Supramolecular Architecture and Electrical Properties of a Perylene Derivative in Physical Vapor Deposited Films

Abstract

The supramolecular structure of organic thin films is a key factor in their optical and electrical properties and, consequently, in the technological applications involving organic electronic. Here, thin films of a perylene derivative, the bis butylimido perylene (BuPTCD), were produced by vacuum thermal evaporation (PVD, physical vapor deposition). The main objective is to investigate the supramolecular structure of the BuPTCD in these PVD films, which implies to control their thickness at nanometer scale and to determine their molecular organization, morphology at micro and nanometer scales and crystallinity. The ultraviolet-visible absorption reveals a uniform growth of the PVD films. The optical and atomic force microscopy images show a homogeneous surface of the film at micro and nanometer scales, respectively. The X-ray diffraction indicates that both powder and PVD film are in the crystalline form. Complementary, a preferential head-on orientation of the molecules in the PVD films is determined via infrared absorption spectroscopy. Besides, the annealing process (200 o C) did not affect the molecular organization of the PVD films, revealing a thermal stability of the BuPTCD molecules within the PVD films. Through DC electrical measurements, an electrical conductivity of 7.45x10 -10 S/m was determined for BuPTCD PVD films onto Au interdigitated electrodes (IDE-structured devices), which can be enhanced, under illumination, by two orders of magnitude (photoconductivity effect). As proof-of-concept, the IDE-structured devices are tested as gas sensor for trifluoroacetic acid.

Physical Vapor Deposited Films of a Perylene Derivative: Supramolecular Arrangement and Thermal Stability

“…This leads to the conclusion that the surface of the film is relatively smooth, despite the observed molecular aggregates. The same trend was found for other PVD films of perylene derivatives, such as bis butylimido perylene (BuPTCD) 29 and bis benzimidazo perylene (AzoPTCD), 14 which were deposited under similar experimental conditions, and for which the RMS roughness was found to be ca. 3% and 5% (for films thicker than 30 nm), respectively, of the PVD film thickness.…”

“…Therefore, one can infer the PhPTCD PVD film presents both J and H-aggregates. This trend is also observed for PhPTCD in the form of Langmuir-Blodgett film (LB), 18 in addition to other perylene derivatives forming either PVD 11,[29][30][31] or LB films. [32][33][34][35] The emission of the PhPTCD PVD films was investigated using the 514.5 nm excitation laser line, which spectrum for a 150 nm thickness film on quartz with a maximum at 689 nm shown in Figure 3.…”

“…Therefore, it can be concluded the PhPTCD PVD film presents an amorphous arrangement. It is interesting to mention the PVD films of BuPTCD 29 and AzoPTCD 14 present crystalline and amorphous arrangements, respectively, even though being deposited under similar experimental conditions.…”

“…chromophore plane preferentially parallel to the substrate surface; 15,[40][41][42][43][44][45] ii) edge-on, i.e. chromophore plane preferentially perpendicular to the substrate surface, standing either on the longer chromophore axis 14 or the shorter chromophore axis; 11,29 iii) chromophore plane tilted in relation to the substrate surface; 17,42 and iv) random molecular organization. 16,41 Usually, three vibrational modes are key to determine the perylene derivative molecular organization: symmetric and antisymmetric C=O stretching modes at 1657 and 1696 cm -1 , respectively, 40 which are parallel to the chromophore plane, and C-H wagging modes at 745 and 810 cm -1 , 40 which are perpendicular to the chromophore plane.…”

Perylene Diimide‐Based Electron‐Transporting Material for Perovskite Solar Cells with Undoped Poly(3‐hexylthiophene) as Hole‐Transporting Material

“…As an ew ETM for PVSCs, we first checked its absorption, thermostability, and electrochemical and charge-transportingc haracteristics. UV/Vis absorption spectra of TCl-PDI film and solutiona re shown in Figure 1b.T he absorption spectrum of TCl-PDI in solution mainly indicates p-p*e lectronic transitions associated with as eries of characteristicv ibronic structures at 400-750 nm, [53,54] whicha re 0-0, 0-1, and 0-2 p-p*e lectronict ransitions with absorption peaks at 518, 485, and 425 nm, respec-tively.T he absorption spectrum of the thin film shows broadening and redshifted absorption bands, in which the relative intensities of the vibronic structures are quite different from those of the solution sample. These changes in spectroscopic features indicateasignificant molecular interaction of TCl-PDI in the solid state similart op-p stacking.…”