DOI: https://doi.org/10.29363/nanoge.almips.2021.020
Publication date: 23rd September 2021
Metal halide perovskites in the form of nanocrystals (NCs) are highly efficient light emitters at visible-NIR wavelengths. In this work, the optical properties of single nanocrystals and ensembles will be discussed, as also applications in nanophotonics. At low temperatures, single nanocrystals can be good single photon emitters if blinking and spectral diffusion is conveniently reduced [1]. Moreover, if nanocrystals are forming ordered self-assembed nanocrystals, superfluorescence is observed and characterized by a N-dependent (N = number of nanocrystals in phase giving rise to superfluorescence) intensity and radiative lifetime enhancement [to be published]. Perovskite NCs can be also combined with other semiconductors, as PbS quantum dots and 2D semiconductors, to fabricate more efficient photodetectors [2,3]. In the case of disordered nanocrystal assemblies (films),stimulated emission can be observed with thresholds lower than 10 μJ/cm2 under nanosecond laser excitation at low temperatures, whose physical origin is attributed to single exciton recombination [4]. Eventually, light detecting and emitting devices based on perovskite NCs can be improved by photon recycling effect [5]. Finally, we show the effect of absorption enhancement by using Mie resonators [6] and also the important Purcell enhancement of the spontaneous emission rate in perovskite NCs using HMM structures [7]. A Purcell factor greater than three was demonstrated using CsPbI3 NCs in agreement to the calculated value in the studied HMM structure (Ag/LiF 25/35 nm thick). The thickness of the spacer allows to engineer the exciton-HMM coupling that also induces a noticeable redshift of the emitted PL. However, the HMM structures have the inconvenience of a strong reduction of the NC emission intensity, even if this negative effect can be easily overcome by using Mie scatterers, for example, and further enhancement of the radiative rate of emitters can be obtained [to be published].
Thanks are due to the spanish MICINN for financial support through the project PID2020-120484RB-I00.