Study of Small-Molecule Thin Organic Films Deposited on Porous Silicon Substrates

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Study of Small-Molecule Thin Organic
FilmsDeposited on Porous Silicon Substrates

• Zbigniew Lukasiak Andrzej Korcala, Przemyslaw
  Plóciennik, Anna Zawadzka
• Department of Technical and Applied Physics
• Faculty of Physics, Astronomy and Informatics
• Nicolaus Copernicus University - Torun

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Outline

• Introduction
• Sample preparation
• Porous silicon (PSi)
• copper phthalocyanine by PVD
• Characterisation by time resolved spectroscopy
• Results for PSi and PSi/CuPc
• Summary

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Why porous silicon is interesting?

• SciencePorous Si is silicon structure and bulk
  Si is inefficient at emitting light, even at
  cryogenic temperatures.
• EconomySimple technology and low costs.
• TechnologySilicon is the most technologically
  important material, dominating the
  microelectronics revolution that influences our
  everyday lives.

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Porous siliconSi mixture of nanostructures
A - silicon wafer (substrate) B - wires (gt500
nm) C - quantum wires (1-100 nm) D , G -
nanocrystallites (1-10 nm) E - oxide layer F -
contact layer surface to volume ratio 200 - 1000
m2/cm3
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Preparation of porous silicon
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Copper phthalocyanine (CuPc)
small-molecule organic material used as a hole
transport layer in OLED and OPV structures
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Thin films preparation by PVD(thermal
evaporation in vacuum)
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Characterisation by time resolved
photoluminescence
200 ?s - for porous silicon
5 ns
PM
transient recorder
S
L
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Time resolved spectra decay curves
INTENSITY
TIME
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Photoluminescence time-resolved spectra for
different delays
0, 5µs, 10µs, 20µs, 40µs, 60µs, 80µs, 100µs,150µs
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Photoluminescence(decomposed as a sum of few
Gaussians)
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Decay of photoluminescence
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Recombination
defect
tunnelling nonradiative (fast decay)
radiative (slow decay)
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Conclusions

• PL spectra of PSi/CuPc exhibit the same multiband
  structure like for fresh prepared PSi.
• The results shows that origin of PL is the same
  for fresh and organic coated samples.
• The organic material penetrates deep into PSi
  skeleton and influences generation and
  recombination processes of carriers in PSi
  structure.
• The results are interesting for aplication of PSi
  as a part of hybrid PSi-organic photovoltaic
  devices or selective gas detectors (electrical
  noses)

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Thank you for your attention
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Relaxation of carriers in PSi structure
Wr - radiative recombination (slow) Wnr -
nonradiative recombination (fast) Wij -
migration between different zones of
structure (very slow)
loses
delayed injection
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Model of luminescence
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Future

• NOT ONLY LEDs
• flat displays
• solar cells
• gas sensors
• humidity sensors
• electronic noses
• enviroment monitoring
• blood diagnostics
• implants - cyberbones
• explosives !