TiO 2 Film Morphology, Electron Transport and Electron Lifetime in Ultra-fast Sintered Dye-sensitized Solar Cells
- PDF / 419,612 Bytes
- 6 Pages / 432 x 648 pts Page_size
- 72 Downloads / 174 Views
TiO2 Film Morphology, Electron Transport and Electron Lifetime in Ultra-fast Sintered Dye-sensitized Solar Cells Matthew J. Carnie1, Cecile Charbonneau1, Matthew Davies1, 2, Ian Mabbett1, Trystan Watson1, and David Worsley1* 1 SPECIFIC, College of Engineering, Swansea University, Baglan Bay Innovation and Knowledge Centre, Central Avenue, Baglan SA12 7AX. 2 School of Chemistry, Bangor University, Bangor, Gwynedd, UK
ABSTRACT With the application of near-infrared radiation (NIR), TiO2 films for dye-sensitized solar cells (DSCs) on metallic substrates can be sintered in just 12.5 s. The photovoltaic performance of devices made with NIR sintered films match those devices made with conventionally sintered films prepared by heating for 1800 s. Here we characterise the electron transport, electron lifetime and phase-morphological properties of ultrafast NIR sintered films, using impedance spectroscopy, transient photovoltage decay and x-ray diffraction measurements. An important factor in NIR processing of TiO2 films is the peak metal temperature (PMT) and we show that during the 12.5 second heat treatment that a PMT of around 635 °C gives near identical electron transport, electron lifetime and morphological properties, as well comparable photovoltaic performance to a conventionally sintered (500 °C, 30 mins) film. What is perhaps most interesting is that the rapid heating of the TiO2 (to temperatures of up to 785°C) does not lead to a large scale rutile phase transition. As such photovoltaic performance of resultant DSC devices is maintained even though the TiO2 has been at temperatures which traditionally would have reduced cell photocurrents via anatase-to-rutile phase transition. INTRODUCTION 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. These include binder removal from and sintering of the TiO2 paste precursor to form the working electrode (30 min at between 450 °C to 500 °C) [1, 2], TiCl4 treatment (~60 mins) [3] and platinisation of the counter electrode (400 °C, 30 mins) [4, 5]. To put this in perspective, if just one of these processes were carried out on a typical roll-to-roll coating line where line speeds of over 120 m min-1 are common, an oven would be required in excess of 3.6 km in length. Dyeing has traditionally taken up to 24 hours [5] but has recently been reduced to 5 minutes using a pumping procedure which also has the added benefit of appearing to increase the effectiveness of co-sensitization with resulting efficiencies greater than that of either dye individually [6]. In 2011 we reported a novel near-infra-red (NIR) heat treatment that could achieve TiO2 sintering upon metal substrates in just 12.5 seconds [7]. The application of NIR radiation has recently been demonstrated as a method for removing a number of other bottlenecks in the manufacture of dye-sensitized solar cells [8]. It has been shown that NIR can be used to significantly reduce the pr
Data Loading...
