Scanning Angle Raman Spectroscopy of Poly(3-hexylthiophene)-Based Films on Indium Tin Oxide, Gold, and Sapphire Surfaces

Abstract

Interest in realizing conjugated polymer-based films with controlled morphology for efficient electronic devices, including photovoltaics, requires a parallel effort to characterize these films. Scanning angle (SA) Raman spectroscopy is applied to measure poly(3-hexylthiophene) (P3HT):phenyl-C61-butyric acid methyl ester (PCBM)-blend morphology on sapphire, gold, and indium tin oxide interfaces, including functional organic photovoltaic devices. Nonresonant SA Raman spectra are collected in seconds with signal-to-noise ratios that exceed 80, which is possible due to the reproducible SA signal enhancement. Raman spectra are collected as the incident angle of the 785 nm excitation laser is precisely varied upon a prism/sample interface from approximately 35 to 70°. The width of the ∼1447 cm(-1) thiophene C═C stretch is sensitive to P3HT order, and polymer order varied depending on the underlying substrate. This demonstrates the importance of performing the spectroscopic measurements on substrates and configurations used in the functioning devices, which is not a common practice. The experimental measurements are modeled with calculations of the interfacial mean square electric field to determine the distance dependence of the SA Raman signal. SA Raman spectroscopy is a versatile method applicable whenever the chemical composition, structure, and thickness of interfacial polymer layers need to be simultaneously measured.

Extracting interface locations in multilayer polymer waveguide films using scanning angle Raman spectroscopy

“…Similar trends are observed for sample 3‐Bi (Figure S2A) and sample 3‐Tri (Figure S3A). These representative calculated results suggest that it should be feasible to use SA Raman spectroscopy, with a signal that is proportional to the electric field intensity, to measure total film thickness as well as the location of polymer interfaces for both bilayer and trilayer films.…”

“…Scanning angle (SA) Raman spectroscopy is a technique that couples a sample to a prism (a schematic is shown in the top of Figure ), and a data set consists of the Raman spectra as a function of the incident angle of the excitation light. SA Raman spectroscopy has been used to measure polymer waveguide thicknesses, buried bilayer film interfaces, and mixed polymer film chemical composition . Other reported methods that are similar to SA Raman spectroscopy, variable‐angle internal reflection, and ATR Raman spectroscopy have been used to measure bilayer polymer films .…”

Quantitative Comparison of Organic Photovoltaic Bulk Heterojunction Photostability Under Laser Illumination

“…Other sample preparation and thicknesses are shown in Table 1 The Journal of Physical Chemistry C section compared to the polymers. 26 Using the same collection parameters, ∼10× more signal is measured for P3HT compared to PCDTBT and PTB7. The latter two have similar signal intensities.…”

Combined measurement of directional Raman scattering and surface-plasmon-polariton cone from adsorbates on smooth planar gold surfaces

“…Furthermore, the multidimensionality of the data (cone diameter and intensity and Raman scattering as a function of incident angle) provides the ability to measure more sample properties compared to either SPR or Raman scattering techniques alone. This is highlighted by our related previous work using a technique called scanning angle Raman spectroscopy, [37][38][39][40][41][42][43][44][45] whereby the incident light is scanned over a wide range of angles while simultaneously collecting the reflected light from the prism side and Raman scattering on the sample side of the interface. Scanning angle Raman spectroscopy (in the absence of a gold film) was used to identify buried interfaces in a multi-layered system with ~10s of nanometer spatial resolution.…”