Vacancy regulation to achieve N-type high thermoelectric performance PbSe through titanium-incorporation

Most high-performance thermoelectric materials, such as Bi₂Te₃, PbTe, and SnTe, rely on the costly and scarce element like tellurium, limiting their practical use. Recently PbSe has emerged as a promising candidate, showing high peak figure of merit (ZT) values at 900 K. However, PbSe is intrinsically p-type due to the lower formation energy of Pb vacancies, undermining the development of its n-type variants. This study reveals that incorporating titanium into PbSe can reverse the material to n-type and further enhance its thermoelectric performance. The electron localization function diagram and band structure calculations corroborate the P to N type transitions in Pb_0.996Se-y%Ti samples. Using a straightforward synthesis method, we examined various stoichiometric ratios of Pb_0.996Se-y%Ti (y = 1, 3, 5, 7, 10). Results show that n-type characteristics appear with titanium content above 3 %, linked to the formation of a secondary phase, TiSe. The highest ZT of 0.64 is achieved for Pb_0.996Se-5%Ti at 573 K, with an average ZT of 0.47 from 300 K to 500 K, and high power factor of 28.6 μW K⁻² cm⁻¹ is reached at 300 K, indicating the potential of Ti-incorporated PbSe for energy conversion applications at near room temperatures.