Shining a Hot Light on Emerging Photoabsorber Materials: The Power of Rapid Radiative Heating in Developing Oxide Thin-Film Photoelectrodes
Ronen Gottesman, Isabella Peracchi, Jason L. Gerke, Rowshanak Irani, Fatwa F. Abdi, Roel van de Krol
Abstract
The unique possibilities of rapid thermal processing (RTP) for overcoming two significant challenges in the development of oxide thin-film photoelectrodes are demonstrated. The first is the need to exceed normal temperature limits for glass-based F:SnO2 substrates (FTO, ∼550 °C) to achieve the desired density, crystallinity, and low defect concentrations in metal oxides. Flash-heating of Ta2O5, TiO2, and WO3 photoelectrodes to 850 °C is possible without damaging the FTO. RTP heating-rate dependencies suggest that the emission spectrum of the RTP lamp, which blue-shifts with increasing heating power, can significantly influence the crystallization behavior of wide-bandgap photoelectrodes (≥1.8 eV). The second challenge is avoiding the formation of structural defects, trap states, grain boundaries, and phase impurities, which can be particularly difficult in multinary metal oxides. RTP treatment of α-SnWO4, a promising photoanode material, resulted in an increase in grain size and favorable crystallographic reorientation, culminating in a new performance record.