Raster Scanning Laser and UV Processing of nanocrystalline TiO 2 Films for Sintering in Dye Solar Cells: Device Performa
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Raster Scanning Laser and UV Processing of nanocrystalline TiO2 Films for Sintering in Dye Solar Cells: Device Performance, Throughput and Embodied Energy Girolamo Mincuzzi1, Valerio Zardetto1, Luigi Vesce1, Malte Schulz-Ruhtenberg2, Arnold Gillner2, Andrea Reale1, Aldo Di Carlo1, Thomas M. Brown1 1
CHOSE - Centre for Hybrid and Organic Solar Energy, Department of Electronic Engineering University of Rome Tor Vergata, Via del Politecnico 1, 00133 Rome (Italy) 2
Fraunhofer Institut fur Lasertechnik, Steinbachstrasse 15, Aachen, 52074 - Germany
ABSTRACT A crucial step in Dye Solar Cell (DSC) fabrication is the sintering of the TiO2 layer which needs to guarantee good electromechanical bonding between nanoparticles whilst maintaining sufficiently large porosity to yield performing devices. The standard procedure for TiO2 sintering requires firing in an oven at 500°C. An alternative procedure consists in utilizing laser scanning processing which has the advantageous potential of being noncontact, local, low cost, rapid, selective, automated and scalable. We analyzed and optimised a laser process for the sintering of the TiO2 layers in dye solar cells analyzing temperature profiles, throughput and the embodied energy. The development of electronic and photovoltaic devices on plastic substrates is of considerable interest due to the advantages they bring in terms of flexibility and easy processing for lightweight, low-cost large-area applications. An alternative sintering procedure compatible with flexible substrates and large area processing consists in utilizing a UV lamp. We subjected TiO2 pastes deposited on conductive transparent substrates to UV irradiation. Fully plastic devices fabricated through this method showed efficiencies of 4%. INTRODUCTION Dye Solar Cells (DSCs) are a low cost photovoltaic technology based on a sensitized nanoporous titania layer immersed in an electrolyte 1. Development of the technology over large areas requires both the optimization of module layouts and architectures [2,3] and the development of effective manufacturing processes. One of the crucial processing steps is that of the sintering of the TiO2 layer which needs to achieve the right electromechanical bonding between the titania nanoparticles and sufficient porosity. The standard procedure for TiO2 sintering requires firing in an oven at 450-500°C. Alternative methods consist in laser, pressure, microwave irradiation or infrared lamps [4]-[7]. Laser processing is particularly attractive because it is a highly automated, selective and a local process and has been applied for the sintering the TiO2 layer in DSCs [4,8-11]. We show that laser sintering can achieve the same performance as that of the conventional oven, showing also that the embodied energy of the laser process is competitive[4,10,11]. The development of electronic and photovoltaic devices on plastic substrates[12] is of considerable interest due to the advantages they bring in terms of flexibility and easy processing for lightweight, low-cost large-area application
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