A series of naphthyl-substituted poly(p-phenylenevinylene)s (2N-PPV, 4N-PPV, and NAP-PPV) are synthesized and characterized. The polymers possess excellent solubility, high molecular weights, good thermal stability, and high photoluminescence efficiencies. Proton NMR measurements indicate that all the polymers have negligible amounts of tolane–bisbenzyl defects along the polymer main chain as a result of the steric bulk imposed by the naphthalene side chain. Polymer light-emitting diodes utilizing the polymers as the emissive layer with a configuration of indium tin oxide/poly(3,4-ethylenedioxythiophene)/polymer/Ba/Al emit blue-green to yellow-green light. The current–voltage–luminance characteristics of the indium tin oxide/poly(3,4-ethylenedioxythiophene)/polymer/Ba/Al devices are shown.