Abstract
In recent years, dye-sensitized solar cells (DSSCs) have aroused intensive interests due to their high efficiency, low cost, and simple fabrication procedure. Pt is still the effective catalytic material for a DSSC counter electrode to reduce voltage loss and speed up the reduction of triiodide (I3-) ions. In order to reduce the cost of DSSCs, great deals of alternatives have been proposed to replace noble Pt. Multi-wall carbon nanotube (MWCNT) is one of the promising alternatives due to its high specific surface area and rapid electron transfer nature. Until now, various approaches have been made to fabricate MWCNT-base counter electrode, such as screen printing, doctor-blade and chemical vapor deposition. Most of methods must need the requirement of high temperature treatment to remove binder from the paste after the coating. The use of heat treatment limits the application in plastic substrates, and thus a low temperature method to fabricate the MWCNT-base film is needed for flexible DSSCs.In this study, electrophoretic deposition (EPD) was employed to make MWCNT-base counter electrode for DSSC. Firstly, an acid mixture solution was used to functionalize MWCNTs. According to the Raman spectra and SEM results, the defects and open-ends were observed by chemical functionalization. In general, those defects and open-ends would become catalytic sites and benefit the enhancement in the catalytic ability of MWCNTs. Consequently, it can be observed that the catalytic ability of MWCNT-base electrode and the efficiency of DSSC assembled with MWCNT-base counter electrode were much improved by the optimization of surface functionalization on the MWCNT. In addition, the CV test demonstrated that an excellent electrochemical stability of the prepared MWCNT counter electrode can be obtained. Comparing with tape-cast, the CNT electrode fabricated by EPD had better adhesion and catalytic ability because the binder added into the paste for coating CNT film by doctor blade which may produce some shielding effect on CNT and lower its catalytic ability. Therefore, the MWCNT electrode prepared by EPD could be great potential for use in low-cost DSSCs.