Carrier Concentration Guiding High‐Efficiency Thermoelectric Power Generation and Cooling in N‐Type PbSe Crystals

ABSTRACT Thermoelectric materials enable near‐room‐temperature solid‐state cooling and full‐temperature‐range power generation. However, performance optimization is strongly dependent on carrier concentration, and its close correlation with carrier mobility makes precise tailoring critical for different application scenarios. In this work, guided by the theoretical framework that treats carrier concentration as the dominant variable, versatile high thermoelectric performance has been achieved in n‐type PbSe crystals. At low carrier concentrations (∼2.9 × 10 18 cm −3 ), samples exhibit an ultrahigh carrier mobility of ∼2369 cm 2 V −1 s −1 , thus enabling an exceptional average ZT of ∼1.02 at 323–523 K. This allows for simultaneous power generation and cooling, achieving a power generation efficiency η of ∼6.1% under a temperature difference Δ T of 270 K, while an all‐PbSe‐based device achieves a maximum cooling Δ T max of ∼48.5 K. At ∼2.5 × 10 19 cm −3 , samples demonstrate an ultrahigh average power factor of ∼33.3 µW cm −1 K −2 at 323–773 K, projecting a maximum power output ∼56 mW and a η of ∼7.7% at Δ T = 470 K. Our study reveals the uniqueness of carrier concentration in optimizing thermoelectric performance across different temperature regimes, as well as its versatility in enabling applications in both high‐efficiency power generation and cooling.