A study of TiO₂ binder-free paste prepared for low temperature dye-sensitized solar cells

Abstract

A binder-free titania paste was prepared by chemical modification of an acidic TiO2 sol with ammonia. By varying the ammonia concentration, the viscosity of the acidic TiO2 suspension increased, thereby allowing uniform films to be cast. The photoelectrochemical performance of TiO2 electrodes, cast as single layers, was dependent on the thermal treatment cycle. Fourier transform infrared spectroscopy was used to characterize the extent of residual organics and found that acetates from the TiO2 precursor preparation were retained within the electrode structure after thermal treatment at 150 °C. Electrodes of nominal thickness 4 lm produced an energy conversion efficiency as high as 5.4% using this simple thermal treatment. A binder-free titania paste was prepared by chemical modification of an acidic TiO 2 sol with ammonia. By varying the ammonia concentration, the viscosity of the acidic TiO 2 suspension increased, thereby allowing uniform films to be cast. The photoelectrochemical performance of TiO 2 electrodes, cast as single layers, was dependent on the thermal treatment cycle. Fourier transform infrared spectroscopy was used to characterize the extent of residual organics and found that acetates from the TiO 2 precursor preparation were retained within the electrode structure after thermal treatment at 150°C. Electrodes of nominal thickness 4 lm produced an energy conversion efficiency as high as 5.4% using this simple thermal treatment.

A versatile binder-free TiO2 paste for dye-sensitized solar cells

“…TiO 2 pastes were formulated with the addition of a heterocyclic base to the starting acidic TiO 2 colloid and processed according to our previous study. 24 Briey, the base reacts with residual acetic acid groups and forms a salt. An increase in ion concentration between the acid À /base + couple promotes a decrease of the double layer repulsion between TiO 2 nanoparticles thereby contributing to occulation, which results in the formation of a viscous slurry.…”

“…Surface mediated CH 3 COO À /NH 4 + couples are formed within the slurry, which results in the reduction of the double layer repulsion between the particles; as a result this induces TiO 2 particles to occulate sufficiently to allow uniform lms to be cast. In our previous study, 24 the inuence of acetate molar ratio within the acidic TiO 2 colloid was investigated in low temperature processing of electrodes in DSSC. Lowering the molar ratio of TiO 2 to CH 3 COOH in the starting colloid and the amount of ammonia in the paste formation, followed by low temperature processing at 150 C for 15 minutes, resulted in the energy conversion efficiency of the DSSC increasing from 2.83 to 5.00% in comparison to Park's results.…”

“…In our previous study, 24 the inuence of acetate molar ratio within the acidic TiO 2 colloid was investigated in low temperature processing of electrodes in DSSC. Lowering the molar ratio of TiO 2 to CH 3 COOH in the starting colloid and the amount of ammonia in the paste formation, followed by low temperature processing at 150 C for 15 minutes, resulted in the energy conversion efficiency of the DSSC increasing from 2.83 to 5.00% in comparison to Park's results.…”

Reduction of crack formation in TiO 2 mesoporous films prepared from binder-free nanoparticle pastes via incorporation of electrospun SiO 2 or TiO 2 nanofibers for dye-sensitized solar cells

“…All of these would deteriorate the properties of TiO 2 mesoporous film and thus reduce the device performance. Hence, it is important to develop innovative method to prepare TiO 2 film with superior film integrity/quality from binder-free paste of TiO 2 nanoparticles [7].…”

Solution processable titanium dioxide precursor and nanoparticulated ink: Application in Dye Sensitized Solar Cells

“…Hence, the use of water and/or ethanol user-friendly solvents to the formulation of TiO2 inks is desirable. Other volatile additives applied in low quantity, such as HCl or NH3, can also be added; but organic compounds with high boiling points, frequently used as additives to control the viscosity of the paste and the porosity of the resulting film, must be avoided [14,15]. On the other hand, the intimate contact between nanoparticles is mandatory to reach a good electron transport, but it is hard to achieve in processes performed at low temperature.…”