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SUMMARY:Discretisation Effects in the Photoluminescence of Nanostructured 
 Semiconductors - Professor Ivan Scheblykin - Lund University
DTSTART:20260331T133000Z
DTEND:20260331T143000Z
UID:TALK246196@talks.cam.ac.uk
CONTACT:136951
DESCRIPTION:When discussing semiconductor properties\, we typically focus 
 on carrier and defect concentrations\, assuming these are sufficient to ex
 plain and predict electronic properties. In this talk\, I present mapping 
 of the photoluminescence quantum yield (PLQY) over repetition rate and pul
 se fluence (so-called “horse plots”)\,[1] together with multi-pulse ti
 me-resolved photoluminescence\,[2] as experimental tools that\, in princip
 le\, enable the extraction of physically meaningful models of charge-carri
 er dynamics in metal-halide perovskite semiconductors. However\, their dir
 ect interpretation usually neglects the polycrystalline and nanostructured
  nature of perovskite films.\n\nI argue that treating halide perovskite ma
 terials as homogeneous in space and time (the standard assumption in semic
 onductor theory) is frequently inadequate. At the nanoscale\, charge dynam
 ics can be governed by only a few carriers and defect states per grain\, l
 eading to “digitised” regimes requiring stochastic descriptions.[3] Th
 is manifests\, for example\, as photoluminescence blinking caused by indiv
 idual metastable non-radiative centres.[4] Moreover\, the grainy nature of
  the material\, combined with the discrete nature of photon absorption\, r
 esults in photoluminescence dynamics that differ markedly from bulk expect
 ations\, even at identical average defect concentrations. One important co
 nsequence of these effects is an increase in PLQY with decreasing crystal 
 size below a certain threshold. This size dependence is unrelated to quant
 um confinement and instead originates from the discrete nature of light an
 d defects. Thus\, crystal size well beyond the quantum confinement regime 
 plays a important role in determining PLQY\, highlighting the importance o
 f spatial structure on length scales of approximately 50–200 nm in lumin
 escent materials and likely in solar cells.\n\n \n\n[1]        A. Kiligari
 dis\, P.A. Frantsuzov\, A. Yangui\, S. Seth\, J. Li\, Q. An\, Y. Vaynzof\,
  I.G. Scheblykin\, Are Shockley-Read-Hall and ABC models valid for lead ha
 lide perovskites?\, Nat. Commun. 12 (2021) 3329. https://doi.org/10.1038/s
 41467-021-23275-w.\n\n[2]        A. Marunchenko\, J. Kumar\, D. Tatarinov\
 , A.P. Pushkarev\, Y. Vaynzof\, I.G. Scheblykin\, Hidden Photoexcitations 
 Probed by Multipulse Photoluminescence\, ACS Energy Lett. 9 (2024) 5898–
 5906. https://doi.org/10.1021/acsenergylett.4c02404.\n\n[3]        I.G. Sc
 heblykin\, Small Number of Defects per Nanostructure Leads to “Digital
 ” Quenching of Photoluminescence: The Case of Metal Halide Perovskites\,
  Adv. Energy Mater. 10 (2020) 2001724. https://doi.org/10.1002/aenm.202001
 724.\n\n[4]        A. Merdasa\, Y. Tian\, R. Camacho\, A. Dobrovolsky\, E.
  Debroye\, E.L. Unger\, J. Hofkens\, V. Sundström\, I.G. Scheblykin\, “
 Supertrap” at Work: Extremely Efficient Nonradiative Recombination Chann
 els in MAPbI 3 Perovskites Revealed by Luminescence Super-Resolution Imagi
 ng and Spectroscopy\, ACS Nano 11 (2017) 5391–5404. https://doi.org/10.1
 021/acsnano.6b07407.
LOCATION:Lecture Theatre 2\, Department of Chemical Engineering and Biotec
 hnology\, West Cambridge Site
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