Patent ID: 8637761
Filing Date: 2014-01-28
Classification: H01L,Y02E,Y02P

Abstract:
1. A method for fabricating a solar cell, the method comprising: purifying a metallurgical-grade (MG) Si feedstock using a directional solidification process; melting the purified MG-Si feedstock; lowering a single-crystal Si seed to touch the surface of the molten MG-Si; slowly pulling a single-crystal Si ingot out of the molten MG-Si; processing the Si ingot into wafers to form a plurality of MG-Si substrates for subsequent epitaxial growth, wherein a respective MG-Si substrate has a metal impurity level below 1e16/cm creating a plurality of pores on an upper surface of the MG-Si substrate to form a porous-Si layer, wherein the porous-Si layer has a porosity of less than 20%; leaching out residual metal impurities in the MG-Si substrate, wherein leaching out the residual metal impurities involves using HCl gas to react with the residual metal impurities; epitaxially growing a layer of single-crystal Si thin film doped with boron on top of the porous-Si layer; doping phosphorus into the single-crystal Si thin film to form an emitter layer; depositing an anti-reflection layer on top of the single-crystal Si thin film; and forming front and the back electrical contacts.