High　thermoelectric　energy　conversion　efficiency　requires　a　large　figure-of-merit,　zT,　over　a　broad　temperature　range.　To　achieve　this,　we　optimize　the　carrier　concentrations　of　n-type　PbTe　from　room　up　to　hot-end　temperatures　by　co-doping　Bi　and　Ag.　Bi　is　an　efficient　n-type　dopant　in　PbTe,　often　leading　to　excessive　carrier　concentration　at　room　temperature.　As　revealed　by　density　functional　theory　calculations,　the　formation　of　Bi　and　Ag　defect　complexes　is　exploited　to　optimize　the　room　temperature　carrier　concentration.　At　elevated　temperatures,　we　demonstrate　the　dynamic　dissolution　of　Ag2Te　precipitates　in　PbTe　in　situ　by　heating　in　a　scanning　transmission　electron　microscope.　The　release　of　n-type　Ag　interstitials　with　increasing　temperature　fulfills　the　requirement　of　higher　carrier　concentrations　at　the　hot　end.　Moreover,　as　characterized　by　atom　probe　tomography,　Ag　atoms　aggregate　along　parallel　dislocation　arrays　to　form　Cottrell　atmospheres.　This　results　in　enhanced　phonon　scattering　and　leads　to　a　low　lattice　thermal　conductivity.　As　a　result　of　the　synergy　of　dynamic　doping　and　phonon　scattering　at　decorated　dislocations,　an　average　zT　of　1.0　is　achieved　in　n-type　Bi/Ag-codoped　PbTe　between　400　and　825　K.　Introducing　dopants　with　temperature-dependent　solubility　and　strong　interaction　with　dislocation　cores　enables　simultaneous　optimization　of　the　average　power　factor　and　thermal　conductivity,　providing　a　new　concept　to　exploit　in　the　field　of　thermoelectrics.　©　2022　Elsevier　Ltd