Enhancing the thermoelectric performance of n-type polycrystalline SnSe remains challenging due to the trade-off between carrier transport and lattice thermal conductivity. Here, we demonstrate that trace incorporation of the lead-free perovskite Cs2TiCl6 enables concurrent optimization of these factors in SnSe0.93. The [TiCl6]2− octahedral framework introduces effective electron donors, while Ti 3d states induce local band flattening, increasing the density-of-states effective mass without severely degrading weighted mobility. Consequently, the 0.5 wt% Cs2TiCl6 sample attains a high power factor of ∼532.1 µW m−1 K−2 at 823 K. Meanwhile, Ti-rich domains together with multi-scale structural defects (strain fields, dislocations, and twin boundaries) substantially intensify phonon scattering, driving the lattice thermal conductivity down to ∼0.32 W m−1 K−1 at 823 K—a 40.6% reduction relative to the pristine specimen. Benefiting from this synergistic carrier and phonon engineering, a peak ZT of ∼1.2 at 823 K is achieved for 0.5 wt% Cs2TiCl6, representing a 179.1% enhancement over undoped SnSe0.93 and outperforming most reported n-type polycrystalline SnSe-based materials. This work establishes trace lead-free perovskite doping as a dual-function strategy—simultaneously enabling band structure modulation and phonon mean free path suppression—offering a viable route toward environmentally benign, high-efficiency n-type SnSe thermoelectrics.
Mohammad Nisar,Adeel Abbas,Junze Zhang,Fu Li,Zhuanghao Zheng,Guangxing Liang,Ping Fan,Yue-Xing Chen
Enhancing the thermoelectric performance of n-type polycrystalline SnSe is essential, addressing challenges posed by elevated thermal conductivity and compromised power factor inherent in its intrinsic p-type characteristics. This investigation utilized solid-state reactions and spark plasma sintering techniques for the synthesis of n-type SnSe. A significant improvement in the figure of merit (ZT) is achieved through strategic reduction in Se concentration and optimization of crystal orientation. The co-doping with Br and Ge further improves the material; Br amplifies carrier concentration, enhancing electrical conductivity, while Ge introduces effective phonon scattering centers. In the Br/Ge co-doped SnSe sample, thermal conductivity dropped to 0.38 Wm⁻¹K⁻¹, yielding a remarkable power factor of 662 µW mK − 2 at 773 K, culminating in a ZT of 1.34. This signifies a noteworthy 605% improvement over the pristine sample, underscoring the pivotal role of Ge doping in enhancing n-type material thermoelectric properties. The enhancement is attributed to Br doping introducing additional electronic states near the valence band, and Ge doping modifying the band structure, fostering resonant states near the conduction band. The Br/Ge co-doping further transforms the band structure, influencing electrical conductivity, Seebeck coefficient, and thermal conductivity, advancing the understanding and application of n-type SnSe materials for superior thermoelectric performance.
Gong Yaru,Dou Wei,Lu Bochen,Zhang Xuemei,Zhu He,Ying Pan,Zhang Qingtang,Liu Yuqi,Li Yanan,Huang Xinqi,Iqbal Muhammad Faisal,Zhang Shihua,Li Di,Zhang Yongsheng,Wu Haijun,Tang Guodong
N -type polycrystalline SnSe is considered as a highly promising candidates for thermoelectric applications due to facile processing, machinability, and scalability. However, existing efforts do not enable a peak ZT value exceeding 2.0 in n -type polycrystalline SnSe. Here, we realized a significant ZT enhancement by leveraging the synergistic effects of divacancy defect and introducing resonance level into the conduction band. The resonance level and increased density of states resulting from tungsten boost the Seebeck coefficient. The combination of the enhanced electrical conductivity (achieved by increasing carrier concentration through WCl 6 doping and Se vacancies) and large Seebeck coefficient lead to a high power factor. Microstructural analyses reveal that the co-existence of divacancy defects (Se vacancies and Sn vacancies) and endotaxial W- and Cl-rich nanoprecipitates scatter phonons effectively, resulting in ultralow lattice conductivity. Ultimately, a record-high peak ZT of 2.2 at 773 K is achieved in n -type SnSe 0.92 + 0.03WCl 6 .
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