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Among organic materials vitrification for many years was regarded mainly as a privilege of polymers. However, recently a lot of attention is paid to organic low molar mass compounds that readily form glasses above room temperature. Such compounds are called molecular glasses or amorphous molecular materials. Among these materials the most widely studied are charge‐transporting molecular glasses used in copiers and laser printers, organic light‐emitting diodes, photovoltaic devices, and as photorefractive materials. Two types of molecular glasses, i.e., p‐type (hole‐transporting), and n‐type (electron‐transporting) are discussed. Work of the laboratories of the authors is emphasized. In addition, an overview of current and potential applications for these materials is presented.

Homogeneous alignment of poly(9,9-dioctylfluorene) films on thin layers of rubbed precursor-route poly(p-phenylenevinylene) allows the construction of light-emitting diodes that emit highly polarized blue light (λem=458 nm). The rubbed poly(p-phenylenevinylene) acts as an effective hole-injecting alignment layer. Annealing of poly(9,9-dioctylfluorene) in its nematic phase followed by rapid quenching orients the polymer as a glassy monodomain on the alignment layer and gives devices with a polarization ratio of 25:1 and a luminance of up to 250 cd/m2.

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Six novel star-shaped compounds with a triphenylamine core and carbazole or fluorene sidearms have been synthesized by Suzuki cross-coupling. The star-shaped molecules are able to form molecular glasses. They were characterized regarding their thermal, optical, and electrochemical properties. The new compounds were tested as organic semiconductors in solution processed organic field-effect transistors (OFETs). Mobilities of 3 × 10 -4 cm 2 /(V s), high on/off ratios of up to 10 5 , and low threshold voltages were obtained. The new materials show very small hysteresis and an exceptionally high stability under ambient conditions.