||One of main reasons for the low performance of dye-sensitized solar cells (DSSCs) is a recombination of injected electron with I3- at the surface of TiO2 nanoparticles. To retard recombination, we used polyamidoamine (PAMAM) dendrimer and polyester hydroxyl acetylene bis (hydroxymethyl) propanoic acid dendron (Dendron) as co-adsorbent to form a barrier layer on TiO2 nanoparticles. PAMAM dendrimer has many carboxyl surface groups, and Dendron has a carboxyl group at core. DSSC containing the G 1.5 PAMAM dendrimer showed the highest JSC and η. When Dendron was used as co-adsorbent, JSC and η were increased, but VOC was nearly constant. Then we also studied effect of various concentrations of PAMAM dendrimer and Dendron. Decrease of recombination was confirmed by EIS measurement. The variation of JSC was consistent with the results of IPCE measurement. The effect of coverage and functional group of co-adsorbent on the performance of DSSC was investigated.