Polarized Raman Microscopy to Image Microstructure Changes in Silicon Phthalocyanine Thin‐Films

Abstract

The choice of deposition technique and post deposition treatment can significantly influence the performance of organic electronic devices by altering the complex relationship between film properties and charge transport. Herein, the influence of deposition method and post deposition thermal annealing on the thin‐film properties of an emerging semiconductor, bis(tri‐n‐propylsilyl oxide) SiPc ((3PS)2‐SiPc), is examined by polarized Raman microscopy. Comparing physical vapor deposition (PVD) and spin‐coating, the orientation of (3PS)2‐SiPc molecules in films is determined and further characterized by X‐ray diffraction to assess variations in microstructure and morphology due to thermal annealing. Despite differences in film formation, non‐annealed organic thin‐film transistors (OTFTs) fabricated by PVD and spin‐coating resulted in similar electron mobilities (μe) on the order of 10−2 cm2 V−1 s−1 and threshold voltages (VT) of 10–20 V. Films fabricated by PVD annealed at 175 °C transition to a new polymorphic form with molecules aligned at a higher angle to the substrate and exhibiting reduced device performance. Conversely, spin‐coated films do not undergo any new polymorph formation or structural reorganization with thermal annealing. PVD fabricated films are thus more readily able to undergo transformations to structure and morphology with post deposition processing, while the microstructure of spin‐coated films is established at the time of deposition.

Oxy Phosphorus Triazatetrabenzocorrole as a p-Type Organic Semiconductor in Organic Thin Film Transistors

“…To further examine the thin films, we employed polarized Raman microscopy. We, and others, − have demonstrated that quantifying the intensity changes in Raman signals associated with the in-plane bonds of small-molecule semiconductors with different laser polarities makes it possible to extract the molecular orientation relative to the surface (Figure c). When applying this analysis across each pixel, we can provide average molecular orientation maps that demonstrate the degree of edge-on versus face-on orientation across the film.…”

Organic Thin Film Transistor-Based Cannabinoid Sensors

“…Cl-AlPc has a reactive chloro axial group, which can be easily modified through phenoxylation reactions, leading to a handle for engineering the solid-state interactions in the thin film. Our group has employed this strategy to improve silicon phthalocyanine (R 2 -SiPc)-based OTFTs ,− and ammonia sensors , with great success. Therefore, we synthesized a series of phenoxylated Cl-AlPcs (phenoxy-AlPc) and compared them with the baseline Cl-AlPc .…”