Cascading energy transfer is a usually undesired effect in organic-host guest systems that are designed for light-emitting purposes. Here we demonstrate a chemical approach to suppressing undesired energy transfer from the blue to the red emitter in multicomponent polymer blends. We have combined a red, green and blue emitting Ir-complex each with charge transporting molecules to a side-chain copolymer. The covalent attachment of the phosphorescent emitter is found to prevent cascading energy transfer through steric shielding. This approach approximately doubles the efficiency and brightness of polymer light emitting diodes.