We have developed 4-(bis(9,9-dimethyl-9H-flouren-2-yl)amino)benzoic acid (HC-Acid) to use as an alternative co-adsorbent to deoxycholic acid (DCA) in organic dye-sensitized solar cells (DSSCs). It has dual functioned effects, that is, the prevention effect of the π–π stacking of organic dye molecules like DCA and the light harvesting effect at shorter-wavelength regions. When the HC-Acid was used as the co-adsorbent onto the TiO₂ surface with the organic dye NKX2677 sensitized solar cell, an extremely high conversion efficiency of 9.09% was achieved under 100 mW cm⁻² AM 1.5G simulated light (J_sc = 18.01 mA cm⁻², V_oc = 0.663 V, and FF = 76.16). As we herein demonstrate, an increase in short-circuit photocurrent density (J_sc) of 20%, open-circuit photovoltage (V_oc) of 11% and overall conversion efficiency (η) of 38% occurred in comparison to the NKX2677 based solar cell. As a consequence, this new class of a low molecular weight organic co-adsorbent (HC-Acid) is a promising candidate as an alternative co-adsorbent with a new function not seen in DCA or CA derivatives for highly efficient dye-sensitized solar cells.