Showing papers on "Photoelectrolysis published in 2000"

Efficient Solar Water Splitting, Exemplified by RuO2-Catalyzed AlGaAs/Si Photoelectrolysis

Abstract: Contemporary models are shown to significantly underestimate the attainable efficiency of solar energy conversion to water splitting, and experimentally a cell containing illuminated AlGaAs/Si RuO2/Ptblack is demonstrated to evolve H2 and O2 at record solar driven water electrolysis efficiency. Under illumination, bipolar configured Al0.15Ga0.85As (Eg = 1.6 eV) and Si (Eg = 1.1 eV) semiconductors generate open circuit and maximum power photopotentials of 1.30 and 1.57 V, well suited to the water electrolysis thermodynamic potential: H2O → H2 + 1/2O2; E°H2O = EO2 − EH2; E°H2O(25 °C) = 1.229 V. The E°H2O/photopotential matched semiconductors are combined with effective water electrolysis O2 or H2 electrocatalysts, RuO2 or Ptblack. The resultant solar photoelectrolysis cell drives sustained water splitting at 18.3% conversion efficiencies. Alternate dual band gap systems are calculated to be capable of attaining over 30% solar photoelectrolysis conversion efficiency.

Selective heteroepitaxy of InGaP/GaAs/silicon devices as low-cost photovoltaic/photoelectrolysis cells for generating hydrogen from sunlight

Abstract: InGaP/GaAs photovoltaic-photoelectrochemical (PV-PEC) cells made by MOCVD on GaAs substrates have demonstrated high conversion efficiencies for the direct generation of hydrogen from sunlight and water. The present work is an experimental effort to develop and assess potential low-cost alternative fabrication technologies for such PV-PEC cells. Our strategy is to utilize a cheap silicon substrate and simple epitaxial growth techniques. Since PV-PEC cells do not require a semiconductor p-n junction nor front metallization, a mesa-array device structure is proposed that can be made by selective epitaxy. Selective epitaxy of small-area (10 to 100 microns on a side) mesas should yield significant stress and defect reduction. We describe the fabrication of such cells with GaAs-on-silicon heteroepitaxy by a close-spaced vapor transport (CSVT) technique in combination with selective InGaP liquid-phase epitaxy (LPE).