研究目的
To demonstrate a vacuum-free, room-temperature organic passivation of silicon with a superior passivation effect using a perfluorinated polymer 'Nafion' thin film, aiming for very low recombination of micro/nano-textured surface structures.
研究成果
The study demonstrates a vacuum-free, room-temperature organic passivation of silicon with a superior passivation effect, including a very high τeff of ~9.6 ms, iVoc of 724 mV, and low upper-limit SRV of 1.46 cm/s, using a perfluorinated polymer 'Nafion' thin film. The passivation effect originates from the sub-oxidization of Si surface dangling bonds by the organic Nafion molecule. This organic passivation scheme can compete with a-Si:H and Al2O3 thin films in the current PV field and has potential applications in Si PVs.
研究不足
The organic passivation scheme is hydrophobic but aerobic, requiring an O2 atmosphere for enhanced passivation effect. The passivation stability decreases when exposed to ambient environment with high relative humidity.
1:Experimental Design and Method Selection:
The Nafion thin films were spin-coated onto Si wafers using a precursor solution at 3500 rpm and subsequently annealed at RT-130 oC. The passivation effect was evaluated by measuring the effective minority carrier lifetime (τeff), implied open circuit voltage (iVoc), and surface recombination velocities (SRV).
2:Sample Selection and Data Sources:
n-type (100) and (111)-oriented float zone (FZ) Si wafers with double-side mirror-polished surfaces, a resistivity of 1-5 Ω·cm, and a thickness of 280 μm were used. Additionally, 180-μm-thick randomly textured n-type Czochralski (CZ)-grown wafers and micro/nanostructure textured n-type CZ-grown wafers were employed.
3:List of Experimental Equipment and Materials:
Spin-coating equipment, annealing oven, Sinton WCT-120 instrument for lifetime measurement, X-ray photoelectron spectroscopy (XPS) for chemical composition analysis, scanning electron microscopy (SEM) and atomic force microscopy (AFM) for surface morphology observation.
4:Experimental Procedures and Operational Workflow:
The Nafion thin films were fabricated by a simple spin-coating method without requiring a vacuum. The passivation effect was measured in various environments (O2/Ar/ambient) and relative humidity levels using a 'transparent glass box' with gas change switches.
5:Data Analysis Methods:
The lifetime curves of the maximum values of the samples were analyzed to understand the passivation mechanism. The chemical composition at the interface was analyzed by XPS.
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