Mineralization of flexible mesoporous TiO₂ photoanodes using two low‐temperature dielectric barrier discharges in ambient air

Abstract

Two types of dielectric barrier discharges (DBDs), volume DBD (called Industrial Corona) and coplanar DBD, were used for low temperature (70 • C) atmospheric pressure plasma mineralization of mesoporous methyl-silica/titanium dioxide nanocomposite photoanodes. The photoanodes with a thickness of approx. 300 nm were inkjet-printed on flexible polyethylene terephthalate (PET) foils. Plasma treatments of both DBDs led to changes in the chemical stoichiometry and morphology of the mesoporous photoanodes, resulting in a significant increase of the work function from approx. 4.0 to 4.3 eV and 4.8 eV, after plasma mineralization with volume DBD and coplanar DBD, respectively. We also studied the effect of plasma mineralization on the photoelectrochemical properties of the flexible mesoporous TiO 2 photoanodes. Plasma mineralization with volume DBD and coplanar DBD showed different effects on the generated photocurrent in the photoanodes. Although the plasma mineralization with volume DBD showed only a minor effect on the photocurrent, plasma mineralization with coplanar DBD led to significantly higher photocurrents. We found that the enhancement of the photoelectrochemical properties was related to the homogeneity of the plasma-treated surfaces-arising from different spatial properties of the plasma between volume and coplanar DBDs. Furthermore, the results showed that plasma mineralization using coplanar DBD can effectively change the energy levels of the surface. This resulted in the enhancement of the work function and the photoelectrochemical properties of the mesoporous TiO 2 photoanodes. This contribution shows that coplanar arrangement of electrodes in DBDs generates plasma of higher efficacy compared with standard volume DBD that is currently often used in industrial processes. KEYWORDSdielectric barrier discharge (DBD), homogeneity of the treated surface, low-temperature plasma, mesoporous photoanodes, plasma mineralization INTRODUCTIONTitanium nanoparticles (TiO 2 NPs) are among the most widely used semiconductors in various applications such as water splitting, [1] photocatalysis, and energy-conversion processes. [2][3][4] TiO 2 NPs are in use as photoanodes in dye-synthesized solar cells (DSSCs), [5] and recently porous and/or compact TiO 2 layers are utilized in perovskite solar cells (PSCs).[6] TiO 2 NPs have been deposited using a variety of techniques, including deposition from vapour and liquid phases. [7][8][9] As the deposited NPs possess a large absorbing area, the TiO 2 layer is often contaminated by the adventitious organic impurities from the ambient

Perovskite Solar Cells with Low-Cost TiO2 Mesoporous Photoanodes Prepared by Rapid Low-Temperature (70 °C) Plasma Processing

“…61 Such increases in dielectric constant may well lead to higher capacity in the silica surface, manifesting as higher photocurrent, as measured in the coating in a previous study by the authors. 39 Furthermore, plasma treatment of m-TiO 2 shifts the valance and conduction band of the m-TiO 2 , 62 which may, in the case of the m-TiO 2 /perovskite interface, result in better band alignment of m-TiO 2 /perovskite. Consequently, this may also improve carrier injection from the perovskite layer into m-TiO 2 and enhance V OC .…”

Origin of the Catalytic Activity Improvement of Electrochemically Treated Carbon: An Electrical and Electrochemical Investigation

“…From Figure 4, it can be seen that the work function increases from 4.4 to 5.3 eV after electrochemical treatment. 34 The decrease in Fermi level energy indicates the change of n-type semiconductor behavior to p-type semiconductor (see the inset in Figure 4). The band gap of the materials is calculated from the UV spectrum (see Figure S9a,b).…”

Surface Property Tuning of Methylammonium Lead Iodide by Plasma for Use in Planar Perovskite Solar Cells

“…The temperature of the plasma unit during the treatment was approximately 60 °C. 33 , 34 Treatment times were 1, 2, 4, and 8 s, and samples were ordered in terms of “PVPT-treatment time”.…”