Hydrogen-Like Wannier-Mott Excitons in Single Crystal of Methylammonium Lead Bromide Perovskite1

Efrat Lifshitz^a, Aldona Sashchuik^a, Georgy I. Maikov^a, Jenya Tilchin^a, Maksym V. Kovalenko^b^,^c, Dmitry N. Dirin^b^,^c

^aSchulich Faculty of Chemistry, Russell Berrie Nanotechnology Institute, Solid State Institute, Technion,, Technion City, Haifa, 42000, Israel

^bETH Zürich, Department of Chemistry and Applied Biosciences, Switzerland, Switzerland

^cEMPA - Swiss Federal Laboratories for Materials Science and Technology, Überland Strasse, 129, Dübendorf, Switzerland

Materials for Sustainable Development Conference (MATSUS)
Proceedings of September Meeting 2016 (NFM16)

Berlin, Germany, 2016 September 5th - 13th

Organizers: Marin Alexe, Enrique Cánovas, Celso de Mello Donega, Ivan Infante, Thomas Kirchartz, Maksym Kovalenko, Federico Rosei, Lukas Schmidt-Mende, Laurens Siebbeles, Peter Strasser, Teodor K Todorov, Roel van de Krol and Ulrike Woggon

Poster, Jenya Tilchin, 104
Publication date: 14th June 2016

The halide perovskites have elicited substantial interest in the past due to their unusual physical properties, combining efficient optical transitions and high carrier mobility. Dormant interest has revived due to groundbreaking discoveries of the perovskites' usefulness in photovoltaic cells. Moreover, those materials also showed high performance in a few optoelectronic applications such as light emitting diodes, lasers, photodetectors and future prospect for single photon source and spin electronics.Pillars that define the photo-physical properties of the perovskites and may control practical applications are related to the questions of an exciton binding energy, dielectric screening and spin-physics. In the current study we provide thorough investigation of exciton properties in orthorhombic phase of bulk CH3NH3PbBr3 perovskite single crystals by recording the reflectance, steady-state, transient photoluminescence and magneto-photoluminescence spectra of sub-micron volumes across the crystal. The study included an examination of the spectra profiles at various temperatures and laser excitation fluencies. The results resolved the first and second hydrogen-like Wannier-Mott exciton transitions at low temperatures, out of which the ground-state exciton's binding energy of 15.33 meV and Bohr radius of ~ 4.38 nm had been derived. Furthermore, the photoluminescence temperature dependence suggested dominancy of delayed exciton emission at elevated temperatures, originated from de-trapping of carriers from shallow traps or/and from re-trapping of electron-hole pairs into exciton states. We explain the exciton dynamics between singlet and triplet states basing on the differences between the g-factor of the electron and the hole. The study revealed important knowledge about critical physical parameters about three-dimensional Wannier-Mott excitons that can be rescaled appropriately for cases in low dimensional perovskite materials (nanocrystals, platelets or thin films) often used in device applications.

[1] submitted to ACSNano.

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