Impact of B 2 H 6 plasma treatment on contact resistivity in silicon heterojunction solar cells

We investigated the effect of the B 2 H 6 plasma treatment on p-type hydrogenated amorphous silicon (p-a-Si:H) surfaces for high-performance silicon heterojunction (SHJ) solar cells. Secondary ion mass spectroscopy measurements revealed that the boron concentration at the p-a-Si:H surface is increased by employing the B 2 H 6 plasma treatment. Furthermore, specific contact resistance is decreased by about one-third after the B 2 H 6 plasma treatment. No degradation of passivation performance is induced by the B 2 H 6 plasma treatment. The power conversion efficiency of the SHJ solar cells with the B 2 H 6 plasma treatment is improved by the increase in fill factor (FF) due to decreased series resistance and increased shunt resistance. From numerical simulations, the upward band bending is enhanced at the heterointerface between transparent conductive oxide (TCO) and p-a-Si:H by the B 2 H 6 plasma treatment, which is responsible for the improved FF owing to facilitated tunneling holes from c-Si to p-a-Si:H layers and the TCO/p-a-Si:H heterointerface.