study of small-molecule thin organic films deposited on porous silicon substrates zbigniew Łukasiak...

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

Zbigniew ŁukasiakZbigniew Łukasiak

Andrzej Korcala, Przemysław Płóciennik, Andrzej Korcala, Przemysław Płóciennik, Anna ZawadzkaAnna Zawadzka

Department of Technical and Applied PhysicsDepartment of Technical and Applied Physics

Faculty of Physics, Astronomy and InformaticsFaculty of Physics, Astronomy and Informatics

Nicolaus Copernicus University - ToruńNicolaus Copernicus University - Toruń

OutlineOutline

• Introduction• Sample preparation

– Porous silicon (PSi)– copper phthalocyanine – by PVD

• Characterisation by time resolved spectroscopy• Results for PSi and PSi/CuPc• Summary

Study of Small-Molecule Thin Organic FilmsStudy of Small-Molecule Thin Organic Films Deposited on Porous Silicon SubstratesDeposited on Porous Silicon Substrates 22


Why porous silicon is interesting?Why porous silicon is interesting?

Science:Porous Si is silicon structure and bulk Si is inefficient at emitting light, even at cryogenic temperatures.

Economy:Simple technology and low costs.

Technology:Silicon is the most technologically important material, dominating the microelectronics revolution that influences our everyday lives.


Porous siliconPorous siliconSi mixture of nanostructuresSi mixture of nanostructures

A

B

C

D

E

F G

A - silicon wafer (substrate) B - wires (>500 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


+ -

h a log en lam p

m ixer

cu rren t so u rceS i w afer

O -r in g

e lectro ly te

cell

b ack sid e con ta ct

p la tin iu m ca th od e

Preparation of Preparation of porous siliconporous silicon

Copper phthalocyanine (CuPc)Copper phthalocyanine (CuPc)


66

small-molecule organic material used as a hole transport layer in OLED and OPV structures

Thin films preparation by PVDThin films preparation by PVD(thermal evaporation in vacuum)(thermal evaporation in vacuum)



~5 ns

PM

L

S

~200 s - for porous silicon

transient recorder

Pulse LaserPulse Laser

for nitrogen laserfor nitrogen laser samplesample

Filter (monochromator)Filter (monochromator)

photomultiplierphotomultiplier

Boxcar, Boxcar, digital oscilloscope, digital oscilloscope, RTMSRTMS

Characterisation by time resolved Characterisation by time resolved photoluminescencephotoluminescence


TIME

INTENSITY

OBSERVATION WAVELENGTH

constant wavelength, changed delaydecay curves of luminescence

constant delay, changed wavelength luminescence time resolved spectra

Time resolved spectra & decay curvesTime resolved spectra & decay curves

Photoluminescence time-resolved Photoluminescence time-resolved spectra for different delaysspectra for different delays


0, 5μs, 10μs, 20μs, 40μs, 60μs, 80μs, 100μs,150μs

PhotoluminescencePhotoluminescence(d(decomposed as a sum of few Gaussiansecomposed as a sum of few Gaussians))


1111

Decay of photoluminescenceDecay of photoluminescence



RecombinationRecombination

nE0V

bd

radiative(slow decay)

defect

tunnellingnonradiative(fast decay)

Wd

hm V Enr

Bn

exp

42 0

cry sta llites on th e su r face o f q u an tu m w ires


ConclusionsConclusions

• 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”)

Thank you for your attentionThank you for your attention


1515


1616


1717


Relaxation of carriers in PSi structureRelaxation of carriers in PSi structure

j

ei

hj

hij

j

hi

ej

eij

ji,nrjii,r

h,ei

h,ei

)t(P)t(PW)t(P)t(PW

WWW)t(Pdt

)t(dP

i j

W n r

Wr

W ij

„loses”

delayed injection

Wr - radiative recombination (slow)

Wnr - nonradiative recombination(fast)

Wij - migration between different zones of structure

(very slow)


Model of Model of luminescenceluminescence

cry sta llites on th e su r face o f q u an tu m w ires


FutureFuture

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

study of small-molecule thin organic films deposited on porous silicon substrates zbigniew Łukasiak...

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