Contact control of Al/Si interface of Si solar cells by local contact opening method

Low-cost aluminum (Al) metallization process on p+ side of n-type silicon (Si) substrate with low recombination current density (J0met) is presented. Narrow-line Al screen-printed fingers on symmetrically passivated p+ -n-p+ Si precursors with local contact opening (LCO) are investigated. The Si content of the Al pastes, LCO patterns and Al finger widths are varied to evaluate the formation quality of the Al-doped p+ region. By increasing the pitch distance of the dot-shaped LCOs, the inverted pyramid cavities are found after removing the Al-Si eutectic part by HCl. The tendency of the reaction during the sintering process is controlled by fritting the Al paste with Si, which allows a faster Si saturation in the paste matrix and facilitates faster return of Si to the LCO region. With a combination of narrow-line fingers of 90 μm and a dot-shaped LCO pitch of 140 μm, J0met value of 420 fA/cm2 is realized.