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SUMMARY:Visualizing and controlling optoelectronic processes in lead halid
 e perovskites
DTSTART:20161020T163000
DTEND:20161020T173000
DTSTAMP:20260407T103049Z
UID:29591cc7983f65ffc37dc4c51c806cca3a9e135fa619cb6ef1410025
CATEGORIES:Conferences - Seminars
DESCRIPTION:Dr. Alexander Weber-Bargioni\nLawrence Berkeley National Labor
 atory\nVisualizing and understanding electronic and opto-electronic proces
 ses at their native length scale will enable unprecedented control over ma
 terial functionality. This insight is specifically critical to identify th
 e precise photo physical processes and loss mechanisms in light harvesting
  materials or to identify novel properties and functionality in quantum co
 nfined materials.\n\nIn the first part of my seminar I will report what we
  found when visualizing local opto-electronic processes critical for power
  conversion efficiency in lead halide perovskites. Photovoltaic devices ba
 sed on hybrid perovskite materials have exceeded 22% efficiency within onl
 y a few years of research and are assumed to operate homogeneous throughou
 t the material. We visualized the photo-current and photo voltage generati
 on with 10 nm spatial resolution using photo current microscopy and near f
 ield optics and find surprisingly an enormous inter and intra-grain hetero
 geneity\, which provides insight on how to optimize perovskite PV material
 s towards the theoretical limit.\n\nIn the second part of my seminar I wil
 l show how insight into the local opto-electronic processes enabled us to 
 make alternative opto electronic devices and explore novel optoelectronic 
 functionalities: We used micron sized single crystal perovskites acting as
  both cavity and gain medium\, to make these single crystals lase in quasi
  continuous wave mode or electrically contact them to create LEDs with hig
 h external quantum efficiency. In collaboration with Prof. Buonsanti’s g
 roup we reduced the size of the perovskite crystals to the quantum-confine
 d regime and assembled them in 2-D\, and found record exciton diffusion le
 ngth of over 2 um\, mediated by Foerster Resonant Energy Transfer.\n
LOCATION:CH G1 495 https://plan.epfl.ch/?room==CH%20G1%20495
STATUS:CONFIRMED
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