研究目的
Investigating the bulk photovoltaic effect in chiral crystals within the visible spectrum to identify materials with large photoconductivity for potential applications in solar energy conversion.
研究成果
The study theoretically predicted strong shift currents in chiral crystal materials, with three-dimensional photoconductivity ranging from ~20 to ~80 μA/V2, comparable to the largest reported values in insulators and semiconductors. It was found that SOC generally plays a negative role in the shift current. The findings suggest that chiral crystals can host both quantized CPGE and a strong shift current, offering a promising platform for studying the bulk photovoltaic effect and its applications in solar energy conversion.
研究不足
The study is limited by the accuracy of DFT calculations with generalized gradient approximations (GGAs), which may underestimate the band gap in insulators. Additionally, the negative role of spin-orbit coupling (SOC) on the shift current in most cases may limit the photoconductivity in materials with strong SOC.
1:Experimental Design and Method Selection:
The study utilized density functional theory (DFT) calculations to analyze the electronic band structures and photoconductivity of chiral crystal materials. A quadratic response theory in the clean limit was employed to calculate the photoconductivity.
2:Sample Selection and Data Sources:
The study focused on a class of compounds MXY (with M = Ni, Pd, Pt, Rh, and Ir; X = P, As, Sb, and Bi; Y = S, Se, and Te) with chiral crystal structures. The electronic band structures were obtained from ab initio DFT calculations.
3:List of Experimental Equipment and Materials:
The calculations were performed using the full-potential local-orbital (FPLO) minimum basis code and the Vienna Ab initio Simulation Package (VASP).
4:Experimental Procedures and Operational Workflow:
The photoconductivity was calculated by projecting the ab initio DFT Bloch wave function into atomic-orbital-like Wannier functions and constructing an effective tight-binding model Hamiltonian. A dense k grid of 480 × 480 × 480 was used for the integral.
5:Data Analysis Methods:
The photoconductivity was analyzed based on the second-order response theory, considering the effects of spin-orbit coupling (SOC) and using symmetry analysis to determine the shape of the photoconductivity tensor.
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