The energy levels (HOMO, LUMO) of the conjugated polymer are tuned independently, so that an energy match on both sides of the device can be accomplished while keeping the emission color in the blue region. Such polymers can be formed by polymerization of a mixture of monomers. The mixture of the monomers contains at least one monomer having an electron-deficient group sandwiched by two aromatic hydrocarbon groups ("Monomer (I)") and at least one hole transporting ("HT") monomer. The mixture of monomers may also contain a solubility enhancement ("SE") monomer and/or a Branching Monomer. Such polymers can be used in fabricating light emitting diodes to achieve some of the best device performance to date including high efficiency and blue color purity.