Improved power conversion efficiency in radial junction thin film solar cells based on amorphous silicon germanium alloys

Abstract

Advanced material combining with novel 3D radial junction design is an attractive strategy to fabricate low-cost high-efficiency thin film solar cells. For improving the power conversion efficiency of traditional a-Si:H thin film solar cells, a conceptually new method incorporating Ge doping technology with 3D radial junction architecture is proposed here. By doping Ge with the optimal amount, the eternal quantum efficiency response of a-Si:Ge alloy thin film solar cell is greatly improved in the near-infrared wavelength. This enhanced spectrum response contributes to the improved power conversion efficiency according to the experimental results and theoretical simulations. On the other hand, by introducing the 3D radial junction architecture, both the excellent light trapping effect and the fast carrier separation contribute to the significantly improved short current density. With the optimal Ge doping amount, the radial junction a-Si:Ge alloy thin film solar cell achieves an open circuit voltage of 0.58 V, short current density of 20.14 mA/cm2, and fill factor of 53.7%, which contributes to the high power conversion efficiency up to 6.26%. From beginning to end, the fabrication temperature is lower than 400 °C and the whole fabrication process shows remarkable compatibility with current photovoltaic industry application. All above results suggest a potential route to the next generation of stable and highly efficient a-Si:H thin film solar cells.