  The authors synthesized three new silole derivs. with incrementally flexible
structure to tune their packing ability and therefore study the influence of
the mol. organization in single-layer OLEDs. This architecture was chosen since
the absence of org. layers interfaces allows a better evaluation of the role of
the mol. arrangement in the active layer. The examn. of the EL properties gives
evidences of the prominent role of the mol. organization on the OLED
efficiency. A cryst.-like organization of the mols. allows high c.d. 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 mols. allows better performances by avoiding
unfavorable p-stacking, while keeping good intermol. orbital overlaps to
support charge carrier transport.
