Lifetime studies on laser drilled vias for application in emitter-wrap-through-solar cells

Two laser sources potentially adequate for via drilling for the application in emitter or metallization wrap through cells are investigated. Both sources have the potential of very high throughput required for emitter wrap through cells. Three different drilling processes are analyzed and compared concerning the recombination activity of the resulting vias. Therefore the dependence of minority carrier lifetime on etching time in alkaline solution and via density is investigated. Further a method for determination of the surface recombination velocity originally derived for dislocations is applied to via holes. The calculated curves sufficiently describe the values derived from measurement, and values of S = 106 cm/s for the lowest etching times up to values of 100 cm/s for the highest etching times are deduced.