Dresden 2017 – wissenschaftliches Programm
CPP 8.3: Vortrag
Montag, 20. März 2017, 16:00–16:15, ZEU 222
Coherent Dynamics of Free Exciton Dissociation in Lead-iodide Perovskites observed by 2D Electronic Spectroscopy — •Ajay Jha1, Hong-Guang Duan1,2,3, Vandana Tiwari1, Pabitra Nayak4, Michael Thorwart2,3, Henry J. Snaith4, and R. J. Dwayne Miller1,3,5 — 1MPI-Structure & Dynamics of Matter, Hamburg, Germany — 2Universität Hamburg,Germany — 3CUI Hamburg, Germany — 4University of Oxford, UK — 5University of Toronto, Canada
Hybrid organolead halide perovskites with high carrier mobility and large dielectric constant have received considerable attention as an excellent material for low-cost efficient photovoltaics. The power conversion efficiency of perovskite based solar cells has meteorically advanced to 22.1% with excitonic dye-sensitization concept and ~15% for planar heterojunction configuration. The unprecedented success of this material demands the fundamental understanding of underlying microscopic mechanisms for photoinduced charge generation. Recent studies suggest that most photoexcitations in perovskite are free charge carriers behaving like III-V inorganic semiconductors, but the contribution of excitons has been a matter of debate. We have employed ultrafast 2D electronic spectroscopy to probe elementary optical excitation of CH3NH3PbI3 thin films. We distinctly observe the electronically coupled excitonic and free carrier transitions at room temperature. We captured an ultrafast exciton dissociation favored by low exciton binding energy of ~40 meV. The interplay of strongly coupled dominant vibrational mode to exciton dynamics will also be discussed.