Perovskite materials have garnered attention in photovoltaic technology due to their impressive power conversion efficiency and narrow band gap. Despite achieving an overall efficiency of 25% for perovskite-based devices, they are plagued by issues such as toxicity, cost, and low stability. Addressing these shortcomings has prompted significant interest in alkali metal-based halide double Perovskites with the chemical formula A2BB'X6 (where A is alkali metal, and B and B’ represent monovalent and trivalent metals and X = Cl, Br, or I). These materials exhibit notable environmental stability, eco-friendliness, and non-toxicity. This article provides a comprehensive review of the various aspects of these halide double perovskites, including their structural, electronic, and optical characteristics. Furthermore, it explores their potential applications in the realm of optoelectronic, photovoltaic, and solar cell technologies. This research endeavors to pave the way for the development of more sustainable and efficient photovoltaic devices, addressing the pressing challenges faced by traditional perovskite materials.