In our previous study we have demonstrated that nanoporous

In our previous study, we have demonstrated that nanoporous TiO2 can be sintered by APPJs in less than 1 min [21], [22] and [23]. Sintered nanoporous TiO2 can be applied to photoanodes of DSSCs; these DSSCs have ABT-378 conversion efficiencies comparable to those with photoanodes calcined for 15 min (excluding the ramping and cooling times) using a conventional furnace. The introduction of oxygen can further accelerate the APPJ sintering process and reduce the TiO2 sintering time to 30 s while lowering the temperature from ~500 to ~300 °C [22]. Most recently, we have successfully applied APPJs to sinter rGO counterelectrodes for DSSCs with a processing time of only 11 s. The required energy consumption is estimated to be less than one-third of that using a conventional furnace calcination process. This new methodology significantly reduces the required energy, cost, and time to benefit mass production [24]. This APPJ sintering process is a two-step process. Pastes that contain TiO2 nanoparticles (or graphenes) and chemical binders are screen-printed on the substrates; the printed materials are then transported under APPJs for the sintering processes. This procedure is scalable and can be applied to roll-to-roll processes in which screen-printing is frequently used for the second and follow-up layers owing to the alignment requirement. This sequential screen-printing and APPJ sintering process is considerably different from the plasma spray technique, which involves high temperature plasmas (~10,000-20,000 K) to melt and spray materials onto the workpiece [25] and [26]. It is also noted that spark plasma sintering (also known as field assisted sintering or pulsed electric current sintering) uses a pulse electric current to sinter the materials; in fact no plasmas are involved in the process [27], [28], [29] and [30].