Fig. 3: Microstructure and transport properties of polycrystalline Pb1.004S0.6Se0.4 + zCu samples.

a Atomic resolution STEM image with Cu-rich area along [100] zone axis and (b) amplifying image of Cu-rich area. c The formation energy calculation results for point defects in PbS as the function of Fermi energy (EF) under Pb-rich condition. d Carrier density n and carrier mobility μ of Pb1.004S0.6Se0.4 + zCu samples. Temperature dependence of (e) electrical conductivity σ, (f) Seebeck coefficient S, (g) power factor PF, (h) total thermal conductivity κtot and lattice thermal conductivity κlat, (i) ZT value of Pb1.004S0.6Se0.4 + zCu samples.