Charge‐transporting polymers and molecular glasses for optoelectronic applications

Abstract Organic charge transport materials used in optoelectronic devices such as electrophotographic photoreceptors, light emitting diodes, solar cells, photorefractive materials can be devided into polymers, molecularly doped polymers and molecular glasses. Among charge‐transporting polymers hole‐transporting polymers are the most widely used and studied. An aromatic amino group is a common feature of many known charge‐transporting polymers. Almost all practical systems used in electrophotography belong to this category. Organic low‐molar‐mass compounds with stable solid amorphous phase above room temperature are called molecular glasses, amorphous molecular materials or low‐molar‐mass glasses. A real explosion of interest in organic electronically active low‐molar‐mass glass‐forming materials occurred after the discovery of high performance multilayer electroluminescent devices prepared from vacuum‐sublimed organic dye amorphous films. In this presentation the recent results of the work on the synthesis and properties of charge‐transporting polymers and molecular glasses performed in the author's laboratories are reviewed. The main attention is paid to the synthesis and studies of hole‐transporting polymers and molecular glasses. In the design and synthesis of these materials aromatic amino groups such as carbazolyl, tripehenylamino, phenothiazinyl and hydrazone moieties, have been used as the main building blocks. The properties of the charge‐transporting compounds synthesized are reported. Ionization potentials established by the electron photoemission in air technique range from 5.00 to 5.60 eV. Hole drift mobilities in the amorphous films of some hydrazones and aromatic amines approach 10 −2  cm 2 /V sec at high electric fields as revealed by the time‐of‐flight technique. Copyright © 2006 John Wiley & Sons, Ltd.