Electrochemical and Optoelectronic Analysis of Charge Transport, Recombination and Electron Lifetime in Ultra-fast Sintered TiO_2 Films for Dye-Sensitized Solar Cells

摘要

A number of the processing steps in making a DSC device take place in the timescale from minutes to hours and these process bottlenecks need to be addressed in order to scale up DSC manufacture. One such bottleneck is the binder removal from and sintering of the TiO_2 paste precursor to form the working electrode. This typically involves a heating step of around 30 min at between 450°C to 500°C [1, 2]. To put this in perspective, if the TiO_2 film were to be applied to a metal substrate on a typical roll-to-roll coating process where line speeds of over 120 m min~(-1) are common, then an oven would be required in excess of 3.6 km in length for just one 30 minute process. A second process limitation is the 30 min heating of the counter electrode at 400 °C [3, 4] to decompose H_2PtCl_6 and platinise the ITO or FTO surface and render the surface suitable as an electro-catalyst for tri-iodide reduction. The final lengthy process is the traditional dyeing method which involves immersing the prepared photoanodes in the dye solution for up to 24 hours [4]. Faster dyeing has been achieved by Hinsch [5] and Sommeling [6] in which they achieved dyeing in 30-60 minutes and recent work has reduced the dyeing time to 5 minutes using a pumping procedure [7]. This not only decreases dyeing time but also has the added benefit of appearing to increase the effectiveness of co-sensitization with resulting efficiencies greater than that of either dye individually [8].