Abstract: In this work, we systematically studied the optoelectronic properties of four poly(3-butylthiophene)(P3BT) with different functional end-groups. The end-groups were found to be detrimental to the crystallization of P3BT. Nevertheless, the end-groups could modify the surface energy of P3BT and therefore achieve the tunable miscibility and film morphology of P3BT∶PCBM blends. The solar cell devices based on these P3BTs with functional end-groups as donor materials have been fabricated and tested. We demonstrated that the allyl-terminated P3BT has relative higher crystallinity. And the appropriate miscibility of allyl-terminated P3BT and PCBM could lead to an ideal micro phase separation morphology of P3BT∶PCBM in the active layer of solar cell device. The corresponding photovoltaic device performance could reach 3.1% which is 35% higher than that of conventional device using bromide-terminated P3BT.

Key words: end-group, poly(butylthiophene), miscibility, optoelectronic property