The structural, electronic, optical, and thermoelectric properties of the Ge-based lead-free halide perovskite NaGeI3 have been investigated under various hydrostatic pressures ranging from 0 to 4 GPa utilizing the self-consistent Full-Potential Linearized Augmented Plane-Wave (FP-LAPW) method based on density functional theory (DFT), as implemented in the WIEN2k package. According to the structural investigation, the optimized lattice constant for NaGeI3 at 0 GPa is 5.91 Å, which reduces with applied pressure. Additionally, the studied perovskites have a direct bandgap of about 0.49 eV, indicating semiconducting behavior at ambient pressure. The bandgap decreases with an incremental application of pressure. Moreover, the optical functions improve under pressure, suggesting that these materials could be used in various optoelectronic devices operating in the visible and ultraviolet spectrums. The thermoelectric properties of the compound are explained in terms of electrical conductivity, thermal conductivity, Seebeck coefficient, figure of merit, and power factor. The study unveils promising properties of NaGeI3 under different pressures, opening new avenues for its application in optoelectronic devices.

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