The polar molecules including ferroelectric materials with large dipole moments have been applied as interracial layers to increase the efficiency of organic solar cells by increasing the bounded charge separation, tuning the energy levels etc.Here we report a small polar molecule 2-cyano-3-(4-(diphenylamino)phenyl)acrylic acid (TPACA) that can be either blended in the active layer or at the interface of polymer and electrode to increase the efficiency of the solar cell devices after poling.The dipoles of TPACA can be aligned by applied bias.It was found that the built-in potential of the device increased by 0.2 V after poling under negative bias.Blending TPACA into the active layer has shown to be a universal method to increase the efficiency of polymer solar cells.The efficiency is increased by 30％-90％ for all the polymer:fullerene systems tested, with the highest efficiency reaching 7.83％ for the poly [4,8-bis-(2-ethyl-hexyl-thiophene-5-yl)-benzo[1,2-b:4,5-b]dithiophene-2,6-diyl]-alt-[2-(2-ethyl-hexanoyl)-thieno[3,4-b]thiophen-4,6-diyl]: [6,6]-phenyl-C71-butyric acid methyl ester (PBDTTT-CT:PC7oBM) system.