Oxygen ion-beam irradiation of TiO₂ films reduces oxygen vacancies and improves performance of dye-sensitized solar cells

Abstract

Oxygen vacancy-related surface defects on porous TiO 2 films were reduced by oxygen ion-beam treatment, and the effect of such defects on the performance of dye-sensitized solar cells was examined. An oxygen ion-beam treatment of a TiO 2 film caused a significant decrease in particle agglomeration and an increase in surface area of the resulting TiO 2 film. In addition, the increased hydrophilicity of the TiO 2 film by the ion beam treatment led to an increase in dye adsorption. The oxygen ion beam treatment at 500 and 1000 eV caused a significant decrease in oxygen vacancies and increase in the open-circuit voltage (V oc ). Oxygen ion beam-treated TiO 2 film electrodes showed the maximum solar-to-electricity conversion efficiency (g%) of 8.04% compared to the 6.15% obtained from an untreated TiO 2 electrode.

Improved Nonaqueous Synthesis of TiO2 for Dye-Sensitized Solar Cells

“…Suboxides with reduced titanium oxidation states were apparent in several of the spectra, particularly near 454.6 and 462.7 eV so the spectra were deconvoluted to quantify the Ti 2 O 3 (457.3 and 462.7 eV) and TiO (454.6 and 460.2 eV) observed at lower binding energies. 36 Although the observed peak near 454.6 eV was intermediate between reported binding energies of TiO (455.0 eV) and Ti metal (454.1 eV), 37 this peak was attributed to TiO after considering the high temperature calcinations in air. The Ti oxidation state distribution was calculated for each sample and is shown in Table 2 and Figures atom %.…”

“…For all samples, the predominant peaks correspond to the Ti 4+ oxidation state of TiO 2 with peaks near 459.0 and 464.8 eV of binding energy. Suboxides with reduced titanium oxidation states were apparent in several of the spectra, particularly near 454.6 and 462.7 eV so the spectra were deconvoluted to quantify the Ti 2 O 3 (457.3 and 462.7 eV) and TiO (454.6 and 460.2 eV) observed at lower binding energies . Although the observed peak near 454.6 eV was intermediate between reported binding energies of TiO (455.0 eV) and Ti metal (454.1 eV), this peak was attributed to TiO after considering the high temperature calcinations in air.…”

“…Such a mechanism could explain the slightly less reduced character of the Ti in BA Nb:TiO 2 compared to BA TiO 2 after calcination. Although all crystalline lattices have some intrinsic thermal disorder with a specific equilibrium vacancy concentration, , the specific preparatory conditions can have lasting effects ,,, when there are slow kinetics for vacancy formation/elimination. The oxygen 1s spectra showed no significant differences between the samples except for the shoulder near 532–533 eV corresponding to hydroxyl groups, chemisorbed oxygen or adsorbed water (Figure b).…”

Development of Dye-Sensitized Solar Cells with Sputtered N-DopedTiO2Thin Films: From Modeling the Growth Mechanism of the Films to Fabrication of the Solar Cells

“…All spectra were decomposed in three characteristic contributions: Ti 2+ 2p 3/2 , Ti 3+ 2p 3/2, and Ti 4+ 2p 3/2 . These peaks are, respectively, assigned to TiO, Ti 2 O 3, and TiO 2 [34,35]. However, for titanium oxynitridelike structures, TiO cannot be clearly distinguished by XPS because the peak Ti 2+ 2p 3/2 is also assigned to TiN [25].…”

Surface modification and retardation of back reaction by nitrogen ion-beam treatment in dye-sensitized solar cells

“…Plasma and ion-beam techniques were considered to be effectual surface modification methods to tailor the physical and chemical properties of metal oxide surface. The oxygen ion-beam and plasma treatment were reported to enhance the DSSC performance [6,7]. Nitrogen plasma and ion-beam modified TiO 2 films were mostly applied to investigate the photooxidation, photocatalytic conversion and photoreduction in different applications [8,9].…”