The importance of Se partial pressure in the laser annealing of CuInSe2 electrodeposited precursors

One method for producing CuInSe₂ (CISe) absorber layers is electrodeposition followed by annealing. Replacing the commonly used furnace annealing step with a laser can reduce annealing times by 2-3 orders of magnitude: from 30 minutes to 1 s. However, laser processing has, to date, not resulted in absorber layers which can form functioning final devices. One reason is due to Se loss during annealing even on these short timescales. We show how this Se loss is reduced by using a background partial pressure of Se (P_Se) during annealing. Higher P_Se results in increased grain size and drastically increased photoluminescence yield. The introduction of an elevated P_Se in the laser annealing chamber enabled the fabrication of the first known CuInSe₂ photovoltaic device using electrodeposition followed by laser annealing which gave 1.6% efficiency.