Copolymers of carbazole and fluorene with dendrimer side groups were synthesized using Suzuki Coupling and Horner-Wadsworth-Emmons reaction. Furthermore, 2mol% of benzothiadiazole and 1,4-bis(2-bromostyryl)benzene (OPV) were introduced into the copolymers. The effects of these two groups on optical and electrical properties of the copolymers were investigated. Copolymers with dendrimer side groups have higher Tg since the huge side groups make it difficult to rotate and move. At last, polymer light emitting diodes were fabricated and the performance of the devices was thoroughly investigated.