Nanoporous Tin Oxides and Titanium Dioxide/Carbon Nanotube Composites Fabricated using Rapid Atmospheric-Pressure-Plasma-Jet Processes: Application to Dye-Sensitized Solar Cells
Date Issued
2015
Date
2015
Author(s)
Wang, Ching
Abstract
We used atmospheric pressure plasma jets (APPJs) for the rapid sintering of nanoporous SnO2 and CNT/TiO2. The latter was used as the counter-electrodes of dye-sensitized solar cells (DSSCs) to replace conventional precious Pt-based counter electrode. DSSCs fabricated using APPJs were compared with those made using conventional furnace calcination process. In the first part of the experiment, we sinter nanoporous tin oxide films using atmospheric pressure plasma jets (APPJs). Comparing to conventional furnace calcination process, APPJ sintering substantially reduces treatment time and thermal budget. With an increase in APPJ sintering time, the slope of optical absorption edge decreases and then increases, optical band gap decreases and then increases, the electrical conductivity increases and then decreases, and activation energy of electrical conductivity decreases and then increases. A proper APPJ sintering time is required for the sintered SnO2 to be used in certain application. The features of nanoporous SnO2 were defined by screening printing method, followed by APPJ sintering This sequential screening-printing and APPJ sintering process is applicable for roll-to-roll process. The high surface-to-volume ratio of nanoporous SnO2 make the synthesized materials useful for gas sensors or catalysts in some chemical reactions. The second part of the experiment is regarding the APPJ sintering process of CNT/TiO2 counter electrodes of DSSCs. When APPJ sintering time exceeds 15 s, the CNTs were mostly removed, indicating vigorous interaction between CNTs and N2 APPJ. In the samples sintered for the same durations by furnace-calcination process, plenty of CNTs were present This suggests that the vigorous reaction was caused by the synergetic effect of the N2 APPJ and the heat. DSSCs with CNT/TiO2 counter electrodes sintered for 5 s revealed best performance with a efficiency of 5.65%, a enhancement of 158% was achieved compared to 2.19% for the DSSC with as-deposited counter electrode. The efficiency approaches that of DSSC with sputtered Pt counter electrode. APPJ sintering reduces the fabrication thermal budget and processing time, thereby lowering the cost. The process can be scaled up as a roll-to-roll process.
Subjects
APPJ
SnO2
DSSC
CNT
Type
thesis
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