研究目的
To understand the effect of carbon on the photovoltaic properties of Cu2ZnSnS4 (CZTS) using first-principles density functional theory (DFT) based on the generalized gradient approximation (GGA).
研究成果
The presence of carbon in the CZTS material can reduce the transport efficiency if located in the S and Sn sites, respectively. An increase in the transport and photogeneration efficiencies is reported if the carbon is located at the zinc site, which forms the most stable site for C atoms. A reduction of thickness around 0.5 μm is suggested after doping CZTS with carbon.
研究不足
The study is limited by the use of GGA based DFT, which underestimates the band gap compared to experimental values. The theoretical values of band gap are lower than the experimental one (1.5eV), which could be attributed to the limitation of GGA based DFT.
1：Experimental Design and Method Selection:
The study uses first-principles density functional theory (DFT) based on the generalized gradient approximation (GGA) to investigate the crystalline structure, formation energy, electronic, optical, and current-voltage properties of CZTS with carbon impurity at various sites.
2：Sample Selection and Data Sources:
The study considers four substitutional configurations of carbon doped CZTS supercells: Cu by C (Ccu), Cu by Zn (Czn), Sn by C (Csn), and S by C (CS).
3：List of Experimental Equipment and Materials:
The QUANTUM ESPRESSO (QE) package is used for DFT calculations. Ultrasoft pseudo potentials for all atomic species are employed.
4：Experimental Procedures and Operational Workflow:
The electronic structure, density of states (DOS), and optical properties are computed based on optimized crystal structures. A 4 × 4 × 4 Monkhorst-Pack grid is used for k-point sampling.
5：Data Analysis Methods:
The dielectric function is calculated using the generalized Drude-Lorentz expression for the macroscopic complex dielectric. The absorption coefficient and reflectivity are calculated using derived equations.
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