Inorganic　mixed-halogen　perovskites　exhibit　excellent　photovoltaic　properties　and　stability;　yet,　their　photoelectric　conversion　efficiency　is　limited　by　inherent　surface　defects.　In　this　work,　we　study　the　impact　of　defects　on　properties　of　CsPbI2Br　slabs　using　first-principles　calculations,　focusing　on　specific　defects　such　as　I　vacancy　(V-I),　I　interposition　(I-i),　and　I　substitution　by　Pb　(Pb-I).　Our　findings　reveal　that　these　defects　affect　the　geometric　and　optoelectronic　properties　as　well　as　dynamics　of　charge　carriers　of　slabs.　We　employ　two　theoretical　frameworks　(surface　hopping　and　Redfield　theory)　of　nonadiabatic　molecular　dynamics　simulations　to　comprehensively　study　relaxation　processes　and　obtain　consistent　results.　The　presence　of　V-I　reduces　carrier　lifetimes,　while　the　influence　of　Pb-I　on　carrier　lifetimes　is　negligible.　In　contrast,　I-i　defects　lead　to　prolonged　carrier　lifetimes.　These　insights　provide　valuable　guidance　for　the　rational　design　of　perovskite　photovoltaic　devices,　aiming　to　enhance　their　efficiency　and　stability.