2-Step Growth Method and Microcrystalline Silicon Thin Film Solar Cells Prepared by Hot Wire Cell Method

Abstract

Hot Wire Cell (HW-Cell) method has been developed in order to grow microcrystalline silicon (µc-Si:H) thin films. The influence of various deposition parameters on the structural and electrical properties of the films was investigated to improve film quality. It was found that the concentrations of O and C atoms in µc-Si:H films could be reduced from the order of 10²¹ cm^-3 to the order of 10²⁰ cm^-3 by decreasing the partial pressure of SiH₄ from 100 mTorr to 3 mTorr. Then, a novel 2-step growth method was proposed in order to reduce the incubation layer in the initial growth of µc-Si:H i-layer. By using this method, J _sc largely increased (10.11 → 18.32 mA/cm²), and as a result, the conversion efficiency of 3.9% could be achieved. The influence of the incubation layer on solar cell performances was also investigated by a numerical analysis. To date, a conversion efficiency of 5.3% (V _oc: 0.48 V, J _sc: 20.56 mA/cm², F.F.: 0.54, active area: 0.086 cm², AM1.5) was obtained for µc-Si:H solar cells with an i-layer thickness of 1.0 µm. Furthermore, high-rate depositions were investigated and a maximum deposition rate of 11.5 nm/s could be achieved. µc-Si:H solar cells fabricated at a high deposition rate of 1.5 nm/s showed a conversion efficiency of 2.8% (V _oc: 0.42 V, J _sc: 12.31 mA/cm², F.F.: 0.54, active area: 0.086 cm², AM1.5).