High-efficiency ultra-thin CIGSe solar cells: defect engineering and back-surface field design.

Area of Science:

• Materials Science
• Renewable Energy
• Semiconductor Physics

Background:

• Ultra-thin solar cells offer potential for reduced material usage and flexible applications.
• Copper Indium Gallium Selenide (CIGSe) based thin-film solar cells are a promising photovoltaic technology.
• Optimizing device parameters is crucial for achieving high efficiencies in CIGSe solar cells.

Purpose of the Study:

• To comprehensively simulate and optimize an ultra-thin CIGSe/CdS/i-ZnO/ITO solar cell using SCAPS-1D.
• To investigate the impact of acceptor doping density, interface and bulk defect densities, and electron affinity on device performance.
• To explore the effectiveness of different back surface field (BSF) layers for performance enhancement.

Main Methods:

• Utilized SCAPS-1D (Solar Cell Capacitance Simulator in 1 Dimension) for device simulation.
• Systematically varied key physical parameters including acceptor doping density (Na), interface defect density (Nit), bulk defect density (Nt), and electron affinity (χ).
• Investigated Copper(I) oxide (Cu2O) as a back surface field layer and analyzed capacitance-voltage (C-V) and Mott-Schottky characteristics.

Main Results:

• Increased acceptor doping density (Na) significantly improved open-circuit voltage (Voc), fill factor (FF), and efficiency.
• Elevated defect densities (Nit, Nt) led to substantial performance degradation due to increased recombination.
• A Cu2O back surface field layer resulted in the highest simulated efficiency of ~40.3%, with Voc = 0.817 V, Jsc = 30.03 mA cm⁻², and FF = 82.88%.

Conclusions:

• Defect control, optimal band alignment (χ ≈ 4.35 eV), and effective back surface field engineering are critical for high-performance ultra-thin CIGSe solar cells.
• The study provides practical guidelines for fabricating efficient CIGSe solar cells.
• Simulated results indicate a significant potential for achieving high efficiencies in next-generation thin-film solar technologies.