Photon Recycling in CsPbBr3 Perovskite Nanocrystal Integrated in Polymer Waveguides
Juan Navarro Arenas a, Isaac Suárez a b, Vladimir Chyrvony a, Andrés F. Gualdrón Reyes c, Iván Mora Seró c, Juan P. Martínez Pastor a
a Instituto de Ciencia de Materiales (ICMUV), Universidad de Valencia, C/ Catedrático José Beltrán, 2, E-46980 Paterna, Spain.
b Escuela Técnica Superior de Ingenieros de Telecomunicación, Universidad Rey Juan Carlos, 28943 (Madrid)
c Universitat Jaume I, Institute of Advanced Materials (INAM) - Spain, Avinguda de Vicent Sos Baynat, Castelló de la Plana, Spain
nanoGe Perovskite Conferences
Proceedings of International Conference on Perovskite Thin Film Photovoltaics and Perovskite Photonics and Optoelectronics (NIPHO20)
Sevilla, Spain, 2020 February 23rd - 25th
Organizer: Hernán Míguez
Poster, Juan Navarro Arenas, 060
Publication date: 25th November 2019

Perovskite nanocrystals (PNCs) have recently emerged as a new class of nanomaterials with extraordinary light absorption/emission properties, and with even more perspectives than traditional colloidal quantum dots [1]. Films of PNCs are being used for the development of optoelectronic devices, given their high absorption coefficient and emission efficiency. In this context, it is well known that the huge overlap between the absorption and the photoluminescence (PL) spectra in organometallic perovskite materials, especially NCs, favors the so-called photon recycling (PR) effect [2,3]. PR consists of multiple reabsorption and reemission events in different nanocrystals of the film, which would produce an increase of the PL decay time and the final enhancement of the solar cell efficiency. Since an optical waveguide is a promising geometry to extend the PR over long distances, we propose a planar waveguide configuration to optimize the reabsorption/reemission processes, and with it the PR effect. In particular, very thin layers (50-300 nm) of close packed CsPbBr3 PNCs are deposited between two poly(methyl methacrylate) (PMMA) slabs. We have already demonstrated that this structure efficiently enhances light absorption and emission due to the high confinement of the electromagnetic field within the active layer [4]. The PR effect is producing a Stokes-shift of the collected PL up to 10 nm. Moreover, the PL decay time at the exit edge of the waveguide, as measured by frequency-domain fluorescence spectroscopy, exhibits a clear correlation with the Stokes shift, i.e., with the diffusion path for the propagating photons (which is a parameter in our experiments). Stochastic Monte Carlo simulations reproduce quite well the experimental results and predict the time delay between the injection of primary photons at the entrance edge of the waveguide and the secondary photons produced by PR at the waveguide exit edge. These results bring new knowledge to the photon dynamics inside waveguides that would be of interest for improving the efficiency of optoelectronic (solar cells, LEDs) and photonic (lasers) devices.

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