The organic semiconductor polymers relates to the synthesis of a carbazole-based ladder polymer. The synthesis of the ladder polymer includes forming a precursor conjugated polymer by Suzuki step growth polymerization of 2,7-dibromocarbazole with 1,4-dibromo-2,5-divinylbenzene, followed by end capping with 2-bromostyrene and 2-vinyl-phenylboronic acid. Then, the pendent vinyl groups are closed by ring-closing olefin metathesis to obtain the ladder polymer.