Oxide-based double perovskites are gaining increasing attention as stable and environmentally benign alternatives to halide perovskites in photovoltaic and optoelectronic devices. Their structural versatility and chemical flexibility open pathways for fine-tuning both electronic and lattice properties, yet their carrier dynamics and defect behavior remain less understood. In this work, we investigate these aspects using a combination of first-principles calculations and advanced simulation techniques. Nonadiabatic molecular dynamics is employed to capture ultrafast carrier relaxation and to quantify the role of electron–phonon coupling in determining charge transport and recombination lifetimes. The results highlight efficient charge separation and suppressed nonradiative recombination channels, which are essential for high photovoltaic efficiency. To establish the dynamical stability of the materials, we carry out a phonon-based symmetry analysis that confirms the absence of imaginary modes and reveals the interplay between structural distortions and vibrational spectra. In parallel, we explore the formation and dynamic evolution of intrinsic point defects through defect-mediated molecular dynamics simulations. These studies shed light on migration pathways, possible defect-assisted recombination channels, and their impact on overall carrier dynamics. The comparative analysis reveals how compositional variations influence defect tolerance, lattice anharmonicity, and the balance between radiative and nonradiative processes. Together, these insights provide a comprehensive understanding of the interplay between electronic excitations, lattice vibrations, and defect physics in oxide-based double perovskites. The findings point toward design strategies for engineering defect-resilient, dynamically stable photovoltaic absorbers with long carrier lifetimes, thereby advancing the development of robust next-generation solar materials
Manasa Basavarajappa