We report a molecular engineering study on optical, structural and electrical properties of seven silole derivates aimed at enhancing the charge carrier balance in single-layer devices. By functionalizing two hole-transporting groups, dipyridylamine and anthracene, on the silole ring, we have investigated the influence of both substituents on the hole current. We have concluded that in contrast to dipyridylamine groups, anthracene groups decrease the charge carrier balance since the latter groups not only increase the hole current but also electron contribution. Mixing these hole-transporting groups and doubling their number lead to a novel silole becoming a very efficient emissive layer exhibiting threshold voltage below 3 V and luminous efficiency Le = 0.8 cd A-1 at 7 V.