Achieving　high-stability　thermoelectric　materials　with　excellent　average　power　factor　and　figure　of　merit　is　crucial　for　maximizing　the　output　power　density　and　conversion　efficiency　of　thermoelectric　devices.　In　this　study,　GaSb　is　added　to　PbSe　as　an　n-type　dopant　to　form　stable　solid　solutions.　Doping　with　GaSb　flattens　the　conduction　band　and　reduces　the　energy　difference　between　the　Sigma　and　L　conduction　bands,　thereby　significantly　improving　the　Seebeck　coefficient.　Herein,　the　Ga　and　Sb　atoms　co-occupy　the　vacant　Pb　sites,　unlike　in　the　case　of　traditional　single-element　doping,　as　is　verified　by　density　functional　theory　calculations.　The　resultant　structural　distortion　is　confirmed　via　transmission　electron　microscopy.　This　local　structure　distortion　caused　by　GaSb　doping　reduces　the　lattice　thermal　conductivity.　Consequently,　the　Pb-0.99875(GaSb)(0.00125)Se　sample　exhibits　a　record-high　average　power　factor　of　similar　to　22.37　mu　W　cm(-1)　K-2　and　a　high　average　figure　of　merit　of　similar　to　0.94　in　the　temperature　range　of　300-873　K.　Furthermore,　the　introduction　of　interstitial　Cu　and　discordant　Zn　atoms　further　reduces　the　lattice　thermal　conductivity.　The　Pb-0.99875(GaSb)(0.00125)Zn0.01Se1.01-0.3%Cu　sample　exhibits　a　low　lattice　thermal　conductivity　of　similar　to　0.4　W　m(-1)　K-1　at　873　K　and　a　record-high　average　figure　of　merit　of　similar　to　1.01　in　the　temperature　range　of　300-873　K.