Stable and Efficient White Photoluminescence from Cesium Lead Halide Perovskite Nanocrystals/Polyfluorene Organogel Composite by Suppressing of Halide Ion Migration

• Published in: Advanced optical materials Vol. 9; no. 19
• Main Authors: Muthu, Chinnadurai, Pious, Johnpaul K., Thankachan, Tino, Krishna, Nayana, Vijayakumar, Chakkooth
• Format: Journal Article
• Language: English
• Published: Weinheim Wiley Subscription Services, Inc 01.10.2021
• Subjects: Cesium; Current carriers; Emissions control; Energy gap; Energy transfer; halide ion migration; halide perovskites; Ion migration; Lead compounds; Light emission; Materials science; Metal halides; Nanocrystals; Optics; Optoelectronics; organogels; Perovskites; Photoluminescence; white‐light emission
• ISSN: 2195-1071; 2195-1071
• DOI: 10.1002/adom.202100601

Luminescent perovskite nanocrystals (PNCs) receive great attention in recent years due to their sharp, intense, and easily tunable photoluminescence, suitable for optoelectronic applications. However, in reality, the emission bandgap tunability is limited due to rapid halide ion migration, commonly occurring in mixed halide perovskites. Consequently, it is challenging to produce white‐light emission by mixing PNCs having different emission colors. In this work, using a blue‐emitting polyfluorene (PF) to passivate the surface of yellow‐emitting CsPbBr1.5I1.5 based mixed halide PNC is reported not only to suppress the halide ion migration but also to generate stable and efficient white‐light emission through controlled excitation energy transfer from the former to the latter. PF gel arrests the detachment of capping ligands from the surface of nanocrystals, thereby hinders the halide ion migration and prevents the generation of related trap states. Consequently, the nonradiative recombination of photogenerated charge carriers has significantly reduced, resulting in the overall enhancement of the luminescence characteristics of the nanocrystals. The halide ion migration in yellow‐emitting cesium lead halide perovskite nanocrystals is entirely suppressed by embedding them into a blue‐emitting polyfluorene (PF) gel matrix. Stable and efficient white‐light emission is obtained due to excitation energy transfer from PF gel to the nanocrystals.