To overcome the problem, a research group at the National University of Singapore has recently developed a gel-coating method for preparing CNT films on various substrates. The CNT gels, also called bucky gels, are formed by dispersing CNTs in a liquid nonionic surfactant, such as polyoxyethylene(12) tridecyl ether or low-molecular weight polyethylene glycol, via mechanical grinding or ultrasonication. The gels can be coated onto substrates using a surgical blade. The nonionic surfactant, which disperses the CNTs, can be removed by heating at a temperature below the decomposition temperature of CNTs. As a result, the gel-coated CNT films are free of binder. The CNT films have good adhesion to substrates and do not detach from the substrates when in water or organic electrolytes over a long period.

Long-term stability

As shown in the study, the binder-free CNT films fabricated by gel coating provide excellent electrochemical catalysis and can effectively catalyse the redox of iodide and triiodide. Devices featuring a gel-coated binder-free single-walled CNT (SWCNT) or multi-walled CNT (MWCNT) film as the counter electrode exhibit a photovoltaic efficiency comparable with the control DSCs based on a conventional Pt counter electrode. Moreover, the DSCs with the SWCNT counter electrode have better stability than the control DSCs.

The researchers presented their work in the journal Nanotechnology.