrough in green InP-based QLEDs by controlling electron injection and leakage. The key problem in InP QLEDs: ZnO electron transport layers inject electrons too aggressively, creating charge imbalance that causes Auger recombination (non-radiative quenching). By engineering an interlayer that moderates electron injection rate, they achieved external quantum efficiency (EQE) approaching that of CdSe QLEDs. This Nature publication signals that InP QLEDs have crossed a critical performance threshold.

Ali et al. (2025) reviewed recent progress in InP QD synthesis and QLED architecture, documenting the evolution from early core-only InP QDs to advanced core/shell/shell structures (InP/ZnSeS/ZnS). As described in the full paper, shell engineering has reportedly pushed quantum yields from modest early values to above 95% in optimised structures. The shell engineering controls surface defects that otherwise trap charge carriers and reduce luminescence.

Kwak et al. (2025) addressed charge balance from the device architecture side, modifying the inverted QLED stack to reduce electron-hole imbalance without sacrificing brightness. S. Li et al. (2025) demonstrated top-emission cadmium-free QLEDs โ€” important for microdisplay applications (AR/VR) where light must emit upward through the device stack.

Key Claims & Evidence

<
ClaimEvidenceVerdict
InP QLEDs approach CdSe QLED efficiencyElectron injection control achieves near-parity EQE (Bian et al. 2024)Confirmed; a watershed moment for cadmium-free displays
Core/shell engineering reportedly achieves high quantum yield in InP QDsInP/ZnSeS/ZnS structures reviewed (Ali et al. 2025)Supported; shell composition and thickness are critical
Charge imbalance is the primary efficiency limiterElectron overflow causes Auger quenching (Bian et al. 2024; Kwak et al. 2025)Well-established; addressed by transport layer engineering
Top-emission cadmium-free QLEDs are feasible for microdisplaysDemonstrated with competitive brightness (S. Li et al. 2025)Demonstrated; lifetime data needed for commercial viability

Open Questions

  • Blue InP QLEDs: Green and red InP QLEDs have reached high efficiency, but blue InP QDs are challenging (wide bandgap requires very small cores with high surface-to-volume ratios). Can blue InP match CdSe blue performance?
  • Operational lifetime: CdSe QLEDs achieve >100,000 hours at display brightness. InP QLEDs currently reach ~10,000โ€“50,000 hours. Can lifetime be extended to commercial requirements?
  • Patterning: QLED displays require patterned RGB sub-pixels. Can inkjet printing or photolithographic patterning of InP QDs achieve the resolution needed for high-PPI displays?
  • Cost: InP QD synthesis is more complex than CdSe. Can manufacturing scale-up reduce InP QD cost to compete with OLED emitters?

    • Referenced Papers

    • [1] Bian, Y. et al. (2024). Efficient green InP-based QD-LED by controlling electron injection and leakage. Nature. DOI: 10.1038/s41586-024-08197-z
    • [2] Ali, A. et al. (2025). Recent Progress in InP Quantum Dots and QLEDs. Laser & Photonics Reviews. DOI: 10.1002/lpor.202501169
    • [3] Kwak, H.J. et al. (2025). Balancing Charge Injection in Inverted InP QLEDs. Advanced Quantum Technologies. DOI: 10.1002/qute.202500182
    • [4] Li, S. et al. (2025). Top Emission LED Based on Cadmium-Free Quantum Dots. SID Symposium Digest. DOI: 10.1002/sdtp.18881
    • [5] Chen, Y. & Chung, S.-R. (2025). ZnInP/ZnS QDs for Display Applications. Proc. SPIE. DOI: 10.1117/12.3063896

    References (5)

    Bian, Y., Yan, X., Chen, F., Li, Q., Li, B., Hou, W., et al. (2024). Efficient green InP-based QD-LED by controlling electron injection and leakage. Nature, 635(8040), 854-859.
    DOIScholar
    Ali, A., Hussain, I., Seo, H., Park, J., Oh, S., Oh, D. Y., et al. (2025). Exploring the Recent Progress in InP Quantum Dots and QLEDs: Advances in Synthesis, Architecture, and Applications. Laser & Photonics Reviews, 19(22).
    DOIScholar
    Kwak, H. J., Jeong, J., Kiguye, C., Jang, S. H., Jeong, J. Y., & Kim, J. Y. (2025). Balancing Charge Injection for Enhanced Efficiency in Inverted InP Quantum Dot Lightโ€Emitting Diodes. Advanced Quantum Technologies, 8(10).
    DOIScholar
    Li, S., Li, D., Chen, Z., & Li, Y. (2025). 69โ€1: Efficient Top Emission Lightโ€Emitting Diode Based on Cadmiumโ€Free Quantum Dots. SID Symposium Digest of Technical Papers, 56(S1), 610-612.
    DOIScholar
    Chen, Y. H., & Chung, S. (2025). Effect of stirring speed on the size distribution and optical properties of ZnInP/ZnS quantum dots. Low-Dimensional Materials and Devices 2025, 25.
    DOIScholar

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