New Delhi, Feb 21 (AHN) Researchers at the Centre for Nano and Soft Matter Sciences (CeNS) in Bengaluru, an autonomous institute under the Department of Science and Technology (DST), have developed an innovative method to minimise anion migration in CsPbX₃ perovskite nanocrystals.

Minimising anion migration in perovskite nanocrystals can help "reduce their sensitivity to heat and moisture, as well as colour instability, paving the way for efficient, durable optoelectronic devices", said the researchers, in the paper published in the journal Nanoscale.

Lighting consumes nearly 20 per cent of global electricity, and advancements in lighting technology have significantly improved energy efficiency. From the incandescent and fluorescent lamps of the past to the invention of LEDs in the 1960s, lighting has come a long way.

However, the development of high-brightness blue LEDs in 1993, enabling energy-efficient white LEDs (WLEDs), by Shuji Nakamura and his team members marked a pivotal breakthrough. The feat was also recognised with the 2014 Nobel Prize in Physics.

Currently, LEDs lead the market in efficiency and lifespan with OLEDs that offer vibrant colours, and QLEDs (Quantum Dot LEDs) that provide precise colour control and durability. The micro/mini-LEDs that deliver high brightness and stability are also shaping the future of lighting.

While thin and flexible OLEDs (Organic LEDs) are costly and have shorter lifespans, QLEDs (Quantum Dot LEDs) are toxic and their production is challenged by resource scarcity, and Micro/Mini-LEDs are limited in their application due to high production costs.

“Perovskite (class of compounds which have the same type of crystal structure as CaTiO3 – Calcium Titanate) LEDs (PeLEDs) combine the advantages of OLEDs and QLEDs, positioning them as an excellent choice for next-generation lighting,” said the team, led by Dr. Pralay K. Santra from CeNS.

“However, their widespread application is limited by challenges such as sensitivity to heat and moisture, as well as colour instability caused by anion migration (which occurs when halide ions -- chloride, bromide, or iodide move between quantum dots in mixed layers),” they added.

To tackle this issue, Santra synthesised green light emitting cesium lead bromide (CsPbBr₃) perovskite nanocrystals using a hot injection method, where oleylamine serves as the passivating ligand.

To enhance stability, they applied argon-oxygen (Ar-O₂) plasma treatment, which immobilises the surface ligands by creating a cross-linked, hydrophobic layer.

This approach effectively stabilises the ligands and slows anion exchange -- significantly improving colour stability by several orders. The findings provide valuable insights into stabilising perovskite nanocrystals -- paving the way for efficient, durable optoelectronic devices.