Organic semiconductor solution-processable

The development of solution processing for semiconductor materials has mostly focused on organic semiconductors.3 5 Organic transistors can be... 

Flat-Panel Displays Made with Solution-Processible Organic Semiconductors.25... 

FLAT-PANEL DISPLAYS MADE WITH SOLUTION-PROCESSIBLE ORGANIC SEMICONDUCTORS... 

Sakanoue T, Sirringhaus H (2010) Band-like temperature dependence of mobility in a solution-processed organic semiconductor. Nat Mater 9 736... 

Organic functionalization reactions have been carried out both in vacuum and in solution. The vacuum studies typically use the clean, reconstructed (100) or (111) crystal faces of the semiconductor, and the reactants are dosed in the gas phase. Because the semiconductor surfaces are readily oxidized and otherwise contaminated in air or solution, the usual approach for solution-based functionalization is to first passivate the semiconductor (e.g., with hydrogen or halogens) through solution processing, then carry out a reaction which replaces the passivating layer with the organic molecules. 

Most current solution-processable organic semiconductor compounds fail to satisfy all these requirements simultaneously. 

Molecular self-organization in solution depends critically on molecular structural features and on concentration. Molecular self-organization or aggregation in solution occurs at the critical saturation concentration when the solvency of the medium is reduced. This can be achieved by solvent evaporation, reduced temperature, addition of a nonsolvent, or a combination of all these factors. Solvato-chromism and thermochromism of conjugated polymers such as regioregular polythiophenes are two illustrative examples, respectively, of solubility and temperature effects [43-45]. It should therefore be possible to use these solution phenomena to pre-establish desirable molecular organization in the semiconductor materials before deposition. Our studies of the molecular self-assembly behavior of PQT-12, which leads to the preparation of structurally ordered semiconductor nanopartides [46], will be described. These PQT-12 nanopartides have consistently provided excellent FETcharacteristics for solution-processed OTFTs, irrespective of deposition methods. 

An alternative route to solution-processible organic semiconductors is to use precursors to small molecule semiconductors, such as pentacene [59] or tetrabenzo-porphyrin [60], which can be converted into their fully conjugated, insoluble form by thermal or irradiative [61] treatment on the substrate. Pentacene precursors have been shown to yield field-effect mobilities of 0.01-0.1 cm2 V-1 s 1 [62], and 0.1-0.8 cm2 V-1 s 1 [63] after thermal conversion at 150-200 °C. Small molecule organic semiconductors can also be rendered solution processible by attachment of flexible side chains [64-66], Due to the relatively low solubility of these molecules the growth of uniform thin films of these molecules remains challenging, however. 

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