# Microstructural and Thermal Transport Properties of Regioregular Poly(3-hexylthiophene-2,5-diyl) Thin Films

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## Abstract

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## 1. Introduction

## 2. Materials and Methods

## 3. Results

## 4. Discussion

## 5. Conclusions

## Supplementary Materials

## Author Contributions

## Funding

## Institutional Review Board Statement

## Informed Consent Statement

## Data Availability Statement

## Acknowledgments

## Conflicts of Interest

## References

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**Figure 1.**(

**a**) Exemplary confocal microscopy image of ${\overline{M}}_{w}$ = 32.5 kg mol${}^{-1}$ spin-coated from chlorobenzene. The height is color-coded, visualizing the quartz substrate as blue and the thin film as green. (

**b**) Exemplary cumulative frequency distribution f as a function of thickness, as well as the average thickness $\overline{d}$ and the surface roughness ${S}_{q}$ calculated from subfigure (

**a**). (

**c**) Resulting film thicknesses, errors are derived from the inhomogeneities at different measurement points. Circular symbols represent films spin-coated from chlorobenzene, squares films from 1,2-dichlorobenzene, and triangles films from 1,2,4-trichlorobenzene.

**Figure 2.**Performed UV-vis absorption spectra data analysis: (

**a**) Exemplary fit on the absorption spectrum of ${\overline{M}}_{w}$ = 32.5 kg mol${}^{-1}$ spin-coated from chlorobenzene. The individual vibrational transitions sum up to the aggregate fit. (

**b**–

**e**) Extracted fraction of aggregates, 0–0 transition energy, exciton binding energy and Gaussian linewidth.

**Figure 3.**Performed GIWAXS analysis: (

**a**) 2D GIWAXS data of ${\overline{M}}_{w}$ = 92.5 kg mol${}^{-1}$ spin-coated from 1,2,4-trichlorobenzene. (

**b**) Horizontal cut of the 2D data showing the individual fitting contributions. (

**c**) Normalized peak amplitude of the horizontal $\pi $-$\pi $ stacking signal (001). (

**d**) Normalized peak amplitude of the vertical lamellar stacking signal (100). The shown data sets are carried out on samples with a comparable thickness. The obtained peak amplitudes are normalized with the amount of examined material from individual absorption measurements.

**Figure 4.**Performed photoacoustic data analysis: (

**a**) Exemplary fit on the measured phase shift of ${\overline{M}}_{w}$ = 32.5 kg mol${}^{-1}$ spin-coated from chlorobenzene. (

**b**) Extracted thermal conductivities for the different molecular weights and solvents. Circular symbols represent films spin-coated from chlorobenzene, squares films from 1,2-dichlorobenzene, and triangles films from 1,2,4-trichlorobenzene.

**Figure 5.**Correlations between extracted microstructural properties and thermal conductivity: (

**a**) Relation between the fraction of aggregates and the thermal conductivity. (

**b**) Relation between the exciton binding energy and the thermal conductivity. Color code: violet: low ${\overline{M}}_{w}$ samples, red: medium ${\overline{M}}_{w}$ samples, yellow: high ${\overline{M}}_{w}$ samples. Circular symbols represent films spin-coated from chlorobenzene, squares films from 1,2-dichlorobenzene, and triangles films from 1,2,4-trichlorobenzene.

**Table 1.**Utilized spin-coating parameters (concentration c and rotation speed $\omega $) for all combinations of molecular weights and solvents.

Solvent | ${\overline{\mathit{M}}}_{\mathit{w}}$ = 32.5 kg mol${}^{-1}$ | ${\overline{\mathit{M}}}_{\mathit{w}}$ = 62.5 kg mol${}^{-1}$ | ${\overline{\mathit{M}}}_{\mathit{w}}$ = 92.5 kg mol${}^{-1}$ |
---|---|---|---|

Chlorobenzene | $c=50$ mg mL${}^{-1}$, $\omega =750$ rpm | $c=50$ mg mL${}^{-1}$, $\omega =750$ rpm | $c=30$ mg mL${}^{-1}$, $\omega =500$ rpm |

1,2-Dichlorobenzene | $c=55$ mg mL${}^{-1}$, $\omega =500$ rpm | $c=55$ mg mL${}^{-1}$, $\omega =500$ rpm | $c=55$ mg mL${}^{-1}$, $\omega =1000$ rpm |

1,2,4-Trichlorobenzene | $c=70$ mg mL${}^{-1}$, $\omega =500$ rpm | $c=70$ mg mL${}^{-1}$, $\omega =500$ rpm | $c=70$ mg mL${}^{-1}$, $\omega =1000$ rpm |

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**MDPI and ACS Style**

Herrmann, K.; Freund, S.; Eller, F.; Rößler, T.; Papastavrou, G.; Herzig, E.M.; Retsch, M.
Microstructural and Thermal Transport Properties of Regioregular Poly(3-hexylthiophene-2,5-diyl) Thin Films. *Materials* **2022**, *15*, 7700.
https://doi.org/10.3390/ma15217700

**AMA Style**

Herrmann K, Freund S, Eller F, Rößler T, Papastavrou G, Herzig EM, Retsch M.
Microstructural and Thermal Transport Properties of Regioregular Poly(3-hexylthiophene-2,5-diyl) Thin Films. *Materials*. 2022; 15(21):7700.
https://doi.org/10.3390/ma15217700

**Chicago/Turabian Style**

Herrmann, Kai, Simon Freund, Fabian Eller, Tamino Rößler, Georg Papastavrou, Eva M. Herzig, and Markus Retsch.
2022. "Microstructural and Thermal Transport Properties of Regioregular Poly(3-hexylthiophene-2,5-diyl) Thin Films" *Materials* 15, no. 21: 7700.
https://doi.org/10.3390/ma15217700