jianhua liu icsm2012
TRANSCRIPT
N
N
O
O
S
S
S
S
0 50 100 150 200 250 300
Ex
oth
erm
ic
Temperature (C)
C6PT1C6
C6PT2C6
C6PT3C6
EHPT2C6
C6PT2
Single Crystal Structure and Film X-ray Diffraction
Abstract
Intermolecular Packing and Intramolecular Conformation
Optical Absorption and Solubility
Structural variation has remarkable effects on the materials’ fundamental
properties including molecular packing, thermal transitions, crystallinity,
optical absorption, energy levels, film morphology, and hole mobility.
Single crystal structures of these DPP-based compounds were compared
in terms of molecular packing style, intermolecular overlapping (areas and
distance), and intramolecular conformation.
Differences in material properties are found to arise from changes in intra-
and intermolecular interactions in the solid state caused by the structural
variations.
This study demonstrates a systematic investigation of structure-property
relationships in conjugated small molecules.
Film Morphology and Diode Mobility
Acknowledgments: This work is supported by the NSF-CAREER/SPECIAL CREATIVITY AWARD and NSF-
SOLAR. C. K. thanks the Department of Energy, Office of Basic Research for financial support. T.-Q.N thanks the Camille Dreyfus Teacher Scholar Award and the Alfred Sloan Fellowship.
Summary
References
Liu, J.; Kim, C.; Lin, J.; Tamayo, A.; Walker, B.; Wu, G.; Nguyen, T. -Q. Chemistry of Materials 2012, 24, 1699.
Influence of Structural Variation on Solid-State Properties of
Diketopyrrolopyrrole-Based Oligophenylenethiophenes
Jianhua Liu, Chunki Kim, Jason Lin and Thuc-Quyen Nguyen
Center for Polymers and Organic Solids and Department of Chemistry & Biochemistry, University of California, Santa Barbara, California, 93106 USA
Five compounds, based on diketopyrrolopyrrole (DPP) and phenylene
thiophene (PT) moieties, are synthesized to investigate the effect of structural
variations on material’s solid state properties. The structural variations are
focused on (a) backbone length by changing the number of thiophenes on both
sides of DPP, (b) alkyl substitution (n-hexyl or ethylhexyl) on DPP, and (c) the
presence of n-hexyl group at the end of the molecular backbone.
10 20 302 °
C6PT1C6 EHPT2C6
C6PT2C6 C6PT2
C6PT3C6a
b
c
d
e
fg
h
ij
NameIntermolecular backbone
overlappinga
Interplane
distanceb (Å)
C6PT1C6 3.28
C6PT2C6 3.26
C6PT3C6 3.37
EHPT3C6 3.27c
C6PT2 3.23
Name φ1 (o) φ2 (
o)
C6PT1C6 26.2 22.8
C6PT2C6 23.7 10.2
C6PT3C6 25.1 16.5
EHPT2C6 37.6 17.4
C6PT2 26.2 14.2
N
N
O
O
R1
R1
S
S
R2
R2
φ1
φ2
a
b
c
(a) (b) (c)
(d)
(f)
(e)
300 400 500 600
0.0
0.2
0.4
0.6
0.8
1.0
Ab
so
rba
nc
e (
a.u
.)
Wavelength (nm)300 400 500 600 700
0.0
0.2
0.4
0.6
0.8
1.0 C6PT1C6
C6PT2C6
C6PT3C6
EHPT2C6
C6PT2
Ab
so
rba
nc
e (
a.u
.)
Wavelength (nm)
(a) (b)
-5.16
-3.32
C6PT2C6
-5.63
-3.66
C6PT1C6
-5.24
-3.38
C6PT3C6
-5.49
-3.51
EHPT2C6
-5.37
-3.43
C6PT2
EA
IP
Egopt
Egopt
1.97
1.84 1.86
1.981.94
-5.16
-3.32
C6PT2C6
-5.63
-3.66
C6PT1C6
-5.24
-3.38
C6PT3C6
-5.49
-3.51
EHPT2C6
-5.37
-3.52
C6PT2
LUMO
HOMO
Egopt
Egopt
1.97
1.84 1.861.98 1.85
40 80
10-6
10-5
EHPT2C6
C6PT2
C6PT1C6
C6PT2C6
C6PT3C6
Ho
le m
ob
ilit
y (
cm
2/V
s)
Temperature (C)
Name
Solution Film Tm
(ºC)
Tc
(ºC)
Solubility
(mg/mL) λmax
(nm)
λonset
(nm)
Eg (opt)
(eV)
ɛ
(M-1cm-1)
λmax
(nm)
λonset
(nm)
Eg (opt)
(eV)
HOMO
(eV)
LUMO
(eV)
C6PT1C6 505 571 2.17 3.2104 582 629 1.97 -5.63 -3.66 181 143 228
C6PT2C6 521 591 2.09 4.6104 614 674 1.84 -5.16 -3.32 231 194 11
C6PT3C6 528 602 2.06 5.6104 608 667 1.86 -5.24 -3.38 263 229 1.5
EHPT2C6 514 584 2.12 4.8104 532 626 1.98 -5.49 -3.51 164 77 53
C6PT2 516 587 2.11 4.4104 554 671 1.85 -5.37 -3.52 249 184 6.3
C6PT1C6, C6PT2C6, C6PT3C6, and C6PT2
(a-c) Vs. EHPT2C6 (d-f). Unit cells viewed
from side (a, d), a axis (b), c axis (c, f), and b
axis (e).
Experimental measured patterns
(a, c, e, g, and i) Vs. Theoretical
patterns (b, d, f, h, and j)
aViewed orthogonal to the molecular long axis with red
rectangles highlighting the overlapping area. bThe interplanar
distance is calculated from phenyl-phenyl rings. cCalculated
from overlapped DPP rings.
Intermolecular Overlapping Area and Distance
DSC thermograms (10 oC/min)
Summary of Optical and Thermal Properties
Solution state
Ionization potential (IP) and electron
affinity (EA)
AFM height images of as-cast (top)
and annealed (bottom) films.
Annealing condition: 100 ºC for 10
min. Scan size: 2 µm 2 µm.
Hole mobility of as-cast (25 ºC)
and thermal annealing (80 ºC
and 100 ºC) films.
Name φ1 (o) φ2 (
o)
C6PT1C6 26.2 22.8
C6PT2C6 23.7 10.2
C6PT3C6 25.1 16.5
EHPT2C6 37.6 17.4
C6PT2 26.2 14.2
N
N
O
O
R1
R1
S
S
R2
R2
φ1
φ2
Conjugated Backbone Conformation
aφ1 (C-C-C-C) and φ2 (X-C-C-C) as
illustrated by the general molecular
structure at bottom.
C6PT1C6 C6PT2C6 C6PT3C6 EHPT2C6 C6PT2
IP determined by UPS and EA obtained by EA = Egopt - |IP|.
Thermal Property and Energy Level
Thin film XRD Two molecular packing motif observed
Absorption redshift saturates as increasing conjugate length.
Tm and solubility have opposite sequence.
Ethylhexyl substitution significantly affects solid state absorption.
Film state
N
N
O
O
SS
N
N
O
O
SSS
S
S
S
C6PT1C6 EHPT2C6
C6PT2C6
C6PT3C6 C6PT3C6
N
N
O
O
SSS
S
Conjugation length
Alkyl chain on DPP
End alkyl chain Conjugation length
N
N
O
O
S
S
S
S