Impact of bilayer structures on the surface passivation quality of high-rate-sputtered hydrogenated amorphous silicon for silicon heterojunction solar cells

Crystalline silicon surface passivation effect of intrinsic hydrogenated amorphous silicon (i-a-Si:H) films deposited by radio-frequency facing target sputtering (RF-FTS) using a two-step deposition technique was investigated. In the two-step deposition technique, an i-a-Si:H layer was deposited at a high sputtering power condition after the deposition of i-a-Si:H at a low sputtering power condition. The two-step deposition technique drastically improved the passivation quality of i-a-Si:H compared with a conventional single-step deposition technique. Only 0.5-nm-thick i-a-Si:H deposited at a low sputtering power suppresses the initial sputtering damage to the crystalline silicon surface. A high average deposition rate of 14.1 nm/min was also achieved. A non-textured silicon heterojunction solar cell using an i-a-Si:H passivation layer deposited by the two-step method shows a conversion efficiency of 17.4% (V-oc = 0.679 V, J(sc) = 35.0 mA/cm(2), FF = 0.732).