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a – 1,2,3,4,5,6 layers of an aligned MWNT; b – 6,7,8 layers of an aligned MWNT and Pt reference
Figure 5 – Current-voltage characteristics of DSCs with different combination of MWNT and Pt counter electrodes
Figure 6 – Dependence of the efficiency rate from number of layers
Different numbers of directly drawn aligned MWNT sheets were tested (1-8 layers) as CEs in DSCs and we achieved a high efficiency (6.95%) comparable to the
conventional Pt/FTO CE using 6 layers. Nanoscale edges on the MWNTs play an active role in fast dissociation of redox pairs and the sheet conductivity is critical in current collection. Conventional DSCs uses counter electrode with Pt catalytic particles coated on FTO films. The Pt particles is a well known material for a catalytic charge transfer between electrolyte and current collector. The relatively high obtained efficiency of DSCs (~ 6-7%) is determined by the high generated photocurrent, which is near to the reference DSCs made by same method using the standard Pt catalyst. The fill-factor of the device with combination of six layers MWNT is comparable with Pt reference (~0.7). Further improvement of electrochemical properties and conductivity of these carbon based electrodes is under investigation with MWNT sheets to achieve a higher performance device. One major concern, currently being studied, for the application of MWNT counter electrodes in DSC is long-term stability (Pt also suffers from instability in long term use). During prolonged exposure in a corrosive electrolyte, weakly adhered MWNTs may detach from the FTO glass substrate and get deposited on the TiO2 photoanode side, shorting out the cell. No evidence of this has been detected thus far with our cells.
This work was supported through the CONTACT program and the Welch Foundation AT-1617.
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Ключевые слова: форма, песок, смола, качество, моделирование, управление, газопроницаемость.
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