Molecular Modification of 2,7-Diphenyl[1]benzothieno[3,2-<i>b</i>]benzothiophene (DPh-BTBT) with Diarylamino Substituents: From Crystalline Order to Amorphous State in Evaporated Thin Films
Introduction of diarylamino substituents on 2,7-diphenyl[1]benzothieno[3,2-b]benzothiophene (DPh-BTBT) caused morphological change in the evaporated thin-film state: from highly crystalline films with edge-on molecular orientation for DPh-BTBT to amorphous films for the diarylamino derivatives. The former was unsuitable as a hole-transporting layer in organic light-emitting diodes (OLEDs), whereas the latter acted as a superior hole-transporting layer in multilayered OLEDs.