Operating limits of Al-alloyed high-low junctions for BSF solar cells

Abstract

Experimental estimations of the effective surface recombination velocity of the high-low junction (Seff) and of the base diffusion length are carried out for Al-alloyed n+pp+ bifacial cells and the results are presented in form of histograms. These results agree with calculated values of Seff when the characteristics of the recrystallized Si layer and heavy doping effects are taken into account. It is concluded that thick Al layers and high alloying temperatures (over 800°C) are necessary to obtain low values of Seff. This conclusion agrees with experimental results of other authors. Recomendations to avoid diffusion length degradation are given and the operating limits of the Al alloying technology are discussed. © 1981.