Interaction mechanism between hydrogen and boron during the Al–Si solvent refining with hydrogen assistance

Silicon purification with Al–Si solvent refining is a potential method to obtain solar grade silicon (SoG-Si). Hydrogen is a helpful element to enhance the removal of impurity boron during the Al–Si solvent refining. However, the interaction mechanism between hydrogen and boron is not very clear. In this paper, the ab initio calculation method, which is based on the density functional theory (DFT), was adopted to further understand the interaction behavior of hydrogen and boron. The structure properties, bonding energy, energy band structure and density of states (DOS) of BH2, BH3, B2H6, SiH4 and AlH3 were calculated and analyzed using the CASTEP module in Materials Studio. The results show that BH2 has the feature of semiconductor, while BH3, B2H6, SiH4 and AlH3 belong to insulator. Additionally, the order of binding energy for hydrides from large to small is B2H6, BH3, SiH4, BH2 and AlH3, indicating that B2H6 is the most stable compounds among the hydrides. The DOS and partial density of states (PDOS) analysis show that the valence band of B2H6 contains four parts, which are contributed by H-1s and B-2s states, H-1s, B-2s and B-2p states, H-1s and B-2p states, H-1s and B-2p states, respectively. To verify the calculation results, an experiment and a thermodynamic analysis were carried out, and both of them proved that the calculation results agree well with the experimental results.