Effect of morphology and surface treatment on the performance of ZnO nanorod-based dye-sensitized solar cells

The effect of morphology and surface treatment on the performance of solution-grown ZnO nanorods as an electrode in a dye sensitized solar cell is demonstrated. Treatment includes the addition of EosinY during growth, post growth NaOH-based treatment and the production of nanorod-nanoparticle hybrid structures. The electrodes were sensitized using the organic indoline dye DN216 and dye-sensitized solar cells were prepared. Charge transfer dynamics and light harvesting properties were studied by absorbance spectroscopy, I-V measurements, voltage-decay measurements and electrochemical impedance spectroscopy. The introduction of EosinY to the precursor solution was found to increase the diameter of the rods and to produce nano-scale roughness. This lead to an improvement in dye loading and surface passivation against recombination leading to both an increase in V-oc and Jsc of the device, compared to ZnO nanorods deposited without EosinY. Subsequent treatment of as-deposited ZnO nanorods in aqueous NaOH increased the surface area by producing tube-like nanostructures, without compromising the electron mobility. When compared to untreated nanorods, this morphology improves dye loading and increases electron lifetime, which then leads to a higher fill factor and V-oc. A significant increase in J(sc) and drastic decrease in V-oc are obtained for a hybrid electrode consisting of nanorods and nanoparticles which is both caused by a higher surface area and faster back-recombination. Highest efficiencies were obtained by post-deposition treated nanorod electrodes deposited from EosinY containing solutions. (C) 2019 Elsevier B.V. All rights reserved.