In this work, we report comprehensive photovoltaic investigation of four structurally simple D-A configured organic dyes, A(1-4) as active co-sensitizers in DSSCs sensitized with well-known Ru (II) based N3 dye. These effective co-sensitizers (A(1-4)) comprise N,N-dimethylaniline ring as donor scaffold linked with electron withdrawing functionalities, viz. barbituric acid (A(1)), N,N-dimethyl barbituric acid (A(2)), thiobarbituric acid (A(3)), and N,N-diethyl thiobarbituric acid (A(4)) as acceptor/anchoring units. In the present study, for the first time we have demonstrated the profound role of various simple organic molecules carrying different heterocyclic anchoring units on the photovoltaic parameters of the N3 sensitized devices. Also, the effect of concentration of sensitizer/co-sensitizers on the device performance characteristics has been investigated in depth. From the results, it is evident that, the device fabricated using co-sensitizer A(2) carrying N,N-dimethyl barbituric acid along with sensitizer N3 in all concentrations outperformed when compared to N3 alone or other co-sensitizers. Interestingly, the best photovoltaic performance was obtained for the co-sensitized device fabricated using 0.3 mM co-sensitizer A(2) along with 0.2 mM of N3 sensitizer. It displayed PCE of 7.02% with J(sc) of 15.27 mA.cm(-2), V-oc of 0.671 V and FF of 68.47%. Thus, the observed results have thrown new light upon the device optimization to yield DSSCs with improved performance by the selection of matchable co-sensitizers at appropriate concentrations.