Study of Migration Behavior and Optical Properties of Self‐Trapped Hole by Hydrogen Vacancy in KH2PO4 Crystal

The behavior of self‐trapped holes (STH) adjacent to a H vacancy in K (KDP) crystals is investigated using the DFT + U and hybrid density functional calculations. The calculated results reveal that STH is located on one O atom near and introduces new defect energy levels in the bandgap. The hole tends to be self‐trapped and is more stable at room temperature along with partial lattice distortions. The STH in KDP crystals has a large migration barrier energy, implying a small mobility rate. The optical properties associated with STH are calculated and the emission peak is predicted to be 2.55 eV (487 nm) and the absorption peak to be 4.58 eV (271 nm), which is in good agreement with the experimental results.