!"#$%&'()"*)+,(-'&.)/"%-,)0$%%12)

3$,14$.56$)"*)-)7$6&.$)3891&.&1:)

M. A. Alam, B. Ray, R. Khan, S. Dongaonkar alam@purdue.edu

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)

!"#

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