What is Perovskite LED (PeLED)?
PeLEDs (Perovskite Light-Emitting Diodes) are LEDs that use metal halide perovskite materials as the emissive layer (EML). These perovskite materials have a specific structure defined by the formula ABX₃, where "A" is a monovalent cation (like Cs⁺, MA⁺, or FA⁺), "B" is a divalent cation (such as Pb²⁺ or Sn²⁺), and "X" is a halide ion (Cl⁻, Br⁻, or I⁻). PeLEDs are known for their excellent optoelectronic properties, including high photoluminescence quantum yield (PLQY), narrow emission spectrum, and solution-processability, making them promising for next-generation displays and lighting technologies.
Difference between PeLED and OLED
While OLEDs (Organic Light-Emitting Diodes) rely on organic materials for their emissive layers, PeLEDs use perovskite compounds. This key difference brings about various distinctions：
| Feature | PeLED | OLED |
|---|---|---|
| Emissive Materials | Uses metal halide perovskites (e.g., CsPbBr₃, MAPbBr₃). | Uses organic molecules or polymers (e.g., Ir(ppy)₃, Alq₃). |
| Emissive Layer Structure | ABX₃ structure, where A is a monovalent cation, B is a divalent metal, and X is a halide. | Composed solely of organic molecular layers, the layer structure is usually amorphous, not crystal lattice. |
| Light Emission Mechanism | The exciton is formed by current injection, and light emission relies on the recombination of the exciton in the emission layer. | The exciton is formed by current injection, and light emission relies on the recombination of the exciton in the emission layer. |
| Fabrication Method | Allows for low-cost solution processes like spin-coating and inkjet printing. | Requires multilayer organic material deposition, the depositions of these films are usually by vacuum process with higher cost. |
| Stability | Sensitive to moisture, oxygen, and UV light, prone to degradation. | Generally stable, though blue emitters have shorter lifespans. |
Advantages and Applications of PeLEDs
Advantages：
High Brightness and Efficiency：PeLEDs show excellent brightness and external quantum efficiency (EQE), particularly in the green and red wavelength ranges. Studies indicate PeLEDs can achieve EQEs of over 30% and brightness levels reaching up to 470,000 cd/m².
- Color Purity and Tunability: Perovskite materials allow precise bandgap tuning, resulting in high color purity, making PeLEDs ideal for high-quality color displays.
- Solution Processability: PeLEDs can be fabricated using cost-effective solution methods, such as spin-coating and inkjet printing, suitable for large-scale manufacturing.
Applications：
- High-Quality Displays: Due to their brightness and color purity, PeLEDs are well-suited for high-color-accuracy displays in televisions, smartphones, and premium display devices.
- Lighting Applications: PeLEDs’ high brightness makes them promising for next-generation lighting technologies, especially in the red and green light ranges.
Material Comparison
For PeLEDs:
-
Emissive Layer Materials：FAPbBr3, MAPbBr3, CsPbBr3, etc.
Function：These materials enable high-efficiency green and red emissions with excellent color purity, making them ideal for display functions. -
Electron Transport Layer (ETL) Materials：PO-T2T, 4PACz(dopant), PCBM, TPBi, PFN, Alq3, Bphen, B3PyPPM, B3PyMPM, TiO2, etc.
Function：Enhance electron injection and minimize recombination losses, improving the overall device efficiency. -
Hole Transport Layer (HTL) Materials：Poly-TPD, PVK, TFB, PEDOT:PSS, etc.
Function：Facilitate efficient hole transport and charge balance, leading to better performance and longer device lifespan.
For OLEDs:
-
Emissive Layer Materials：Ir(ppy)3, Alq3, TADF emitters, phosphorescent dyes
Function：Used in TVs, smartphones, and wearable devices for their bright colors and high efficiency. -
Electron Transport Layer (ETL) Materials：TPBi, Bphen, C60, etc.
Function：Improve electron mobility and device stability, reducing power consumption. -
Hole Transport Layer (HTL) Materials：Spiro-OMeTAD, NPB, PEDOT:PSS
Function：Enhance hole injection, improve device efficiency, and increase display brightness.
The Future Outlook
Both PeLEDs and OLEDs have promising futures. Due to its excellent flexibility and image quality, OLED has become mainstream in consumer electronics such as mobile phones, tablets, and televisions. PeLEDs, with their remarkable efficiency and tunable emissions, are emerging as a strong alternative. Research is ongoing to overcome PeLED stability issues and achieve efficient blue emissions, which could propel them into broader commercial adoption. With continued advancements, PeLEDs could play a significant role in next-generation displays, lighting, and beyond, potentially complementing or even rivaling OLEDs in the market.
Additional Reading
Lee, J., Xie, Z., Wang, L., & Hou, J. (2024). Advancements in Interfacial Engineering for Perovskite Light-Emitting Diodes. Chemistry – A European Journal, 30, e202400372.
Xiong, W., Tang, W., Zhang, G. et al. Controllable p- and n-type behaviours in emissive perovskite semiconductors. Nature 633, 344–350 (2024).
