Generic packing motifs in vapor-deposited glasses of organic semiconductors.

Bagchi, Kushal; Gujral, Ankit; Toney, M F; Ediger, M D · Soft Matter · 2019

basic_science · Level V

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Abstract

We study the structure of vapor-deposited glasses of five common organic semiconductors as a function of substrate temperature during deposition, using synchrotron X-ray scattering. For deposition at a substrate temperature of ∼0.8T<sub>g</sub> (where T<sub>g</sub> is the glass transition temperature), we find a generic tendency towards "face-on" packing in glasses of anisotropic molecules. At higher substrate temperature however this generic behavior breaks down; glasses of rod-shaped molecules exhibit a more pronounced tendency for end-on packing. Our study provides guidelines to create face-on and end-on packing motifs in organic glasses, which can promote efficient charge transport in OLED and OFET devices respectively.