Interface Structures and Electronic States of Epitaxial Tetraazanaphthacene on Single-Crystal Pentacene

Abstract

The structural and electronic properties of interfaces composed of donor and acceptor molecules play important roles in the development of organic opto-electronic devices. Epitaxial growth of organic semiconductor molecules offers a possibility to control the interfacial structures and to explore precise properties at the intermolecular contacts. 5,6,11,12-tetraazanaphthacene (TANC) is an acceptor molecule with a molecular structure similar to that of pentacene, a representative donor material, and thus, good compatibility with pentacene is expected. In this study, the physicochemical properties of the molecular interface between TANC and pentacene single crystal (PnSC) substrates were analyzed by atomic force microscopy, grazing-incidence X-ray diffraction (GIXD), and photoelectron spectroscopy. GIXD revealed that TANC molecules assemble into epitaxial overlayers of the (010) oriented crystallites by aligning an axis where the side edges of the molecules face each other along the [1¯10] direction of the PnSC. No apparent interface dipole was found, and the energy level offset between the highest occupied molecular orbitals of TANC and the PnSC was determined to be 1.75 eV, which led to a charge transfer gap width of 0.7 eV at the interface.

Towards the Bisbenzothienocarbazole Core: A Route of Sulfurated Carbazole Derivatives with Assorted Optoelectronic Properties and Applications

“…1 H NMR (400 MHz, CDCl 3 ) δ (ppm): 8.19 (d, J = 7.9, 2H), 8.17 (d, J = 7.9, 2H), 7.67 (td, J = 7.6, 1.4 Hz, 2H), 7.60 (td, J = 7.4, 1.4 Hz, 2H), 7.25 (dd, J = 7.4, 1.4 Hz, 2H), 7.46 (s, 2H), 7.25 (dd, J = 7.9, 1.4 Hz, 2H), 4.32 (t, J = 7.2, 2H), 2.34 (s, 6H), 1.87 (m, 2H), 1.45-1.20 (m, 6H), 0.83 (t, J = 7.1 Hz, 3H). 13 [1]benzothieno[3,2-b:2',3'-h]carbazole (1a) 2b (200 mg, 0.379 mmol) and phosphorus pentoxide (27 mg, 0.19 mmol) were dissolved in trifluoromethanesulfonic acid (5.7 mL) and stirred at room temperature for 72 h. The crude was poured into a mixture of ice-water (50 mL) and the resulting yellow precipitate was filtered. The precipitate was then dissolved in pyridine (30 mL) and refluxed overnight.…”

“…1 H NMR (400 MHz, CDCl 3 ) δ (ppm): 8.08 (s, 2H), 7.45 (d, J = 7.9 Hz, 4H), 7.28 (d, J = 7.9 Hz, 4H), 7.28 (s, 2H), 3.79 (s, 3H), 2.69 (t, J = 7.8 Hz, 4H), 2.41 (s, 6H), 1.69 (m, 4H), 1.45-1.29 (m, 12H), 0.91 (t, J = 6.9 Hz, 6H). 13 2.1.7. Synthesis of 2,7-bis(4-hexylphenyl)-9-methyl-3,6-bis(methylsulfinyl)-9H-carbazole (3b) 3a (200 mg, 0.337 mmol) was dissolved in a mixture of glacial acetic acid and chloroform (1:1 v/v, 24 mL).…”

“…1 H NMR (400 MHz, CDCl 3 ) δ (ppm): 8.27 (dd, J = 8.0, 1.5 Hz, 2H), 8.18 (d, J = 1.5 Hz, 2H), 7.69-7.63 (m, 4H), 7.59-7.54 (m, 2H), 7.51 (d, J = 8.0 Hz, 4H), 7.48 (dd, J = 7.5, 1.3 Hz, 4H), 4.38 (t, J = 7.4 Hz, 2H), 2.59 (s, 6H), 2.00-1.91 (m, 2H), 1.50-1.30 (m, 6H), 0.90 (t, J = 7.1 Hz, 3H). 13 (17 mL) and cooled at 0 • C. Then, hydrogen peroxide (35%, 93 µL, 1.1 mmol) was added carefully and the mixture was stirred overnight at room temperature. The solvents were removed under reduced pressure.…”

“…Pentacene is probably one of the best representatives of this type of compound. Despite its disadvantageous lack of stability, it still stands among the top organic semiconductors, with reported charge mobility values up to 35 cm 2 V −1 s −1 determined by space-charge-limited current measurements [13,14].…”

“…V −1 s −1 determined by space-charge-limited current measurements [13,14]. The inclusion of heterocycles into the pentacene backbone has been a frequently exploited strategy in the search for novel materials with enhanced stability and performance.…”