Direct Time-Resolved Spectroscopic Probes of Photon Reabsorption in Lead Halide Perovskite Microwires
Ibrahim Dursun a, Yangzi Zheng b, Yuri Gartstein b, Osman Bakr a, Omar Mohammed a, Anton Malko b
a King Abdullah University of Science and Technology (KAUST) Division of Physical Sciences and Engineering, Thuwal 23955-6900, Kingdom of Saudi Arabia, Thuwal, Saudi Arabia
b The University of Texas at Dallas, Department of Physics, Richardson, TX, 75080
nanoGe Perovskite Conferences
Proceedings of nanoGe International Conference on Perovskite Solar Cells, Photonics and Optoelectronics (NIPHO19)
International Conference on Perovskite Photonics and Optoelectronics
Jerusalem, Israel, 2019 February 24th - 27th
Organizers: Lioz Etgar and Paul Meredith
Oral, Yuri Gartstein, presentation 024
DOI: https://doi.org/10.29363/nanoge.nipho.2019.024
Publication date: 21st November 2018

Solution-processed organic−inorganic and all-inorganic lead halide perovskite semiconductors have rapidly progressed as versatile and promising materials for a number of optoelectronic applications. Facile solution processing allows for various nano- and microstructures to be fabricated out of perovskite materials of different compositions. The optimization of the performance of potential devices would critically depend on the assessment and understanding of fundamental photophysical properties and processes in perovskites and their dependence on the composition. The intrinsic quantum yield of the photon emission and the character of the emission processes: e.g., free electron-hole recombination vs. excitonic recombination, are among such fundamental properties. Related to them is the nature of the long-range spatial propagation of photoexcitations, which might occur via diffusion of charge carriers and via reabsorption of photons emitted during recombination (photon recycling).

In this work, we use time- and spectrally-resolved double-objective photoluminescence (PL) spectroscopy to directly demonstrate photon reabsorption taking place in cesium-based lead halide perovskite microwires of different compositions, including CsPbBr3 [1]. We vary the spatial separation between the excitation and collection objectives focused on a single microwire and observe the appearance of time-delayed PL emission at separations exceeding 100 microns from the excitation spot. In independent measurements, we find that the mobility of charge carriers in the studied materials is low enough for the charge carrier diffusion to be irrelevant for observed spatiotemporal evolution of PL. As the separation increases, the data shows a clear pattern of the rise times in PL dynamics thus signifying its origin in the photon reabsorption assisted by the emitted light trapping in the microwire waveguides. We also observe the PL spectrum developing red shifts increasing with the separation. The details of these signatures are found to depend on the composition of the wire material. We observe that the composition can dramatically alter the excitation power dependence of the PL: from the power dependence corresponding to free electron-hole recombination to the one corresponding to the excitonic (or geminate) recombination.

We compare experimental data to the results of a quantitative kinetic model developed to account for contributions of mono- and bimolecular recombination in the presence of waveguide-assisted emission-reabsorption events. This comparison enables us to assess the intrinsic quantum yield of elementary radiative recombination events.

 

The KAUST group gratefully acknowledges funding support from KAUST, Technology Innovation Center for Solid State Lighting at KAUST. The work of the UT Dallas group was supported by the U.S. Department of Energy, Office of Basic Energy Sciences, Division of Materials Sciences and Engineering under Award No. DE-SC0010697.

© Fundació Scito
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