Effect of Ruthenium Ions on Grain Boundaries in Gallium Arsenide Thin Film Photovoltaic Devices

Abstract

Chemisorption of ruthenium ions decreases both the rate of carrier recombination at grain boundaries and the surface recombination velocity on thin film, polycrystalline grown by chemical vapor deposition. Charge collection scanning electron microscopy reveals a pronounced improvement in charge collection at gold Schottky barriers following ruthenium treatment. After chemisorption of ruthenium ions, a solar to electrical conversion efficiency of 4.8% was reached in the liquid junction cell with semiconductor grains of 3–7 μm diameter. The ruthenium effect here is much more dramatic than that shown in single crystal substrates, increasing the power conversion efficiency by up to a factor of four over etched specimens.