Proceedings of Online Meetup: Shape-Controlled Nanocrystals: Synthesis, Characterization Methods and Applications (ShapeNC)
Publication date: 6th May 2020
The development of nanofabrication techniques enabled the experimental demonstration of different types of optical metamaterials such as Hyperbolic Metamaterials (HMMs), which are able to robustly manipulate the near field of a quantum emitter (QE) [1, 2]. Light emission of lead halide perovskites (LHPs) is currently of major interest due to their outstanding optical properties leading to highly efficient solar cells and photonic devices [3, 4]. At the level of single nanocrystals, LHPs can be also potential candidates for single photon sources [5]. For this purpose, it is important to be able to increase the photon emission rate, as commonly done by using microcavities [6]. Accordingly, in the present work we propose the manipulation of photons produced by the radiative exciton recombination in LHP nanocrystals (FAPbI3) by means of HMM structures. These HMMs have been fabricated by alternatively depositing by thermal evaporation thin metal (Ag) and dielectric (LiF) layers with 25 and 35 nm thicknesses, respectively. We have determined that the fabricated HMM exhibits a dielectric constant anisotropy of (parallel to the interfaces) and (perpendicular to the interfaces) at nm. The coupling of FAPbI3 excitons to this HMM induces a reduction up to a factor 3 of the radiative exciton lifetime by Purcell effect, when the distance between HMM and QEs is 10 nm. The Purcell factor decreases by increasing the spacer thickness, which arises from the importance of the optical coupling of FAPbI3 QEs to the modes of the HMM substrates. Furthermore, this variable distance (and coupling) is also affecting the PL peak wavelength.
Financial support from Spanish MINECO through Project No. TEC2017-86102-C2-1-R and the European Research Council (ERC) via Consolidator Grant (724424|No-LIMIT) are gratefully acknowledged. S. G. acknowledges her \Grisolia" grant from Generalitat Valenciana