Atmospheric-pressure-plasma-jet sintered dual-scale porous TiO2 using an economically favorable NaCl solution

•Dual-scale porous TiO2 was prepared by screen-printing and APPJ-sintering.•A low-cost NaCl solution was added into the TiO2 nanoparticle pastes.•During APPJ sintering, NaCl crystals precipitated as molds for large cavities.•DI water rinsing dissolved NaCl to form large cavities in nanoporous TiO2.•DSSCs with dual-scale porous TiO2 photoanodes show improved performance.

We have developed a rapid atmospheric pressure plasma jet (APPJ) sintering process for nanoporous TiO2 containing large cavities (of the order of a few hundreds of nanometers to a few micrometers) using an economically favorable NaCl solution. Screen-printing was used to administer mixed pastes consisting of TiO2 nanoparticles and NaCl solutions, following which APPJ sintering was conducted. During APPJ-sintering, numerous NaCl crystals precipitated and their sizes (large cavity sizes after DI-water rinsing) increased with the NaCl concentration of the added solution. The dual-scale porous TiO2 was then used as the photoanode of a DSSC. With an 1-wt% NaCl solution added to the TiO2 pastes, the efficiency (photocurrent density) increased from 5.89% (11.68 mA/cm2) to 6.57% (12.75 mA/cm2). The efficiency and photocurrent density of DSSC decreased as the NaCl concentration exceeded 1 wt%. Large cavities could enhance light scattering and light trapping, thereby increasing the photocurrent (short-circuit current) and efficiency. The oversized cavity, in turn, reduced the surface area for dye-adsorption (and therefore, the dye-loading) as well as the effective photocurrent transport path, leading to the reduction in the photocurrent and efficiency.

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