OPTIMUM DESIGN AND PREPARATION OF A-SI/A-SI/A-SIGE TRIPLE-JUNCTION SOLAR-CELLS

A series of systematic studies have been made on both optimum design and preparation technology of high efficiency a-Si/a-Si/a-SiGe triple-junction solar cells. It has been found that current matching is one of the key factors affecting the fill factor of two-terminal tandem solar cells, and excess carrier recombination at the p-n interface acting as an internal electrode is dominated by the density of the minority carriers, interfacial states, and geometrical factor match of the materials at the p-n interface. In this work, mu c-Si:H With wide band gap and high conductivity, which was prepared at low substrate temperature, was used as an n layer of a-Si:H solar cells. In order to improve the n-i interface property, a novel approach involving the insertion of an n(-)a-Si:H buffer layer at the n-i interface was developed. The experimental results show that the buffer layer of appropriate thickness could enhance the till factor and open circuit voltage of a-Si:H based solar cells. In addition, highly photosensitive a-SiGe:H(F) films used for a bottom cell in a-Si/a-Si/a-SiGe triple junction solar cells have been obtained by glow discharge of a gas mixture (SiH4-GeF4-H-2) under conditions of high hydrogen dilution ratio and low deposition pressure. At present, the conversion efficiency of the a-Si/a-Si/a-SiGe triple-junction solar cell of 11.5% with V-oc=2.48 V, J(sc)=6.58 mA/cm(2), and FF=70.4% has been obtained under AM1(100 mW/cm(2)) illumination by optimization of the solar cell structure and preparation technology.