Physical criteria for the interface passivation layer in hydrogenated amorphous/crystalline silicon heterojunction solar cell

Abstract

AFORS-HET (automat for simulation of heterostructures) simulation was utilized to explore the physical criteria for the passivation layer in hydrogenated amorphous/crystalline silicon heterojunction (SHJ) solar cells, by systematically investigating the solar cell current density–voltage (J–V) performance as a function of the interface defect density (Dit) at the passivation layer/c-Si hetero-interface, the thickness (t) of the passivation layer, the bandgap (Eg) of the passivation layer, and the density of dangling bond states (Ddb)/band tail states (Dbt) in the band gap of the passivation layer. The corresponding impact regulations were presented clearly. Except for Dit, the impacts of Ddb, Dbt and Eg are strongly dependent on the passivation layer thickness t. While t is smaller than 4–5 nm, the solar cell performance is less sensitive to the variation of Ddb, Dbt and Eg. Low Dit at the a-Si:H/c-Si interface and small thickness t are the critical criteria for the passivation layer in such a case. However, if t has to be relatively larger, the microstructure, i.e. the material quality, including Ddb, Dbt and Eg, of the passivation layer should be controlled carefully. The mechanisms involved were analyzed and some applicable methods to prepare the passivation layer were proposed.