Alumina Passivation Films Prepared by Wet Process for Silicon Solar Cells Using Aluminum Isopropoxide as a Sol-Gel Precursor

Abstract

We prepared alumina passivation films for p-type silicon substrates by sol-gel wet process mainly using aluminum isopropoxide (Al(O-i-Pr)₃) as a precursor material. The precursor solution was spin-coated onto p-type silicon substrates and then calcined for 1 hour in air. Minority carrier lifetime of the passivated wafers was evaluated for different calcination temperature conditions. We also compared the passivation quality of the alumina passivation films using different alumina precursor, aluminum acetylacetonate (Al(acac)₃). Obtained effective minority carrier lifetime indicated that the lifetime is strongly depends on the calcination temperature. The substrate calcined below 400^°C shows relatively short lifetime below 100 µsec. On the other hand, the substrate calcined around 500^°C to 600^°C indicates lifetime from 250 to 300 µsec. Calcination temperature dependence of the lifetime for the samples using Al(O-i-Pr)₃ precursors shows almost the same as that using Al(acac)₃.