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SUMMARY:Defect Physics and (In)Stability in Metal-halide Perovskite Semico
 nductors
DTSTART:20181004T160000
DTEND:20181004T170000
DTSTAMP:20260406T103717Z
UID:0b91f994a72ccfda275333d68f543bc6a288310da4dc7501f8705c83
CATEGORIES:Conferences - Seminars
DESCRIPTION:Dr. Annamaria Petrozza\nCenter for Nano Science and Technology
  @Polimi\, Istituto Italiano di Tecnologia\,\nMilan\, Italy\nChE-605 - Hig
 hlights in Energy Research seminar series\nSemiconducting metal-halide per
 ovskites present various types of chemical interactions which give them a 
 characteristic fluctuating structure sensitive to the operating conditions
  of the device\, to which they adjust. This makes the control of structure
 -properties relationship\, especially at interfaces where the device reali
 zes its function\, the crucial step in order to control devices operation.
  In particular\, given their simple processability at relatively low tempe
 rature\, one can expect an intrinsic level of structural/chemical disorder
  of the semiconductor which results in the formation of defects.\nHere\, f
 irst I will present our results on the role of structural and point defect
 s in determining the nature and dynamic of photo-carriers in metal-halide 
 perovskites. Then\, I will discuss our understanding of key parameters whi
 ch must be taken into consideration in order to evaluate the suscettibilit
 y of the perovkite crystals (2D and 3D) to the formation of defects\, allo
 wing one to proceed through a predictive synthetic procedure. Finally\, I 
 will show the correlation between the presence/formation of defects and th
 e observed semiconductor instabilities. Instabilities are manifested as li
 ght-induced ion migration and segregation\, eventually leading to material
  degradation under prolonged exposure to light. Understanding\, controllin
 g and eventually blocking such material instabilities are fundamental step
 s towards large scale exploitation of perovskite in optoelectronic devices
 . By combining photoluminescence measurements under controlled conditions 
 with ab initio simulations we identify photo-instabilities related to comp
 eting light-induced formation and annihilation of trap states\, disclosing
  their characteristic length and time scales and the factors responsible f
 or both processes. We show that short range/short time defect annihilation
  can prevail over defect formation\, happening on longer scales\, when eff
 ectively blocking undercoordinated surface sites\, which act as a defect r
 eservoir. By an effective surface passivation strategy we are thus able to
  stabilize the perovskite layer towards such photo-induced instabilities\,
  leading to improved optoelectronic material quality and enhanced photo-st
 ability in a working solar cell. The proposed strategy represents a simple
  solution towards longer stability perovskite thin films that could be eas
 ily implemented in large scale manufacturing.\n\nThe seminar can also be f
 ollowed remotely by joining the online Cisco WebEx meeting (connection pos
 sible 15 minutes before the talk).\nSee here the documentation how to inst
 all the Cisco WebEx add-on on your computer.\nIn case of problem\, you can
  contact our IT support (37679 - it.vs@epfl.ch )\n 
LOCATION:I17 4 K2 https://plan.epfl.ch/?room==I17%204%20K2
STATUS:CONFIRMED
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