An electron acceptor polycondensation polymer of the formula (I) ##STR1## wherein R.sub.1 is a hydrogen atom or an alkyl group, an aryl group or an aralkyl group having not more than 15 carbon atoms; C.sub.m is a divalent connecting group; FLac is an electron acceptor group having a fluorene nucleus as its basic structure; X and Y are a carbonyl group or an acid amide group forming a urethane linkage with the oxygen atom of the diol; R.sub.2 is a bifunctional organic residue having not more than 20 carbon atoms, n is a number greater than 10 which represents the degree of polycondensation of the resultant polycondensation polymer.