Recently, A collaborative research team led by Shanghai Institute of Optics and Fine Mechanics (SIOM) of the Chinese Academy of Sciences (CAS) and Chongqing University, reported a facile and effective surface ligand engineering way to obtain ultrastable CsPbBr₃ QDs with excellent optical properties. Their work was published in Adv. Optical Mater.

All-inorganic halide perovskites nanomaterials CsPbX₃ (X = Br, Cl, or I) have been exploited as revolutionary materials in various optoelectronic applications, such as photodetectors, photovoltaics, light-emitting diodes (LEDs) and micro/nano lasers, because of their low material cost, long-range charge transport, high absorption coefficient, tunable emission wavelength with narrow bandwidth, high photoluminescence quantum yield (PLQY) and optical gain. However, scientific challenge for perspectives of lead halide perovskite materials, especially for perovskite quantum dots (QDs) is the severely intrinsic instability, including both chemical and optical degradations.

In their experiment, the researchers synthetized CsPbBr₃ QDs by a shorter capping ligand octylamine (OLA) to replace the traditional used long ligands oleylamine (OAm), and the obtained CsPbBr₃ QDs demonstrated ultrastability that no aggregation and degradation phenomenon could be observed even after being exposed in the air for 100 days, and the spin-coated QDs films could keep 96.8% of initial PL intensity even stored under ambient condition for 5 weeks.

In addition, the OLA-capped CsPbBr₃ QDs presented a better dispersibility and the PLQY could be enhanced from 62.4% to 91.3% in low polar solvents. The OLA-CsPbBr₃ QDs films represented a lower root mean square (RMS) surface average roughness of only 2.31 nm and a longer lifetime of 22.2 ns, indicating better capacity of population accumulation at excited state for ASE.

Furthermore, ASE regarded as the stimulated emission performance was studied, and the threshold of OLA-CsPbBr₃ QDs thin films was only 60.89 μJ cm^-2, which is only 24% of the OAm-QDs ASE threshold. Meanwhile, an enhanced ASE photostability was also obtained from the OLA-QDs films with continuous pump laser excitation over 9h in ambient.

This research might provide an available strategy to improve the properties of CsPbBr₃ QDs and shed light on the potential practical applications for photoelectric devices.

The work was supported by the Strategic Priority Research Program of CAS, the National Key R&D Program of China, and the Open Fund of the State Key Laboratory of High Field Laser Physics.

(a) Photographs under daylight and 365 nm UV light of CsPbBr₃ QDs with OAm/OLA in hexane. (b) PL stability measurement of CsPbBr₃ QDs films with OLA in hexane. (c) OLA-CsPbBr₃ QDs film under emission at 400 nm (290.43 μJ cm^-2).  (Image by SIOM)

Article website:
https://onlinelibrary.wiley.com/doi/10.1002/adom.202000977

Contact:
Mr. Wu Xiufeng
General Administrative Office
Shanghai Institute of Optics and Fine Mechanics, CAS
Email: xfwu@siom.ac.cn