A composition comprising a
polymer comprising a
repeat unit of Formula I.: wherein R<1 >is independently in each occurrence H, C1-40 hydrocarbyl or C3-40 hydrocarbyl containing one or more S, N, O, P or Si atoms, or both of R<1 >together with the 9-carbon on the
fluorene, may form a C5-20 ring structure which may contain one or more S, N, or O atoms; R2 is independently in each occurrence C1-20 hydrocarbyl, C1-20 hydrocarbyloxy, C1-20
thioether, C1-20 hydrocarbyloxycarbonyl, C1-20 hydrocarbylcarbonyloxy, or cyano; a is independently in each occurrence, 0 or 1; X is O, S, SO2, C(R<3>)2 or N-R<3 >wherein R<3 >is
aryl or substituted
aryl of C6 to C40, aralkyl of C6 to C24, or
alkyl of C1 to C24. Preferably R<3 >is
aryl of C6 to C24 and more preferably R<3 >is an alkylated aryl group of C6 to C24; Ar is an aryl or heteroaryl group of C6 to C40 or substituted aryl or heteroaryl group of C6 to C40, preferably C6-C24, and most preferably C6-C14. Y is a conjugated
moiety that can vary in each occurrence of the
repeat unit.