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Flexible thermoelectric power generation is a competitive candidate for powering wearable electronic devices and chip-sensor of internet-of-things. Nevertheless, the poor thermoelectric performance of n-type flexible thin film limits its application,...

Investigation of physics on two-dimensional curved surface has significant meaning in study of general relativity, inasmuch as its realizability in experimental analogy and verification of faint gravitational effects in laboratory. Several phenomena about dynamics of particles and electromagnetic waves have been explored on curved surfaces. Here we consider Wolf effect, a phenomenon of spectral shift due to the fluctuating nature of light fields, on an arbitrary surface of revolution (SOR).The general expression of the propagation of partially coherent beams propagating on arbitrary SOR is derived and the corresponding evolution of light spectrum is also obtained. We investigate the extra influence of surface topology on spectral shift by defining two quantities, effective propagation distance and effective transverse distance, and compare them with longitudinal and transverse proper lengths. Spectral shift is accelerated when the defined effective quantities are greater than real proper lengths, and vice versa. We also employ some typical SORs, cylindrical surfaces, conical surfaces, SORs generated by power function and periodic peanut-shell shapes, as examples to provide concrete analyses. This work generalizes the research of Wolf effect to arbitrary SORs, and provides a universal method for analyzing properties of propagation compared with that in flat space for any SOR whose topology is known.

Recently, rock-salt lead-free chalcogenide SnTe-based thermoelectric (TE) materials have been considered an alternative to PbTe because of the nontoxic properties of Sn as compared to Pb. However, high carrier concentration that originated from intrinsic Sn vacancies and relatively high thermal conductivity of pristine SnTe lead to poor TE efficiency, which makes room for improving its TE properties. In this study, we present that the Na incorporation into the SnTe matrix is helpful for modifying the electronic band structure, optimization of carrier concentration, introducing dislocations, and kink planes; benefiting from these synergistic effects obviates the disadvantages of SnTe and makes a significant improvement in TE performance. We reveal that Na favorably impacts the structure of electronic bands by valence, conduction band engineering, leading to a nice enhancement in the Seebeck coefficient, which exhibits the highest power factor value of 37.93 μWcm −1 K −2 at 898 K, representing the best result for the SnTe material system. Moreover, a broader phonon spectrum is introduced by new phonon-scattering centers, scattered by dislocations and kink planes which suppressed lattice thermal conductivity to 0.57 Wm −1 K −1 at 898 K, which is much lower than that of pristine SnTe. Ultimately, a maximum ZT of 1.26 at 898 K is achieved in the Sn 1.03 Te + 3% Na sample, which is 97% higher than that of the pristine SnTe, suggesting that SnTe-based materials are a robust candidate for TE applications specifically, an ideal alternative of lead chalcogenides for TE power generation at high temperatures.

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