Double-perovskite　halides　are　emerging　as　a　promising　class　of　materials　for　renewable　energy　solutions,　offering　expectation　in　the　search　to　address　the　global　energy　crisis.　With　their　unique　properties,　they　hold　the　potential　to　meet　the　key　challenges　in　sustainable　energy　production,　paving　the　way　for　a　cleaner,　more　efficient　future.　Consequently,　research　on　these　halides　may　have　applications　in　solar　cell　technologies.　This　study　examined　the　physical　properties　of　Cs2KAsA6　(A　=　Cl,　Br,　and　I)　double　perovskite　halides　via　DFT　calculations　grounded　in　the　FP-LAPW　method　for　potential　uses　in　renewable　energy　devices.　The　computed　Goldschmidt　tolerance　factor　and　formation　energy　indicate　that　the　investigated　halides　exhibit　structural　and　thermodynamic　stability　in　the　cubic　phase.　The　analysis　of　mechanical　characteristics　reveals　that　the　measured　Pugh　and　Poisson　ratios　indicate　ductility.　Furthermore,　we　employed　TB-mBJ　+　GGA　function　to　calculate　bandgaps.　We　explored　the　bandgap　properties　of　Cs2KAsCl6　(Eg　=　4.2　eV),　Cs2KAsBr6　(Eg　=　3.42　eV),　and　Cs2KAsI6　(Eg　=　2.75　eV)　direct　bandgap,　Becke-Johnson　(mBJ　+　GGA)　potentials　refining　the　bandgap　values　to　align　with　experimental　data.　Our　investigation　into　the　optical　characteristics　of　these　halides,　guided　by　their　complex　dielectric　functions,　reveals　that　they　exhibit　excellent　light　absorption　across　the　UV-visible　spectrum.　These　findings　highlight　the　materials＇　strong　potential　for　efficient　solar　cell　applications,　positioning　them　as　key　candidates　in　the　pursuit　of　advanced　renewable　energy　technologies.