Refractive Index Measurements of Well-Defined Polygon Crystals of Thiophene/Phenylene Co-Oligomers

Abstract

We have improved the crystal growth methods of thiophene/phenylene co-oligomers (TPCOs). The crystal growth was carried out in a liquid phase. The resulting crystals were well defined in thin polygons with several pairs of parallel crystal faces that function as optical mirrors. This produces interference fringes in the emission and reflectance spectra, enabling us to determine the anisotropic refractive indices. From among TPCOs we chose 5,5 0 -bis(4-biphenylyl)-2,2 0 -bithiophene (BP2T) and its methoxy derivative 5,5 0 -bis(4 0 -methoxybiphenyl-4-yl)-2,2 0 -bithiophene (BP2T-OMe). #

Refractive Index Dispersion and Anisotropic Group Refractive Indices of Rubrene Crystals

“…For measurements we laminated the crystals on a silicon wafer substrate covered with a silicon dioxide layer of 300 nm in thickness. We observed the size and shape of the crystals using a NIKON ECLIPSE LV100POL polarizing microscope with an EXFO X-Cite 120 mercury lamp (white light: 294.5 to 812.5 nm) [13]. Thickness measurements and X-ray diffraction (XRD) measurements were performed in the manner same as before [17].…”

“…We measured the interference fringes in both the reflectance and emission spectra using the methods described in the literature [11][12][13]. For both the measurements we irradiated incident lights perpendicularly to the substrate plane.…”

“…a pair of reflecting mirrors). Using a SOLAR TII MS7504 monochromator spectrograph we acquired the emission spectra occurring from the crystal along the direction perpendicular to the resonator mirrors [11,13].…”

“…These facets form another vertical resonator. The reflected light (570−820 nm) from the crystal was polarized in the same direction as the incident light and was detected with a Hamamatsu Photonics PMA-11 photonic multichannel analyzer [12,13].…”

“…Broadband nature of these spectra enables us to investigate the refractive index relevant to the emission wavelength regions. By applying this method to crystals of thiophene/phenylene co-oligomers, we have determined their refractive indices [11][12][13]. In the present studies, on the basis of the above method, we have evaluated the dispersions and anisotropic group refractive indices of the rubrene crystals.…”