Impact of Al Passivation and Cosputter on the Structural Property of β-FeSi2 for Al-Doped β-FeSi2/n-Si(100) Based Solar Cells Application

The aluminum (Al) doped polycrystalline p-type beta-phase iron disilicide (p-beta-FeSi2) is grown by thermal diffusion of Al from Al-passivated n-type Si(100) surface into FeSi2 during crystallization of amorphous FeSi2 to form a p-type beta-FeSi2/n-Si(100) heterostructure solar cell. The structural and photovoltaic properties of p-type beta-FeSi2/n-type c-Si structures is then investigated in detail by using X-ray diffraction, Raman spectroscopy, transmission electron microscopy analysis, and electrical characterization. The results are compared with Al-doped p-beta-FeSi2 prepared by using cosputtering of Al and FeSi2 layers on Al-passivated n-Si(100) substrates. A significant improvement in the maximum open-circuit voltage (V-oc) from 120 to 320 mV is achieved upon the introduction of Al doping through cosputtering of Al and amorphous FeSi2 layer. The improvement in V-oc is attributed to better structural quality of Al doped FeSi2 film through Al doping and to the formation of high quality crystalline interface between Al doped beta-FeSi2 and n-type c-Si. The effects of Al-out diffusion on the performance of heterostructure solar cells have been investigated and discussed in detail.