Dresden 2017 – wissenschaftliches Programm
CPP 13.20: Poster
Montag, 20. März 2017, 18:30–21:00, P1A
Temperature-dependent optical spectra of (CH3NH3)PbBr3 single-crystals cleaved in ultrahigh vacuum — •Oskar Schuster1, Max Wilhelm1, Daniel Niesner1, Ievgen Levchuk2, Andres Osvet2, Shreetu Shrestha2, Miroslaw Batentschuk2, Christoph Brabec2, 3, and Thomas Fauster1 — 1Lehrstuhl für Festkörperphysik, FAU Erlangen-Nürnberg, Staudtstr. 7, D-91058 Erlangen, Germany — 2I-MEET, Department of Materials Science and Engineering, FAU Erlangen-Nürnberg, Martensstr. 7, D-91058 Erlangen, Germany — 3ZAE Bayern, Haberstr. 2a, D-91058 Erlangen, Germany
Temperature-dependent optical spectroscopy determines basic properties like band gap, exciton binding energy, and direct or indirect character of the gap. Differences have been reported between freshly cleaved crystals compared to as-grown ones or thin films. We present an approach that determines the absorption of cleaved crystals from measured one-photon and two-photon induced photoluminescence spectra. The extracted low-temperature band gap and exciton binding energy of 22 meV are in excellent agreement with the ones determined from other techniques. The direct band gap increases with temperature at <200 K, and decreases at higher temperature. The behavior is well described by the Bose-Einstein model. The associated exciton binding energy decreases for temperatures >200 K. We find a second transition 60 meV (90 meV) below the direct gap in the orthorhombic (tetragonal) phase, consistent with a slightly indirect gap. Emission from this transition is significantly reduced after exposing the crystals to air.