supplementary figures...1 supplementary figures supplementary figure 1. vibrational modes of...

1

Supplementary Figures

Supplementary Figure 1. Vibrational modes of PCPDT-BT “Neutral” corresponding to

frequencies at 1567.6 cm-1

(mode labelled Na), 1477.6 cm-1

(Nb), 1395.1 cm-1

(Nc), 1252.1

cm-1

(Nd), 1169.8 cm-1

(Ne). See Figure S5(b) for the corresponding spectrum.

Na

Nb

Nc

Nd

Ne

2

C1a

C1b

C1c

C1d

C1e

C1f

3

Supplementary Figure 2. Vibrational modes of PCPDT-BT:F4-TCNQ in “Complex-1”

conformation, corresponding to frequencies at 1476.5 cm-1

(mode labelled C1a), 1388.8 cm-1

(C1b), 1194.2 cm-1

(C1c), 1033.1 cm-1

(C1d), 979.6 cm-1

(C1e), 941.8 cm-1

(C1f). The F4-

TCNQ molecule is coloured in grey and lies behind the polymer. See Figure S6(b) for the

corresponding spectrum. C1d is the mode displayed in Figure 4c of the manuscript.

4

Supplementary Figure 3. Vibrational modes of PCPDT-BT+ “Cation”, corresponding to


(mode labelled CATa), 1391.9 cm-1

(CATb), 1187.8 cm-1

(CATc),

1005.7 cm-1

(CATd), 880.3 cm-1

(CATe).

CATa

CATb

CATc

CATd

CATe

5

Supplementary Figure 4. Vibrational modes of PCPDT-BT:F4-TCNQ in “Complex-2”

conformation, corresponding to frequencies at 1567.9 cm-1


(C2b), 1393.3 cm-1

(C2c), 1232.8 cm-1

(C2d), 1169.4 cm-1

(C2e). The F4-TCNQ molecule is

coloured in grey and lies behind the polymer.

C2a

C2b

C2c

C2d

C2e

6

800 1000 12000

1

2

3

4

1400 1600

0.0

0.5

1.0

(b)

PCPDT-BT

calc.

Neutral Ne

Nd

Na

Nb

Nc

Nd

Inte

gra

ted

ab

so

rptio

n in

ten

sity

(10

8cm

mo

l-1)

Wavenumber (cm-1)

Ne

Nc

Nb

Na

No

rma

lize

d a

bso

rba

nce

exp.

0%

(a)

Supplementary Figure 5. a, Normalized FTIR absorption spectrum of a pristine PCPDT-

BT film, as shown in Figure 2a of the manuscript. Some of the experimental bands are

assigned to calculated vibrational transitions by comparing with the calculated spectrum of

PCPDT-BT in “Neutral” conformation, displayed in panel b (as in in Figure 3a of the

manuscript). The labels used for the assignment correspond to the frequencies of the modes

visualized in Figure S1.

7

800 1000 12000

20

40

60

80

1400 1600

0.0

0.5

1.0

(b)

C1f

C1e

C1d

C1cx15

PCPDT-BT

C1b

C1a

(a)

Nd

calc.

Complex-1

exp.

6.7%

Inte

gra

ted

ab

so

rptio

n in

ten

sity

(10

8cm

mo

l-1)

Wavenumber (cm-1)

C1c

C1fC1e

C1d

Ne

NcNb

Na

No

rma

lize

d a

bso

rba

nce

Supplementary Figure 6. a, Normalized FTIR absorption spectrum of a PCPDT-BT film

doped with F4-TCNQ in 6.7% molar ratio, as shown in Figure 2a of the manuscript, with no

vertical scale offset. Some of the experimental bands are assigned to calculated vibrational

transitions by comparing with the calculated spectrum of PCPDT-BT in “Complex-1”

conformation, displayed in panel b (as in in Figure 3a of the manuscript, including the 15-

fold magnification of the 1280-1600 cm-1

part of the spectrum). The bands assigned to neutral

polymer chains are also indicated, labelled as in Figure S1. The labels used for the

assignment correspond to the frequencies of the modes visualized in Figures S1-S2. Due to

dominant contribution of neutral chains to absorption in the 1350-1600 cm-1

region of the

experimental spectrum, we did not attempt to assign the C1a and C1b calculated modes.

8

Supplementary Figure 7. Vibrational modes of PCPDT “Neutral”, corresponding to


(mode labelled NHa), 1394.7 cm-1

(NHb), 1320.6 cm-1

(NHc),

1206.6 cm-1

(NHd), 1158.7 cm-1

(NHe). See Figure S10(b) for the corresponding spectrum.

NHa

NHb

NHc

NHd

NHe

9

C3f

C3a

C3b

C3c

C3d

C3e

10

Supplementary Figure 8. Vibrational modes of PCPDT:F4-TCNQ in conformation

“Complex-3”, corresponding to frequencies at 1507.7cm-1


(C3b), 1234.2 cm-1

(C3c), 1068.4 cm-1

(C3d), 1044.8 cm-1

(C3e), 990.8 cm-1

(C3f). The F4-

TCNQ molecule is coloured in grey and lies behind the polymer. See Figure S11(b) for the

corresponding spectrum.

11

CATHa

CATHb

CATHc

CATHd

CATHe

CATHf

12

Supplementary Figure 9. Vibrational modes of PCPDT+ “Cation”, corresponding to


(mode labelled CATHa), 1216.0 cm-1

(CATHb), 1011.0 cm-1

(CATHc), 920.9 cm-1

(CATHd), 892.1 cm-1

(CATHe), 870.2 cm-1

(CATHf).

13

800 1000 12000.0

0.1

0.2

0.3

0.4

0.5

1400 1600

0.0

0.5

1.0

(b)

PCPDT

calc.

Neutral

NHe

NHd

NHa

NHb

NHc

(a)

Inte

gra

ted

ab

so

rptio

n in

ten

sity

(10

8cm

mo

l-1)

Wavenumber (cm-1)

NHd/e NHc

NHb

NHa

No

rma

lize

d a

bso

rba

nce

exp.

0%

Supplementary Figure 10. a, Normalized FTIR absorption spectrum of a pristine PCPDT

film, as shown in Figure 2c of the manuscript. Some of the experimental bands are assigned

to calculated vibrational transitions by comparing with the calculated spectrum of PCPDT in

“Neutral” conformation, displayed in panel b (as in in Figure 3d of the manuscript). The

labels used for the assignment correspond to the frequencies of the modes visualized in

Figure S7. For the band peaked at 1170 cm-1

in the experimental spectrum we indicate two

possible assignments, to the calculated modes NHd and NHe.

14

800 1000 12000

20

40

60

80

1400 1600

0.0

0.5

1.0

1.5

(b)

C3f

C3e

C3d

C3c

PCPDT

calc.

Complex-3

C3b

C3a

x15

(a) NHd/e

C3a/b

C3c

C3d

C3e

C3f

Inte

gra

ted

ab

so

rptio

n in

ten

sity

(10

8cm

mo

l-1)

Wavenumber (cm-1)

NHc

NHb

NHa

No

rma

lize

d a

bso

rba

nce

exp.

6.7%

Supplementary Figure 11. a, Normalized FTIR absorption spectrum of a PCPDT film

doped with F4-TCNQ in 6.7% molar ratio, as shown in Figure 2c of the manuscript, with no

vertical scale offset. Some of the experimental bands are assigned to calculated vibrational

transitions by comparing with the calculated spectrum of PCPDT in “Complex-3”

conformation, displayed in panel b (as in in Figure 3d of the manuscript, including the 15-

fold magnification of the 1280-1600 cm-1

part of the spectrum). The bands assigned to neutral

polymer chains are also indicated, labelled as in Figure S7. The labels used for the

assignment correspond to the frequencies of the modes visualized in Figures S7-S8. For the

band peaked at 1496 cm-1

in the experimental spectrum we indicate two possible

assignments, to the calculated modes C3a and C3b.

15

Supplementary Figure 12. Optimized molecular geometries corresponding to PCPDT-

BT:F4-TCNQ in the conformations Complex-1, Complex-2 and Complex-2-PERP.

Complex-2-PERP

Complex-2

Complex-1

16

Supplementary Figure 13. Optimized molecular geometries corresponding to PCPDT:F4-

TCNQ in the conformations Complex-3 and Complex-4. The F4-TCNQ molecule lies in

front of the polymer and is coloured in grey for better visualization.

Complex-3

Complex-4

17

Supplementary Figure 14. Calculated vibrational absorption spectra of PCPDT-BT in

different conformations, without frequency scaling: single polymer strand without F4-TCNQ

(Neutral), with an F4-TCNQ molecule localized close to the CPDT moiety (Complex-1),

without F4-TCNQ molecule and one electron less on the HOMO (Cation), and with an F4-

TCNQ molecule localized close to the BT moiety (Complex-2). For Complex-1 and Cation,

a magnified part of the spectrum is also shown, with intensity multiplied 15 and 30 times

respectively.

18

0

50

100

0

20

40

60

800 1000 1200 1400 1600 18000.0

0.1

0.2

0.3

0.4

x30

In

teg

rate

d a

bso

rption

in

ten

sity (

10

8cm

mol-1

) Cation

x15

Complex-3

Neutral

Wavenumber (cm-1)

Supplementary Figure 15. Calculated vibrational absorption spectra of PCPDT in different

conformations, without frequency scaling: single polymer strand without F4-TCNQ

(Neutral), with F4-TCNQ (Complex-3), without F4-TCNQ molecule and one electron less on

the HOMO (Cation). For Complex-3 and Cation, a magnified part of the spectrum is also

shown, with intensity multiplied 15 and 30 times respectively.

19

Supplementary Tables

Supplementary Table 1. Summary of stabilization energies G and amount of charge

present on the polymer in different conformations of the complex PCPDT-BT:F4-TCNQ.

Conformation G (eV) * Charge on polymer (e) **

Complex-1 -0.46 0.93

Complex-2 -0.22 -0.02

Complex-2-PERP -0.43 -0.06 * The stabilization energy G is calculated as: G = Gcomplex – (Gpolymer + GF4-TCNQ), where Gx

are the Gibbs energies of the complex, the polymer strand and the F4-TCNQ molecule. **

According to Mulliken analysis.

Supplementary Table 2. Summary of stabilization energies G and amount of charge

present on the polymer in different conformations of the complex PCPDT:F4-TCNQ.

Conformation G (eV) *

Charge on polymer (e) **

Complex-3 -0.60 0.92

Complex-4 -0.58 0.93 * The stabilization energy G is calculated as: G = Gcomplex – (Gpolymer + GF4-TCNQ), where Gx

are the Gibbs energies of the complex, the polymer strand and the F4-TCNQ molecule. **

According to Mulliken analysis.

20

Supplementary Discussion

1. Visualization of vibrational modes and assignment to the experimental IR bands

For each of the different conformations considered in the calculations presented in Figure 3

of the manuscript, we display a selection of the computed vibrational normal modes

(Supplementary Figures 1-4 for PCPDT-BT and 7-9 for PCPDT). For each mode the

displacement vectors have been normalized in length, to visualize which parts of the

molecule move the most. We indicate the frequency of each selected mode after the

application of the same scaling factors used in Figure 3 of the manuscript. Note that we were

forced to apply a selection, due to the great amount (>100) of calculated modes having a non-

negligible IR absorption intensity in the spectral region of interest. In particular, in some

cases more than one mode is present under the same broadened peak: in these cases we have

selected for display the most intense one. We label each of the selected modes and we use the

same labels in Supplementary Figures 5 and 6, where we make a tentative assignment of the

vibrational bands observed in the experiments on pristine and 6.7% doped films of PCPDT-

BT (Figure 2 of the manuscript) by comparing with the calculated spectra (“Neutral” and

“Complex-1” respectively). The same is done in Supplementary Figures 10 and 11 for the

homo-polymer PCPDT, using the calculations on conformations “Neutral” and “Complex-3”

respectively.

2. Conformational analysis of the complexes

In addition to Complex-1, -2, -3 discussed in the manuscript, we investigated a number of

other energetically stable conformations in which the polymer:F4-TCNQ complexes can

arrange. To be as close as possible to the real system, we focused on conformations where the

F4-TCNQ molecule is in front of repeat units which are attached to alkyl side-chains. For

PCPDT-BT:F4-TCNQ we show here one optimized conformation, which we call Complex-2-

21

PERP, and compare it to Complex-1 and Complex-2 (Supplementary Figure 12). The only

conformation resulting in efficient transfer of charge is Complex-1. For PCPDT:F4-TCNQ

we show one additional optimized structure, called Complex-4, and compare it to Complex-3

(Supplementary Figure 13). In Complex-4 the F4-TCNQ molecule is in front of a different

repeat unit than in Complex-3. Furthermore, its position with respect to the repeat unit itself

is different than in Complex-3. Both conformations give efficient charge transfer. The

stabilization energies and the amount of charge transferred (from Mulliken analysis) in the

different conformations involving PCPDT-BT:F4-TCNQ and PCPDT:F4-TCNQ are

summarized in Supplementary Tables 1 and 2, respectively.

As for Complex-1, -2, -3, all the additional conformations were calculated using

CAM-B3LYP/6-31G** density functional theory, with spin-unrestricted wave functions and

including a polarizable continuum medium (r = 3) which exploits SMD (“Solvation Model

based on Density”, see Methods section of the manuscript). Cartesian coordinates of the

presented complexes are available upon request to the authors.

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