The luminescent properties of conjugated polymers are seriously affected by concentration of the conjugated chains and the degree of polymer chain packing. We examined the effect of nanoporous morphology in the emitting layer of poly[2-methoxy-5-(2'-ethylhexyloxy)-1,4-phenylene vinylene] to hope that it would prevent polymer chain packing so that effectively decrease interchain interaction caused by interchain species and aggregates. High luminance is obtained at relatively low current density since the annihilation of singlet excitons is decreased. Redshifted emission due to the interchain aggregates and excimers are also suppressed, so that the color purity of the devices is greatly improved. (c) 2005 American Institute of Physics.