A series of cross-linked polythiophene derivatives (P1-4) are synthesized by adding different ratio (0, 2, 57 and 10%) of conjugated cross-linker via a Stille coupling reaction. From P1-4, with the increase of the content of the conjugated bridges, the UV-visible absorption peaks of the polymers were shifted towards blue and their electrochemical bandgap increased. The hole mobilities of P1-4 as determined from the SCLC model are 5.23 x 10(-6), 1.28 x 10(-4) 7.01 X 10(-3), and 2.34 x 10(-5) cm(2). V-1 . s(-1), respectively. The PCEs of the polymer solar cells based on P1-4 are 0.37, 1.05, 1.26, and 0.78%, respectively. The improvement of PCE of the devices based on P2-4 compared with that of P1 may be due to the increase of hole mobility.