NOVELTY - The copolymer comprises (by residual monomeric units) 9-substituted and/or 9,9-disubstituted fluorene moieties and at least two other monomer units containing delocalized pi-electrons.    USE - As active components in electronic devices including light emitting diodes, photocells, photoconductors and field effect transistors.    ADVANTAGE - The light emitting diodes (LED) containing (1) shows a luminance of 4000 Cd/m2 at lower voltage and higher efficiency as compared to LED not containing (1).    DETAILED DESCRIPTION - A copolymer comprises:    (a) 9-substituted and/or 9,9-disubstituted fluorene monomeric units (at least 10%); and    (b) two other monomeric moieties having delocalized pi-electrons (at least 1%), where the two moieties are selected from a group having hole transporting properties and/or electron transporting properties and if both the two other moieties are groups group having hole transporting properties, then at least one of the moieties is derived from stilbene, 1,4-diene without electron-withdrawing substituents, N,N,N',N'-tetraarylbenzidine, N-substituted-carbazole, diarylsilane or thiophene/furan/pyrrole without electron-withdrawing substituents.    INDEPENDENT CLAIMS are also included for the following:    (A) a composition comprising a blend of a first polymer selected from a copolymer as above and a second polymer;    (B) a light emitting diode comprising an anode, a cathode and at least one film located between the anode and cathode;    (C) a photocell comprising at least one film;    (D) a metal-insulator semiconductor field effect transistor comprising an insulating layer, at least one film deposited onto the substrate, a source electrode connected to a first portion of at least one film, a drain electrode connected to a second portion of at least one film and a gate electrode located on the opposite side of the insulating layer from at least one film; and    (E) a copolymer comprising one and at least 1% of monomeric units derived from optionally substituted benzene, naphthalene or biphenylene. If a substituted compound is used, the substituents are selected from 1-12C alkyl or alkoxy or 6-10C aryl or aryloxy.