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SUMMARY:Time Scales in Methylammonium Lead Iodide Perovskite Solar aAbsorb
 ers - Michael F Toney
DTSTART:20190705T133000Z
DTEND:20190705T143000Z
UID:TALK126385@talks.cam.ac.uk
CONTACT:Elizabeth Tennyson
DESCRIPTION:Hybrid organic-inorganic perovskites (HOIPs) have excited the 
 photovoltaic community due to their high light to power conversion efficie
 ncies. In this talk I will show our recent results on the lattice dynamics
  (fast time scales ≈ps) and on the HOIP formation mechanisms (slow time 
 scales ≈minutes). One of the distinguishing properties of HOIPs compared
  to conventional semiconductors is the considerable disorder in the lattic
 e that varies over length and time scales. These lattice dynamics are impo
 rtant for both the cooling and transport of photoexcited charge carriers. 
 \nIn the first part of this talk\, I describe our high-precision measureme
 nts of acoustic phonon lifetimes in the hybrid perovskite methylammonium l
 ead iodide (MAPbI3) that reveal extremely short lifetimes on the order of 
 picoseconds\, corresponding to nanometer mean free paths\, showing that ac
 oustic phonons are unable to efficiently dissipate heat. These findings il
 lustrate a fundamental difference between HOIPs and conventional photovolt
 aic semiconductors. Another surprising aspect of HOIPs is that they are sy
 nthesized under mild conditions (e.g.\, 100°C annealing) and solution pro
 cessing. I will also discuss the formation of MAPbI3 films from the single
 -step deposition of lead chloride and three equivalents of methylammonium 
 iodide (PbCl2 + 3CH3NH3I). We use X-ray scattering and absorption to d
 etermine the film formation mechanisms\, revealing the importance of a sel
 f-regulating mechanism that slows the film growth. This provides insight i
 nto optimizing processing conditions and realizing enhanced optoelectronic
  properties in HOIPs.\n
LOCATION:Kapitza Seminar Room\, Kapitza Building\, Cavendish Laboratory
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