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Structural, Electronic, and Optical Properties of Br-Substituted Halide Perovskite KGeBr3-xClx (x = 0, 1, 2, 3): A DFT Study

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Abstract:

Halide perovskites are promising candidates for optoelectronic applications due to their tunable band gaps and strong optical response. In this work, the structural, electronic, and optical properties of the lead-free mixed-halide series KGeBr3-xClx (x = 0–3) are systematically investigated using first-principles calculations based on density functional theory (DFT). Structural optimization reveals a progressive lattice contraction from 169.86 ų (x = 0) to 145.6 ų (x = 3), accompanied by negative formation energies (−1.527 to −1.556 eV per atom for intermediate compositions), confirming thermodynamic stability. Electronic band structure calculations show that all compounds are direct band-gap semiconductors at the R-point, with band gaps increasing monotonically from 0.57 eV (KGeBr₃) to 0.89 eV (KGeCl₃). The intermediate compositions exhibit band gaps of 0.70 eV (x = 1) and 0.80 eV (x = 2), demonstrating effective band-gap engineering through halogen substitution. Optical analysis reveals static dielectric constants ranging from 6.29 to 6.80 and refractive indices between 2.5 and 2.6. The absorption edge shifts from 0.7 eV to 0.8 eV for x = 1 and x = 2, respectively, while energy-loss maxima reach approximately 0.33 near 4.5 eV. These results establish KGeBr3-xClx as a tunable, environmentally friendly semiconductor platform suitable for infrared optoelectronic and photovoltaic devices

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Periodical:

Key Engineering Materials (Volume 1061)

Pages:

75-84

DOI:

https://doi.org/10.4028/p-M3i0mF

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Online since:

August 2026

Authors:

Hamza Bochaoui*, Mohamed El Bouabdellati

Keywords:

DFT, Halide Perovskites, Lead-Free Semiconductors, Optoelectronic Materials

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© 2026 Trans Tech Publications Ltd. All Rights Reserved

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