KNU Physics Thesis Presentations
# A cost-effective hybrid density functional theory calculation: cesium lead halide perovskite alloys and point defects in diamond Si

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Asia/Seoul

102호 (219동)
### 102호

#### 219동

Description

Many physical properties of materials should be thoroughly investigated to make efficient semiconductor devices. Density functional theory (DFT), which is a computational quantum mechanical modeling method, has been widely used to analyze the material properties of semiconductor materials. Hybrid DFT has recently been preferable as a means to correctly obtain the physical properties of materials more than the generalized gradient approximation (GGA). But its high

-throughput calculations bring about a high computation cost. To lower the cost, we downsampled the k-point grid for Hartree Fock (HF) exchange in hybrid DFT. As a result, the computation cost was reduced by about several ten times without losing much accuracy.

We applied this approach to two systems. Firstly, the stability and electronic band gap of Cs8Pb8I24(1-x)Br24x and Cs8Pb8Br24(1-x)Cl24x, well-known for hybrid organic-inorganic perovskites (HOIP), were investigated. The perovskite alloys of the orthorhombic phase are stable at room temperature (300 K) due to mixing entropy. The electronic band gap calculated by the hybrid DFT was in better agreement with the experimental band gap than that calculated by the GGA. Secondly, the stability of point defects in diamond silicon was investigated. The defect formation energy and charge transition levels of P dopant, Si self-interstitials, and vacancy defects were calculated in consideration of the charge state of defects.

지도교수: 도중회/박지상