研究目的
Investigating the application of vertical graphene nano hills (VGNH) directly grown on silicon for solar cell applications, focusing on optimizing the thickness of VGNH, minimizing surface recombination, and enhancing built-in potential to achieve high photocurrent and conversion efficiency.
研究成果
The study successfully demonstrated the fabrication of VGNH/Si and VGNH/Al2O3/Si solar cells with a conversion efficiency of 10.97% achieved through co-doping with PEDOT:PSS and HNO3. The high transmittance and low resistance of VGNH, along with texturing and doping, significantly improved the device's photocurrent and efficiency. The research presents a scalable approach for graphene-based photovoltaic devices without the need for graphene transfer.
研究不足
The study is limited by the high recombination rates and low built-in potentials in VGNH/Si devices without an interfacial layer. The efficiency is also affected by the uncontrolled oxidation at the graphene-silicon interface. The series resistance and ideality factor indicate room for improvement in device performance.
1：Experimental Design and Method Selection
The study involves the fabrication of VGNH/Si Schottky junction solar cells with and without an interfacial layer of Al2O3. The growth of VGNH was performed using plasma-enhanced chemical vapor deposition (PECVD) without any metal catalyst. The photovoltaic performance was analyzed by measuring I-V curves under solar simulated light.
2：Sample Selection and Data Sources
n-type (<100> phosphorous doped) bare silicon substrates with a resistivity of 1-5 Ω.cm were used. The substrates were cleaned using standard RCA-1 and RCA-2 methods, and texturing was performed to reduce reflectivity.
3：List of Experimental Equipment and Materials
PECVD system for VGNH growth, ALD (atomic layer deposition) chamber for Al2O3 growth, FE-SEM (Hitachi SU 8010) for morphology observation, Raman spectroscopy (Renishaw in-Via, 514.5 nm wavelength), AFM (Nanofocus Ltd.) for thickness and work function measurement, KPFM for work function estimation, UV-VIS-NIR spectrometer (Cary 5000, Varian Inc) for transmittance and reflectance measurements, solar simulator (Newport) for photovoltaic performance measurement.
4：Experimental Procedures and Operational Workflow
The substrates were cleaned and textured before the growth of VGNH. Al2O3 was deposited as an interfacial layer using ALD. VGNH was grown using PECVD at 750°C under RF discharge plasma. Metal grid electrodes were deposited using an e-beam evaporator. The devices were doped with PEDOT:PSS and HNO3 to enhance performance.
5：Data Analysis Methods
The photovoltaic performance was analyzed by measuring I-V characteristics under light and dark conditions. The series resistance, ideality factor, and Schottky barrier height were calculated from the I-V data. Raman spectroscopy was used to analyze the structural disorder of VGNH.
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