研究目的
To investigate the use of Na2S as a new alkaline source for post-deposition treatment (PDT) in CIGS solar cells to enhance efficiency by passivating the surface and controlling point defects.
研究成果
Na2S PDT effectively enhances CIGS solar cell efficiency to 19.2% by reducing surface recombination through passivation of point defects like VCu and InCu, outperforming NaF PDT. This provides a valuable guideline for developing high-efficiency CIGS cells, particularly for mass production focusing on Na-only processes, with potential for further improvements in Jsc and overall performance.
研究不足
The study is limited to laboratory-scale CIGS solar cells with specific deposition and treatment conditions; scalability to industrial production may require further optimization. The use of toxic materials like KCN and CdS poses environmental and health concerns. The analysis did not detect sulfur after annealing, limiting understanding of its role, and the shallow Na diffusion depth might not be fully optimized for all applications.
1：Experimental Design and Method Selection:
The study employed a three-stage co-evaporation process for CIGS film deposition, followed by Na2S PDT involving evaporation and Se annealing. Characterization methods included SEM, XPS, SIMS, LTPL, and photovoltaic measurements to analyze surface morphology, chemical composition, defect states, and cell performance.
2：Sample Selection and Data Sources:
CIGS films were deposited on Mo-coated soda-lime glass substrates with a target composition of Cu0.85(In0.7Ga0.3)Se2. Samples were treated with Na2S PDT at various temperatures and annealing times, with reference samples without PDT or with NaF PDT.
3：85(In7Ga3)SeSamples were treated with Na2S PDT at various temperatures and annealing times, with reference samples without PDT or with NaF PDT.
List of Experimental Equipment and Materials:
3. List of Experimental Equipment and Materials: Equipment included a vacuum evaporator for deposition, SEM (Nova 230 by FEI Company), XPS (Thermo Fisher VG Scientific K-alpha), SIMS (TOF-SIMS5 by ION-TOF GmbH), LTPL system (LabRAM HR UV/vis/NIR PL), solar simulator (K3000 by McScience), EQE system (QEX10 by PV Measurement Inc.), and source measure unit (Keithley 236 by Keithley Instruments). Materials included Cu, In, Ga, Se, Na2S, KCN solution, CdS, ZnO, Al, and MgF
4：Experimental Procedures and Operational Workflow:
CIGS films were deposited via co-evaporation, treated with KCN, subjected to Na2S evaporation and Se annealing at specified temperatures and times, then fabricated into solar cells with CdS buffer, ZnO layers, and Al electrodes. Characterization involved SEM for morphology, XPS and SIMS for depth profiling, LTPL for defect analysis, and J-V and EQE measurements for photovoltaic performance.
5：Data Analysis Methods:
Data were analyzed using software like Avantage for XPS, with linear extrapolation for valence band edges, and standard methods for calculating photovoltaic parameters from J-V curves and EQE data.
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