Thermal stability of PECVD a-Si:H single and PECVD a-Si:H + PECVD a-SiOx:H double layers for silicon solar cell rear side passivation

Hydrogenated amorphous silicon layers have been proven to potentially provide excellent passivation for crystalline silicon surfaces but typically show a sensitivity of the passivation effect to the thermal treatment of the samples after the deposition. This paper discusses the impact of different thermal processes in the range of 400°C to 850°C and of 3 s to 120 min on the passivation properties and on the hydrogen content of samples passivated with single a-Si:H and double a-Si:H + a-SiOx:H layers. Furthermore, the hydrogen depth profile after deposition and thermal treatment at 400°C and 550°C was investigated by nuclear reaction analysis showing a hydrogen accumulation at the a-Si/c-Si interface for the high temperature. This is accompanied by a bubble formation at the interface at 700°C. Rehydrogenation of a-Si:H layers is performed and characterised by carrier lifetime and Si-H bond density analysis.