High quality multicrystalline silicon grown by multi-stage solidification control method

¹ Steel Research Laboratory, JFE Steel Corporation Mizushima, Kurashiki 712–8511, Japan
² Nanomaterials Laboratory, National Institute for Materials Science 1-2-1, Tsukuba 305–0047, Japan
³ State Key Laboratory of Silicon Materials, Zhejiang University, Hangzhou 310027, P.R. China

Corresponding author: SEKIGUCHI.Takashi@nims.go.jp

Received: 8 September 2003
Accepted: 18 December 2003
Published online: 15 July 2004

Abstract

We have developed a method for growing high quality multicrystalline silicon (mc-Si) ingots for high efficiency solar cells. Grain size of the mc-Si wafers was controlled by the multi-stage solidification method. Impurity concentrations in the mc-Si ingots were also reduced by several ways. The efficiency of mc-Si solar cells produced from such mc-Si wafers has reached 18.3% with a cell area of 25 cm². In this paper we have investigated this high quality mc-Si by means of electron-beam induced current (EBIC), transmission electron microscopy combined with energy-dispersive X-ray analysis (TEM-EDX), and secondary-ion mass-spectroscopy (SIMS). EBIC results revealed that grain boundaries in MUST mc-Si were electrically inactive at room temperature. No metal impurities were detected at these grain boundaries.