High efficiency silicon heterojunction solar cell using novel structure

Abstract

A novel approach for heterojunction silicon wafer solar cell fabrication is being investigated: This approach features nanocomposite plasma deposited amorphous silicon suboxides (a-SiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</sub> :H) for high-quality surface passivation combined with overlaying plasma deposited doped microcrystalline silicon (μc-Si:H(p+)/μc-Si:H(n+)) for use as heterojunction emitter and back-surface-field. Special attention is paid (i) to the front and back surface passivation of the wafer by high-quality wide-gap amorphous silicon suboxides (a-SiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</sub> :H), and (ii) to the influence of wide-gap high-quality μc-Si:H for use as emitter and back-surface-field (BSF). The p+ μc-Si:H films are likely to be suitable for use as emitter and BSF in a heterojunction solar cell device. They feature high transparency to suppress absorption, and high conductivity when annealed at the optimum temperature. Heterojunction solar cells fabricated by combining the excellent surface passivation properties of the intrinsic a-SiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</sub> :H and the doped highly-transparent μc-Si:H layers show a drastic increase of the open-circuit voltage (up to 702 mV for n-type substrates). These high open-circuit voltages can be consistently attributed to the excellent surface passivation by a-SiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</sub> :H preventing surface recombination at the hetero-interface.