An exceptional approach of appending tris(1,10-phenanthroline)cobalt(II)/(III)bis/tris(hexafluorophosphate) and synthesized tetramethyl benzidine-based thiourea derivatives as novel additives with hydroxypropyl cellulose are used to construct a gel polymer electrolyte for DSSC. The thiourea derivatives are synthesized using the cost-effective method. The synthesized derivatives are confirmed by H-1, C-13 NMR and mass spectroscopy. The conductivity, surface and redox potential of thiourea derivatives doped Co2+/Co3+ redox electrolytes are scrutinized by impedance spectra, FTIR, UV, XRD. A density functional theory method with full geometry optimization is used to elucidate the adsorption of the symmetrical thiocarbamides on TiO2 (101) surface progressing with electron donating/accepting groups. All the organic compounds display a negative shift on the TiO2 Fermi level simultaneously by adsorption and rebutted as an escalated additive in stable Co(II/III) phen redox electrolyte of the dyesensitized TiO2 solar cell. This impulse effect influences the sorbate dipole moment component normal to TiO2 surface plane; further, the stable redox mediator and hydroxypropyl cellulose deliver a good performance in a dye-sensitized solar cell. The newly synthesized thiourea derivatives doped Co2+/Co3+ with hydroxypropyl cellulose reports high solar to electric conversion, particularly 1,1'-(3,3',5,5'-tetramethyl-[1,1'-biphenyl]-4,4'-diyl)bis(3-(3,4,5-trimethoxy phenyl)thiourea) (additive-6) doped redox electrolyte shows an outstanding efficiency (sic) of 9.1% under the sunlight irradiation of about 70 mW/cm(2). (C) 2018 Elsevier Ltd. All rights reserved.