Two dimensional conjugated polymers have emerged as excellent polymer donor components in recent years. Here, all-polymer solar cells based on two conjugated side-chain isolated polythiophene derivatives (PT4TV and PT4TV-C) as donors and perylene diimide (PDI)-based polymer (PPDI-DTT) as acceptor are fabricated and investigated in detail. The structure similarity of the two polymers provides more insightful structure-property relationships. PT4TV based device displays a power conversion efficiency (PCE) of 0.99%, higher than that of PT4TV-C based device (0.55%). The high fill factor of larger than 50% in PT4TV based device is ascribed to the balanced hole and electron mobility of the donor and the acceptor. By adding chloronaphthalene solvent in PT4TV: PPDI-DTT solution, the PCE of PT4TV based solar cells is enhanced to 1.17%. Such improvement is interpreted in terms of the refined morphology of the film and ideality factor of the solar cell diode. (C) 2013 Elsevier B.V. All rights reserved.