Insights into the stability of amorphous/crystalline silicon interface under light and temperature

With silicon heterojunction (SHJ) solar cells inching closer to their practical efficiency limit, long-term reliability, and stability are the key to improve their market adoption. The origins of passivation degradation over time under field operating conditions at the amorphous silicon (a-Si:H)/crystalline silicon (c-Si) interface remains unclear. Herein, we investigate the passivation quality of a-Si:H/c-Si by extracting surface recombination velocity (SRV) from temperature- and injection-dependent lifetime spectroscopy measurements and retrieving interface defect density and charge density at the interface. Our results show a-Si:H/c-Si interface passivation degrades over time due to increase in SRV originating from failing chemical passivation exhibited by an increase in defect density at the interface while field passivation remained the same. Moreover, microstructural analysis of a-Si:H/c-Si with Fourier transform infrared spectroscopy (FTIR) shows increase in defect density at the interface originates due to changes at the interface and not in the bulk of a-Si:H.