研究目的
To develop a novel approach for forming ultra-thin silicon oxide (SiOx) layers, known as passivated tunneling layers (PTLs), using CO2 plasma treatment of intrinsic hydrogenated amorphous silicon for the fabrication of passivated tunneling contacts in silicon heterojunction solar cells.
研究成果
The study successfully developed a new approach for obtaining PTLs via CO2 plasma treatment of an ultrathin a-Si:H(i) layer. The PTLs formed with higher treatment pressures exhibited oxygen-richer components and a smoother PTL/c-Si heterointerface, leading to a high implied open-circuit voltage of 743 mV and a low contact resistivity of around 60 mΩcm2. The in-situ process is suitable for forming PTLs in the rear-emitter heterojunction solar-cell configuration due to its high passivation quality and tunneling probability.
研究不足
The study focuses on the formation of PTLs using CO2 plasma treatment and their application in silicon heterojunction solar cells. The limitations include the specific conditions of the plasma treatment and the focus on n-type CZ Si wafers, which may not be directly applicable to other types of silicon wafers or solar cell configurations.
1：Experimental Design and Method Selection:
The study involved CO2 plasma treatment of intrinsic hydrogenated amorphous silicon to form PTLs. The treatment pressure was varied to investigate its effect on the formation of oxygen-richer components in the silicon oxide films.
2：Sample Selection and Data Sources:
One-side-polished n-type CZ Si wafers were used. The wafers underwent ultrasonic cleaning, RCA-1 and RCA-2 cleaning procedures, and hydrofluoric acid solution dipping to remove native oxides before a-Si:H(i) layer deposition.
3：List of Experimental Equipment and Materials:
Spectroscopic ellipsometry (SE, VASE?, J. A. Woollam), quasi-steady-state photoconductance (QSSPC) setup from Sinton Consulting (WCT-120), X-ray photoelectron spectroscopy (XPS) system with Cu Kα radiation, secondary-ion mass spectroscopy (SIMS, CAMECAIMS-7F-MAGNETIC-SECTOR), and high-resolution transmission electron microscopy (HR-TEM, JEM-2100F-HR-JEOL) were used.
4：Experimental Procedures and Operational Workflow:
After cleaning, 3-nm-thick a-Si:H(i) layers were deposited on both sides of the wafers, followed by in-situ CO2 plasma treatments with pressures ranging from 1600 to 2200 mTorr to form the PTLs. The thickness of the PTLs was determined using SE, and the minority carrier lifetime was measured using QSSPC.
5：Data Analysis Methods:
The contact resistivity was identified using the transfer length method (TLM). XPS was used to investigate the chemical composition of the PTLs, and SIMS was used to obtain depth profiles of various ion species at the PTL/c-Si heterointerface.
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