Abstract: The surface photovoltage spectra of thin films of poly［2-methoxy-5-(2-ethyl-hexyloxy)-1, 4-phenylene vinylene］ were determined in order to determine their localized transition（350~420 nm）and delocalized transition（420~600 nm）. The experiments demonstrated that the localized transition would be attributed to the electronic transition from the valence band to a local state in the conduction band.

Key words: MEH-PPV, surface photovoltage, local state