Ultra-stable perovskite nanocrystals for light-emitting applications

nimai mishra

Cesium lead halide perovskite nanocrystals (PNCs) belong to the flourishing research area in the field of photovoltaic and optoelectronic applications because of their excellent optical and electronic properties. Mainly, Cesium lead bromide (CsPbBr3) NCs with bright green photoluminescence (PL) and narrow full-width at half-maximum (FWHM) of <25 nm are the most desirable for television displays and green-emitting LEDs. However, challenges with respect to CsPbBr3 PNCs‘ stability, limit their usage in practical applications. The recent findings of Dr Nimai Mishra and his research team assert that surface passivation with an additional ligand could be an excellent, easy, and facile approach to enhancing the photoluminescence and stability of PNCs.

Dr Nimai Mishra, Assistant Professor, Department of Chemistry, along with his research group comprising of students pursuing PhD under him, Dr V G Vasavi Dutt, Mr Syed Akhil, Mr Rahul Singh, and Mr Manoj Palabathuni have published their research article titled “Year-Long Stability and Near-Unity Photoluminescence Quantum Yield of CsPbBr3 Perovskite Nanocrystals by Benzoic Acid Post-treatment“ in The Journal of Physical Chemistry C (A Q1 journal published by ‘The American Chemical Society’) having an impact factor of ~4.2.

In this article, the research group addresses the stability issues of green-emitting CsPbBr3 PNCs with simple post-treatment using benzoic acid (BA). A remarkable improvement in PLQY from 69.8% to 97% (near unity) was observed in benzoic acid-treated CsPbBr3 PNCs. The effective surface passivation by benzoic acid is also apparent from PL decay profiles of BA-CsPbBr3 PNCs. The long-term ambient stability and stability against ethanol of BA-CsPbBr3 PNCs are also well presented in the research. The PL intensity of untreated CsPbBr3 PNCs is completely lost within five months since the synthesis date, while ̴ 65% of initial PL intensity is preserved for BA-CsPbBr3 PNCs even after one year.

Furthermore, BA-CsPbBr3 PNCs exhibits excellent photo-stability where 36% of PL is retained while PL is completely quenched when the PNCs are exposed to 24 hours of continuous UV irradiation. Importantly, BA-CsPbBr3 PNCs show excellent stability against ethanol treatment as well. Finally, green, emitting diodes using BA-CsPbBr3 PNCs are fabricated by drop-casting NCs onto blue-emitting LED lights. Thus a simple benzoic acid posttreatment further presents the scope of use of these materials display technologies.

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