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SUMMARY:Highly Luminescent Nanocrystals of Caesium and Formamidinium Lead 
 Halide Perovskites: From Discovery to Applications - Prof Dr Maksym Kovale
 nko
DTSTART:20190312T143000Z
DTEND:20190312T153000Z
UID:TALK120760@talks.cam.ac.uk
CONTACT:Emrys Evans
DESCRIPTION:We discuss the discovery and recent developments of colloidal 
 lead halide perovskite nanocrystals (LHP NCs\, NCs\, A=Cs+\, FA+\, FA=form
 amidinium\; X=Cl\, Br\, I) [1\,2\,3]. We survey the synthesis methods\, op
 tical properties and prospects of these NCs for optoelectronic application
 s [4\,5]. \n  LHP NCs exhibit spectrally narrow (100 meV\, 12-45 nm from 
 blue-to-near-infrared) sponaneous and stimulated emission\, originating fo
 rm bright triplet excitons [6]\, and tunable over the entire visible spect
 ral region of 400-800 nm [1-4]. Post-synthestic chemical transformations o
 f colloidal NCs\, such as ion-exchange reactions\, provide an avenue to co
 mpositional fine tuning or to otherwise inaccessible materials and morphol
 ogies [7]. Cs- and FA-based perovskite NCs are highly promising for backli
 ghting of LCD displays\, for light-emitting diodes and as precursors/inks 
 for perovskite solar cells. In particular\, high purity colloids are ideal
  for further engineering as needed for photochemical/photocatalytic applic
 ations. Towards these applications\, a unique feature is that perovskite N
 Cs appear to be trap-free without any electronic surface passivaiton [8]\,
  making photogenerated electrons and holes readily availably for surface c
 hemical reactions.\n  The processing and optoelectronic applications of pe
 rovskite NCs are\, however\, hampered by the loss of colloidal stability a
 nd structural integrity due to the facile desorption of surface capping mo
 lecules during isolation and purification. To address this issue\, we have
  developed a new ligand capping strategy utilizing common and inexpensive 
 long-chain zwitterionic molecules\, resulting in much improved chemical du
 rability [9]. \n   Perovskite NCs also readily form long-range ordered ass
 semblies known as superlattices. These assemblies exhibit accelerated cohe
 rent emission (superfluorescence) [10]\, not observed before in semiconduc
 tor nanocrystal superlattices.\n\nReferences:\n\n1.	L. Protesescu et al. N
 ano Letters 2015\, 15\, 3692–3696\n2.	L. Protesescu et al. J. Am. Chem. 
 Soc.\, 2016\, 138\, 14202–14205\n3.	L. Protesescu et al. ACS Nano 2017\,
  11\, 3119–3134\n4.	M. V. Kovalenko et al. Science 2017\, 358\, 745-750\
 n5.	Q.A. Akkerman et al. Nature Materials\, 2018\, 17\, 394–405\n6.	M. A
 . Becker et al\, Nature\, 2018\, 553\, 189-193\n7.	G. Nedelcu et al. Nano 
 Letters 2015\, 15\, 5635–5640\n8.	M. I. Bodnarchuk et al. ACS Energy Let
 t.\, 2018\, in press\n9.	F. Krieg et al. ACS Energy Letter.\, 2018\, 3\, 6
 41–646\n10.	G. Raino et al. Nature 2018\, DOI: 10.1038/s41586-018-0683-0
 \n
LOCATION:Rayleigh Seminar Room\, Maxwell Centre\, Cavendish Laboratory
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