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.