Technological steps reduction in the fabrication of high efficiency GaAs solar cells

A simplified method to make high-efficiency GaAs solar cells by isothermal liquid-phase epitaxy has been investigated. A graded GaAlAs window layer was grown by isothermal contact between a Be-doped GaAlAs melt and a n-type GaAs substrate. With the aim of further reducing the fabrication cost, attempts were made to grow the junction and the window on the as-cut side of the wafers; with small modifications in the cleaning process, efficiencies up to 20% were obtained. The following substrates were considered: polycrystalline, chemically/mechanically polished monocrystalline, and buffer layer. The best efficiency of 22.7% (under 24 suns AM1.5, 25 degrees C) was obtained when buffer-layer substrates were used.