Optimisation of laser-fired aluminium emitters for high efficiency n-Type Si solar cells

In order to investigate the local laser-fired aluminium emitters (LFE), a process recently developed at Fraunhofer ISE, high-efficiency n+np+ back junction solar cells with resistivities of 1, 10 and 100 ohm cm were fabricated. The laser-induced damage was analysed and modelled using a two-dimensional DESSIS simulation. The injection-dependent Shockley-Read-Hall recombination in the direct vicinity of the local back-junction is believed to strongly influence the cell erformance and cause large cell performance differences for different resistivity cells. Optimisation of the distance of laser-fired emitter points was performed. The importance of the annealing step following laser processing is shown. Effective excess carrier lifetimes of the 100 ohm cm FZ n-type Si up to 18 ms are reported.