m a alam - nanohub · m_a_alam.pptx author: mark lundstrom created date: 8/10/2012 2:48:48 pm
TRANSCRIPT
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M. A. Alam, B. Ray, R. Khan, S. Dongaonkar [email protected]
Electrical and Computer Engineering Purdue University
West Lafayette, IN USA
Workshop on Theory, Modeling, and Simulation, Purdue University, West Lafayette, 2012
+4$,-5"')"*)-')",(-'&.)1"%-,).$%%)
Heterojunction, complex morphology essential for photocurrent
Planar OPV HJ splits exciton …
Bulk HJ OPV
… keeps e/h isolated
;)*"<'#):="):94$1)"*)+3>)1&?<%-5"'1)
3
First Principle (no transport) Effective Medium (no HJ)
Library of ~100s molecules exciton dissociation & hopping,
ITO Al
Blom PRB, 2005
Isaacs, J. Phy Chem Lett, 2011
J. E. Northrup, APL, 2012
Like p-i-n cells (e.g. a-Si) Heterojunctions absent
!"1:)#$6&.$)$@4$,&?$':1).-''":)A$)$@4%-&'$#)
4
Process
Device
Charac. Reliability
System
PPV P3HT P3HT PCPDTBT PTB7 ----
! PC
E (%
) FF
J. V. Li, Org. Elec., 2012
L. Zeng, APL, 2010 Renz, SOLMAT, 2011
Oosterhout, N
at. Mat, 2009
V OC (V
)
Band Gap (eV)
Scharber, Adv. Mat, 2006
Vocmax = EG - 0.3
2-4% gap
3,".$11)!"#$%2)7$?&@&'()B)/$%*C+,(-'&D-5"')
5
Polymer-A (Donor)
Solvent Polymer-B (Acceptor)
Phase Separation provies the structure necessary for BHJ-OPV
10-15 min @125-150C Cahn-Hilliard Equation
Composition, Ø
Free
Ene
rgy,
f mix
ØA ØD
Ray, Solmat, 2011.
6
7$6&.$)/&?<%-5"')B)E@4$,&?$':1)
The limits of Jsc, Voc, and FF can be easily understood
Experiment Simulation
L. Zeng, APL, 2010
3,".$11)+45?&D-5"'2)F''$-%&'()
Anneal Time (min)
Experiment
Anneal Time (min)
Effic
ienc
y (%
)
ta(opt)
Simulation
Optimum Anneal Duration WC ~Lex
WC
Late Anneal Phase (Coarse Morphology)
Early Anneal Phase (Sub- percolating Morphology)
WC >>Lex
7
Optimum anneal time predictable
[2] [1]
[3]
Experiments
Voc cannot be improved by morphology engineering
.. Voc is area independent
8
Aint/AL
V OC (V
)
VOC(BL)
Anneal Time
Generation ~ Area
Recombination ~ Area
Gyroid
Ordered
>".2)F)G-<15-')A-,(-&')
Simulation
REF: Ray, APL, 2012.
SUN
0"??<'&.-5"')(-4),$(-,#&'()>".)
Consistent with all expt. data, nothing anomalous with Voc !
Scharber, A
dv. Mat, 2006
(1.10 0.706)
(1.45, 1.111)
(1.01 0.736)
Green,
Prog. In PV, 2011
Ryyan, arXib 2012.; Atwater, Science, 2012.
V OC (V
)
Band Gap (eV)
HI$%&-A&%&:9):")A$)-##,$11$#)J)%-:$,KL) T
s =12
00C
Str
ess
Pro
cess
ing Anneal duration, ta
Ta
=120
0 C
Ts =
1000
C
Stress duration, ts
WC Anneal time (min)
J SC (
mA
/cm
2 )
ta (opt)
Low T
High T
Ta= 500
J SC (
norm
)
Stress time (h)
Ta= 800
Analytical Model
Ray, APL, 2011.
3-'$%)61M)0$%%)EN.&$'.9)J)/$%#"?)7&1.<11$#)
11 Cell/panel gap is essentially technology agnostic
P D
R
S
C
Shunt Current (ISH)
Sheet Resistance (Rsq)
Cell
Shunts distributed within module
shunt and series resistance explain the gap
Wolden, JVST, 2011
Electron
(b) F')E'#C:"CE'#)!"#$%&'()0-4-A&%&:9)E?$,(&'()
1) Process
2) Device
3) Optimization 4) Reliability
12
5) Panel
O8-:);)8-6$)%$-,'$#)*,"?)P!/)"*)+,(-'&.)0$%%1)
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Simulation tool as a repository of information Process, device, reliability,
panel performance correlated
Communication is important
Classical simulation provides many insights
Random is close to optimum A key lesson from Si electronics
Summer schools could be helpful
Should be used to complement experiments
Complex does not mean complicated