Poly(p-phenylene vinylene) (PPV, or polyphenylene vinylene) is a conducting polymer of the rigid-rod polymer host family. PPV is the only polymer of this type that has so far been successfully processed into a highly ordered crystalline thin film. It is prepared by thermal processing of a precursor polymer. By careful control of the processing it is possible to influence the structure and morphology of the film. Polyphenylene vinylene is capable of electroluminescence, leading to applications in polymer-based organic light emitting diodes. PPV was used as the emissive layer in the first polymer light-emitting diodes. Devices based on PPV emit yellow-green light, and derivatives of PPV obtained by substitution are often used when light of a different color is required.