Self-Organization in Thin Films of Liquid Crystalline Perylene Diimides

A family of liquid crystalline organic semiconductors based on perylene-3,4,9,10-tetracarboxyldiimide is introduced. The thermal tansitions, self-organizing behavior, and change in photophysical properties upon self-organization of one member of the family are described. Red, polycrystalline thin films of spin-coated N,N'-bis [3-[2-(2-methoxyethoxy)ethoxy]-2-propoxy]propyl]peryline-3,4,9,10-tetracarboxyldiimide spontaneously form a highly crystalline black phase after about 24 h. The quantum yield for fluorescence from the black phase is enhanced 7-fold, and the width (fwhm) of the emission band is decreased by more than a factor of 2, with respect to the red phase. The self-organization process appears to decrease spontaneously both the energetic disorder and thedensity of exciton quenching sites in the film.