Toward Single Crystal Thin Films of Terthiophene by Directional Crystallization Using a Thermal Gradient

Abstract

A method for the preparation of uniaxially oriented thin films of terthiophene (20–50 μm thick) is introduced. It relies on the crystal growth with a Bridgman-type process that decouples nucleation and growth phenomena. An effective thermal gradient of 6–11.6 °C/mm has been used in which the sample (terthiophene powder deposited on either glass or fluorinated glass substrates) is displaced from a hot zone to a cold zone at a constant rate of 2.5–5 μm/s. The size and orientation of crystals have been investigated by polarized optical microscopy and X-ray diffraction measurements. A coexistence of two polymorphs of terthiophene has been observed, but optimal gradient conditions enabling the selective crystallization of only the room temperature stable polymorph have been found. Terthiophene films deposited on fluorinated glass substrates and crystallized using the thermal gradient technique show a stronger tendency to polymorphism and random orientation of crystallites for all gradient conditions tested. The monoclinic unit cell (a = 15.410 Å, b = 5.709 Å, c = 26.052 Å, β = 97.77°) of the room temperature phase orients its ab plane parallel to the substrate. Pole figures demonstrate the growth of uniaxially aligned crystals with the [100] and [−100] directions along the gradient axis. Finally, a tentative explanation for this peculiar in-plane orientation is given based on crystal morphology calculations.

Solution‐Grown Organic Single‐Crystalline p‐n Junctions with Ambipolar Charge Transport

“…For both C8‐BTBT and C 60 solutions, aligned ribbon crystals were grown using the DPC method . ( Figure A,B,E,F) Similar to other aligned crystallization directed by concentration and/or temperature gradients, crystals were aligned during the directional droplet receding driven by surface tension ( Figure A). The thickness of the ribbon crystals depends on the concentration of the semiconductor solutions.…”

Preparation of Single‐Crystalline Heterojunctions for Organic Electronics

“…Among them, droplet‐pinned crystallization (DPC) is a facile method to prepare, from solutions, well‐aligned organic single crystals in a large area . Based on an evaporating solution droplet pinned on a substrate, directional and stable receding of the droplet induces the aligned crystallization of organic semiconductors, similar to other alignment mechanisms in varied solution methods . A variety of crystals have been grown using this method and four examples are shown in Figure .…”

Obtaining the lattice energy of the anthracene crystal by modern yet affordable first-principles methods

“…Despite the weakness of these forces, they really matter since any chemical functionalization of the molecular backbone might alter the mode of packing [7][8][9] and thus all the intended properties. On the other hand, polymorphism is a common issue affecting drug discoveries, crystal engineering or final composition of samples, demanding also the greatest possible accuracy to energetically rank the competing structures, which in many cases differ by just few kJ/mol [10][11][12][13][14][15][16][17].…”