On the blistering of Al2O3 passivation layers for Si solar cells

Blister-free Al2O3-based surface passivation stacks for p-type Si passivated emitter and rear cells (PERCs) are developed. Measuring the blistering area and effective surface recombination velocity, it is shown that using (i) an Al2O3 layer ≤ 10 nm and (ii) out-gassing this Al2O3 film above 600 °C prior to capping is necessary. These blister-free Al2O3-based stacks are implemented as rear surface passivation for p-type Si PERC: 148.25 cm 2 screen-printed cells with an average efficiency of 19.0 % have been made. There is an obvious gain in open circuit voltage of 5 mV compared to SiOx passivated PERC, thanks to enhanced rear surface passivation.