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Picture Courtesy: pib

Context:

Stabilizing perovskite nanocrystals (PNCs) and its implications for next-generation optoelectronic devices.

News in Detail

Researchers at the Centre for Nano and Soft Matter Sciences (CeNS) in Bengaluru, have developed an innovative method to stabilize CsPbX₃ perovskite nanocrystals by minimizing anion migration, a key factor behind their sensitivity to heat, moisture, and color instability.

This progress provides the way for durable, energy-efficient optoelectronic devices like perovskite LEDs (PeLEDs), addressing critical challenges in next-generation lighting technology.

Evolution of Lighting Technology

According to the International Energy Agency, electricity for lighting accounts for almost 20% of electricity consumption and 6% of CO2 emissions worldwide. Key milestones include:

1960s: Invention of LEDs.
1993: Shuji Nakamura’s high-brightness blue LEDs enabled energy-efficient white LEDs (WLEDs), earning the 2014 Nobel Prize in Physics.
Modern progress:

OLEDs (Organic LEDs): Flexible but costly and short-lived.
QLEDs (Quantum Dot LEDs): Precise color control but toxic and resource-intensive.
Micro/Mini-LEDs: High brightness but limited by production costs.

PeLEDs combine OLEDs’ flexibility and QLEDs’ precision, which set them as a superior alternative. However, their instability has been a major limitation—until now.

Problem: Instability in Perovskite LEDs

Perovskites, compounds with a crystal structure similar to calcium titanate (CaTiO₃), have emerged as a promising material for LEDs due to their high brightness, energy efficiency, and color tunability. However, their widespread adoption has been restricted by:

Sensitivity to environmental factors: Moisture and heat degrade perovskite structures.
Anion migration: Halide ions (e.g., bromide, chloride) shift between quantum dots, causing color instability and reduced lifespan.

Solution: Ar-O₂ Plasma Treatment

The CeNS team synthesized green-emitting cesium lead bromide (CsPbBr₃) nanocrystals using a hot injection method, where oleylamine acts as a passivating ligand to stabilize the crystal surface. To enhance stability, they applied argon-oxygen (Ar-O₂) plasma treatment, which:

Cross-linked surface ligands, created a hydrophobic barrier.
Immobilized ligands, slowing anion exchange and reducing migration.
Improved color stability by several orders of magnitude.

This approach effectively covers perovskites from environmental degradation, a critical step toward commercial viability.

Source:

PIB

PRACTICE QUESTION

Q. Consider the following statements regarding Light Emitting Diodes (LEDs):

LEDs are semiconductor devices that convert electrical energy directly into light energy through the process of electroluminescence.
The color of light emitted by an LED is mainly determined by the band gap energy of the semiconductor material used.
LEDs are inherently more energy-efficient than traditional incandescent bulbs because they produce significantly less heat as a byproduct.
The operational lifespan of LEDs is shorter compared to Compact Fluorescent Lamps (CFLs) due to their sensitivity to voltage fluctuations.

How many of the above statements are correct?

A) Only one

B) Only two

C) Only three

D) All four

Answer: C

Explanation:

Statement 1 is correct: LEDs use electroluminescence to convert electrical energy directly into light, bypassing thermal processes.

Statement 2 is correct: The band gap energy of the semiconductor material (e.g., GaN for blue, AlInGaP for red) determines the emitted light’s wavelength/color.

Statement 3 is correct: LEDs produce 10% heat compared to incandescent bulbs (which waste ~90% energy as heat), making them more energy-efficient.

Statement 4 is incorrect: LEDs have a lifespan of 50,000–100,000 hours, significantly longer than CFLs (8,000–15,000 hours). Voltage fluctuations can affect LEDs, but their lifespan remains superior.