Photoluminescence (PL) and electroluminescence (EL) properties of a polyp-phenylenevinylene) (PPV) derivative containing crown ether (C-PPV) were investigated. The PL quantum yield as high as 90% in solution and a temperature independence were observed. We infer that the surrounding side group, crown ether, effectively confines the excitons for radiative emission. The planar structure of crown ether also increases interchain interactions in the polymer and induces the formation of aggregation, which makes the PL spectrum of its solid film red-shifted. Through the Langmuir-Blodgett method, the evidence for aggregate formation is demonstrated: The polymer has been used in light emitting diodes. Using C-PPV as an emitting layer, the single layer device shows a low turn-on voltage (ca. 3 V), whereas the double layer device with a structure of ITO/C-PPV/tris(8-hydroxyquinolinato)aluminum (Alq(3))/Al shows a moderate EL performance with a brightness of 730 cd/m(2) and an external efficiency of 0.04%.