First hot-wire deposited triple junction silicon thin film solar cell

We present the first triple junction multibandgap cells incorporating three intrinsic absorber layers that are all deposited by hot wire CVD (Cat-CVD). The bottom and middle cell have a microcrystalline silicon (/spl mu/c-Si:H) absorber layer and the top cell has an amorphous silicon (a-Si:H) intrinsic layer. The cells are made in the configuration stainless steel/n-i-p/n-i-p/n-i-p/ITO and do not comprise a textured back reflector. We obtained a V/sub oc/ of 1.835 V, J/sub sc/ of 7.97 mA/cm/sup 2/, and a fill factor of 0.624. The open circuit voltage is appropriate for this structure, assuming a value of about 0.5 V for the two microcrystalline cells. The fill factor suggests that current matching is achieved, and the high J/sub sc/ shows that there is true spectrum splitting. The triple junction cell, with an efficiency of 9.1%, represents a considerable improvement over our previously presented HWCVD /spl mu/c-Si:H/a-Si:H tandem cells, which had an efficiency of 8.1%. No germanium has been used for this multibandgap cell. The elimination of germane and the use of HWCVD as a fast deposition technique make this triple junction cell concept very attractive for low cost, high efficiency thin film photovoltaic technology.