Study of the influence of the molecular organization on single-layer OLEDs' performances

We have synthesized three new silole derivatives with incrementally flexible structure to tune their packing ability and therefore study the influence of the molecular organization in single-layer OLEDs. This architecture was chosen since the absence of organic layers interfaces allows a better evaluation of the role of the molecular arrangement in the active layer. The examination of the EL properties gives evidences of the prominent role of the molecular organization on the OLED efficiency. A crystalline-like organization of the molecules allows high current density but low luminance efficiency since an excessive electron current flow is involved compared to the hole one, and the recombination rate is poor. On the contrary, disordered assemblies of molecules allows better performances by avoiding unfavourable Tr-stacking, while keeping good intermolecular orbital overlaps to support charge carrier transport. (C) 2007 Elsevier B.V. All rights reserved.