Progress in Laser-Crystallized Thin-Film Polycrystalline Silicon Solar Cells: Intermediate Layers, Light Trapping, and Metallization

Abstract

Diode laser crystallization of thin silicon films on the glass has been used to form polycrystalline silicon layers for solar cells. Properties of an intermediate layer stack of sputtered SiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</sub> /SiN <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</sub> /SiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</sub> between the glass and the silicon have been improved by reactively sputtering the SiN <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</sub> layer, which result in enhanced optical and electrical performance. Light trapping is further enhanced by texturing the rear surface of the silicon prior to metallization. An initial efficiency of 11.7% with V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">OC</sub> of 585 mV has been achieved using this technique, which are the highest values reported for poly-Si solar cells on glass substrates. Cells suffer a short term, recoverable degradation of V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">OC</sub> , and fill factor. The magnitude of the degradation is reduced via the repeated thermal treatment. A selective p+ metallization scheme has been developed which eliminates the degradation altogether.