Electron Transport in a Water-Soluble Liquid-Crystalline Perylene Bisimide

Abstract

Perylene bisimide (PBI) derivatives are n-type semiconductor materials widely used in a variety of optoelectronic devices. Great efforts have been devoted to the synthesis of soluble PBIs to allow processing by inexpensive solution-state methods. Recently, water-soluble compounds are receiving special attention for their potential in the fields of biology and “green” organic electronics. There is also a growing interest in the development of liquid crystalline PBIs, in order to improve the supramolecular organization and hence the transport performance. This work reports the first investigation of the mobility measured by the time-of-flight technique and the photoconductive response of the perylene derivative N,N′-bis[1-(2,5,8,11-tetraoxadodec-1-yl)-3,6,9,12-tetraoxatridec-1-yl]-perylene-3,4:9,10-bis(dicarboximide) (PBI-W), which is simultaneously water-soluble and liquid-crystalline. For comparison purposes, a parallel investigation with the commercial derivative N,N′-bis(1-hexylheptyl)-perylene-3,4:9,10-bis(dicarboximide) (PBI-C6), which is neither liquid-crystal nor water-soluble, has also been carried out. The conductive spectral response and the mobility dependence on the strength of the applied electric field were studied in order to optimize mobility measurements conditions. The mobility was determined as a function of temperature from room temperature (22 °C) up to 100 and 120 °C, for PBI-W and PBI-C6, respectively. Results are discussed in correlation with the crystalline or liquid-crystalline character phase of the material.