This work reports on the successful exploitation of a nanocomposite comprising HO-functionalized multi-walled carbon nanotubes decorated with electrochemically-grown rhodium nanoparticles (MWCNT-OH/Rh) as a cathode material in dye-sensitized solar cells (DSCs). Electrochemical investigations represent a large electroactive surface area, 0.547 cm(2), for the nanocomposite electrode, which is 7.5 times more than the exposed geometric one. The electrochemical impedance spectroscopy (EIS) discloses a 14-time smaller charge-transfer resistance (R-CT) at the nanocomposite electrode compared to the bare electrode. Furthermore, the computational calculation performed by dispersion-corrected density functional theory (DFT-D) signifies that the proposed nanocomposite contains the highest occupied molecular orbital (HOMO), the lowest unoccupied molecular orbital (LUMO), and the bandgap energy values of -6.77, -5.84, and 0.93 eV, respectively, suggesting the high conductivity for the nanocomposite. Based on the calculation results, the manuscript discusses the main charge-transfer mechanism of this device. Under the standard condition, consists of Air Mass 1.5 (AM 1.5) illumination at 100 mW cm(2), the DSC equipped by N719-sensitized TiO2 photoanode and the nanocomposite counter electrode shows significant improvements in photovoltaic parameters including short-circuit current density (J(SC)), power-conversion efficiency (PCE), and incident photon-to-current conversion efficiency (IPCE) as 27.29 mA cm(-2), 11%, and 85%, respectively. (C) 2019 Elsevier Ltd. All rights reserved.