Electroluminescence of thin films of poly(3,3-phthalidylidene-4,4'-bip
henylylene) (PPB) and poly(3,3-phthalidylidene-2,7-fluorenylylene) (PP
F) was studied. In both cases, electroluminescence was found to be of
a threshold origin. Emission maxima and quantum efficiencies for PPB a
nd PPF are 490 and 525 nm, 0.01 and 0.1%, respectively. The electrolum
inescent characteristics were found to be strongly dependent on the po
lymer used.