The Use of Near Infra Red as a Rapid Heat Treatment Process in the Manufacture of Metal-based Dye-sensitized Solar Cells

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1211-R08-06

The Use of Near Infra Red as a Rapid Heat Treatment Process in the Manufacture of Metal-based Dye-sensitized Solar Cells Trystan Watson, Ian Mabbett, and David Worsley Sustainable Coatings Research Group, Materials Research Centre, Engineering School, Swansea University, Singleton Park, Swansea, SA2 8PP, UK. ([email protected]) ABSTRACT A near infrared heating method is presented which directly heats metal substrates to very high temperatures within seconds. The technique is used to heat 1mm thick titanium and stainless steel metal coupons onto which 1 cm2 commercial TiO2 pastes have been deposited within 12-25 seconds giving assembled dye sensitized solar cell efficiencies which are equivalent to cells prepared using a convection oven for 1800 seconds. The near infrared method is applicable to different paste thicknesses and paste types as well as different metal substrates. Near infrared sintering for the shortest time 12.5 seconds yielded cells with the highest efficiency compared to convection oven prepared samples. This ultrafast heating seems to drive off binder very effectively and lead to rapid sintering. Ultrafast sintering allows peak metal temperatures of 500-800 ºC to be achieved without the massive losses in cell efficiency observed with the conventional heat treatment at temperatures over 600 ◦C. INTRODUCTION Dye-sensitized solar cells (DSC) have been developed over recent years as a viable low cost alternative to conventional silicon solar cells1, 2. The titanium dioxide based photo-anode is usually deposited from a paste which contains an organic binder. The standard method for bringing about the removal of binder, creating inter-particle connection and introducing porosity is through burning off the organic component by placing the coated electrode into a convection oven at 450 – 500 ◦C for 30 minutes1, 3. Several alternative methods have been proposed which can bring about the necessary processing of the TiO2 in times of under 5 minutes and these include compression4, microwaves5 and laser6 treatment. Of current interest is the application of DSCs to metal substrates7-9 as this offers the potential benefits of cell flexibility and ease of scale-up for manufacturing by roll to roll processes giving rise to low cost building integrated photovoltaic materials. Roll to roll manufacturing is already widely used to make pre-finished coated metals for buildings and there are various new paint curing technologies that can replace convection ovens leading to lower energy and faster manufacturing routes. One such technique is Near Infrared (NIR) heating which delivers radiative curing to the metal substrate effectively heating the applied organic coating from the metal coating interface rather than from the air coating interface. NIR technology therefore holds potential promise in the sintering of TiO2 layers mounted on metals since it can drive off organic moieties from the metal surface of the photo-anode and in particular it can do this extremely rapidly. Here we demonstrate the effec