Engineering an ideal intermediate-band photoelectric material based on diamond through defect engineering combined...

An ideal intermediate-band (IB) photoelectric material based on diamond (C₆₁B₂As) is designed theoretically through stress modulation. The results indicate that applying stress to the material can significantly reduce its total bandgap and sub-bandgap. The variation of the material's electronic structure exhibits directional dependence on stress, which should be due to the anisotropy of the material induced by doping. With the increase of uniaxial compressive stress, the sub-bandgap between the IB and the conduction-band (CB) of the configuration decreases dramatically, while the sub-bandgap between the valence-band (VB) and the IB shows relatively small variation. Under 120 GPa of uniaxial compressive stress, the electronic structure of the configuration meets the criteria for an ideal IB material. Under biaxial stress, the total bandgap, as well as the sub-bandgap between IB-CB and VB-IB, gradually decreases with increasing stress. When the biaxial stress increases to 120 GPa, the VB shifts upward and overlaps with the IB. Furthermore, the optical absorption spectra demonstrate that as the biaxial stress increases, the long-wavelength limit of optical absorption of the C₆₁B₂As configuration undergoes red-shift, with a significant enhancement of absorption in the infrared region. Calculations of the electron difference density within the supercell reveal that, upon applying pressure to the C₆₁B₂As configuration, atomic orbital overlap is enhanced, leading to the enhanced electron delocalization and reduction of the bandgap.