Through a combined experimental and theoretical investigation we have shown that the efficiency of charge injection in dye-sensitized solar cells constituted from dyes having a single carboxylic group is determined by the extent to which the lowest unoccupied molecular orbital (LUMO) of the dye falls on its anchoring group. This conclusion was brought by calculating the LUMO surface of three indoline dyes and comparing the conversion efficiency of dye-sensitized solar cells fabricated using those dyes. The Ruthenium based N3 dye was used as standard both in the calculation and experiment.