Hydrogen-rich c-Si interfacial modification to obtain efficient passivation for silicon heterojunction solar cell

How to passivate the heterojunction between the doped layer and the crystalline silicon (c-Si) base plays a crucial role for the silicon heterojunction (SHJ) solar cell to obtain high performance, especially high open-circuit voltage (V_OC) and fill factor (FF). Here, a hydrogen-rich c-Si interfacial modification was realized by preparing an ultrathin (~ 1.5 nm) intrinsic hydrogenated amorphous silicon (a-Si:H) onto the c-Si(n) interface with pure silane via plasma enhanced chemical vapor deposition (PECVD), prior to the deposition of a ~ 8 nm relatively compact a-Si:H(i) layer for the a-Si:H(p)/c-Si(n) heterojunction. The enhanced effective minority carrier lifetime (τ_eff) of the c-Si base and V_OC of the final solar cell indicated that such interfacial modification improved the heterojunction passivation efficiently by saturating the c-Si dangling bonds (DBs) via hydrogenation with the following deposition of the compact a-Si:H(i) layer that kept the c-Si interface out of direct contact with the doped layer. By altering the deposition pressure, the hydrogen content (C_H) in the ultrathin a-Si:H was adjusted regularly to fabricate a series of SHJ solar cells with the area of 244.45 cm². A maximal conversion efficiency up to 23.81% was achieved with V_OC of 742.9 mV, J_SC of 38.67 mA/cm² and FF of 82.99% when the ultrathin a-Si:H had a relatively high C_H of about 24–25%.