Transparent thermoelectric CdO thin films exhibit critical flexibility and thermoelectric performance that require focused research to advance flexible transparent self-powered devices. Here, we demonstrate the superior flexibility of freestanding single-crystalline CdO membranes. These membranes achieve a notable room-temperature power factor of 1.48 μW·cm⁻¹·K⁻² and exhibit superior optical transmittance exceeding 94% in the 550–800 nm range. Crucially, freestanding CdO exhibits exceptional mechanical robustness, retaining >90% electrical conductivity after 1000 bending cycles (radius: 11.5 mm). Microstructure analyses confirm polycrystalline CdO films suffer from grain boundary cracking under bending due to stress concentration, but single-crystal CdO membranes—without grain boundaries to concentrate stress—exhibit better flexibility and resistance to cracking. Furthermore, curvature-induced strain boosts the power factor by 12.8%, providing a curvature-controlled strain engineering strategy to optimize flexible thermoelectric performance. This work establishes freestanding CdO as a highly efficient and flexible thermoelectric material and suggests a fundamental strategy for designing robust smart materials for transparent, self-powered flexible electronics.

Bi₂Se₃ has emerged as a promising thermoelectric (TE) material due to its environmentally benign composition and earth-abundant constituents. However, the practical implementation of Bi₂Se₃-based systems remains challenging due to suboptimal TE performance. This study demonstrates the fabrication of c-axis oriented Bi₂Se₃ thin films through pulsed laser deposition, with subsequent selenization treatment significantly enhancing TE performance through dual optimization of carrier concentration and crystallographic alignment. A strategic post-deposition selenization process effectively mitigates selenium vacancies and correspondingly reduces the carrier concentration to 2.0 × 10¹⁹ cm⁻³ while improving in-plane carrier mobility. A high power factor (PF) of about 9.5 μW·cm⁻¹·K⁻² is achieved at 475 K in the highly c-axis oriented Bi₂Se₃ thin films selenized for about 60 min, outperforming the reported state-of-the-art Bi₂Se₃ films. Demonstrating practical applicability, an 8-leg planar thin-film device generates an exceptional power density of 441.3 μW/cm² under a 25 K temperature gradient, establishing new performance benchmarks for chalcogenide-based microgenerators. These findings provide crucial insights into defect engineering and structural optimization strategies for developing high-performance TE devices compatible with self-powered microelectronic applications.

High-strength high-performance p-type (Bi,Sb)₂Te₃ are of pivotal importance for near-room-temperature thermoelectric conversions, the reliable synthesis and fabrication has been viewed of imperative priority. It is known that the energy-favorable formation of anti-site Sb_Te^’ and vacancy v_Sb^''' acceptor defects from high-temperature syntheses results in additional charge carriers and scattering centers for electrical and phonon transport. However, how p-type (Bi,Sb)₂Te₃ with minimal lattice defects function remains to be scrutinized. Herein, we present the synergistic enhancements of mechanical robustness and thermoelectric property in crystallographic-defect-suppressed pristine (Bi,Sb)₂Te₃ through a simple mechanical alloying combined with spark-plasma-sintering (SPS) process. The Sb_Te^’ and v_Sb^''' acceptor defects were efficiently restrained, contributing to markedly increased charge carrier mobilities. A slightly enlarged band gap of 0.24 eV underpinned enhanced thermoelectric performance for pristine Bi_0.3Sb_1.7Te₃ over a wide temperature range, delivering high zT_{300 K} of 1.16 and zT_ave of 1.21 over 300–473 K. Interestingly, the confined in-situ grain coarsening during SPS with uniform dispersive nanopores readily endowed an ultra-high compressive strength of 206 MPa, surpassing that of reported (Bi,Sb)₂Te₃ so far. A 7-pair module (coupled with n-Bi₂Te₃) was fabricated, demonstrating a competitive ΔT over 70 K at T_hot = 300 K. Furthermore, a power-generation module coupled with n-Mg₃SbBi registered a cutting-edge thermoelectric conversion efficiency of 9.5% at a temperature gradient of 250 K. The strategy eliminates the need of complex processing nor extrinsic doping for pristine (Bi,Sb)₂Te₃, demonstrating great potentials in thermoelectric power generation and cooling applications.

Bi(Te, Se)-based compounds have attracted lots of attention for nearly two centuries as one of the most successful commercial thermoelectric (TE) materials due to their high performance at near room temperature. Compared with 3D bulks, 2D thin films are more compatible with modern semiconductor technology and have unique advantages in the construction of micro- and nano-devices. For device applications, high average TE performance over the entire operating temperature range is critical. Herein, highly c-axis-oriented N-type Bi(Te, Se) epitaxial thin films have been successfully prepared using the pulsed laser deposition technology by adjusting the deposition temperature. The film deposited at ~260 ℃ demonstrate a remarkable average power factor (PF_ave) of ~24.4 μW·cm⁻¹·K⁻² over the temperature range of 305–470 K, higher than most of the state-of-the-art Bi(Te, Se)-based films. Moreover, the estimated average zT value of the film is as high as ~0.81. We then constructed thin-film TE devices by using the above oriented Bi(Te, Se) films, and the maximum output power density of the device can reach up to ~30.1 W/m² under the temperature difference of 40 K. Predictably, the outstanding average TE performance of the highly oriented Bi(Te, Se) thin films will have an excellent panorama of applications in semiconductor cooling and power generation.

AgBi₃S₅ is a new n-type thermoelectric material that is environmentally friendly and composed of elements of earth-abundant, non-toxic and high performance-cost ratio. This compound features an intrinsically low thermal conductivity derived from its complex monoclinic structure. However, the terrible electrical transport properties greatly limited the improvement of thermoelectric performance. Most previous studies considered that carrier concentration is the main reason for low electrical conductivity and focused on improving carrier concentration by aliovalent ion doping. In this work, we found that the critical parameter that restricts the electric transport performance of AgBi₃S₅ was the extremely low carrier mobility instead of the carrier concentration. According to the Pisarenko relationships and density functional theory calculations, Nb doping can sharpen the conduction band of AgBi₃S₅, which contributes to reducing the effective mass and improving the carrier mobility. With a further increase of the Nb doping content, the conduction band convergence can enlarge the effective mass and preserve the carrier mobility. Combined with the decrease in lattice thermal conductivity due to the intensive phone scattering, a maximum ZT value of ~0.50 at 773 K was achieved in Ag_0.97Nb_0.03Bi₃S₅, which was ~109.6% higher than that of pure AgBi₃S₅. This work will stimulate the new exploration of high-performance thermoelectric materials in ternary metal sulfides.

Element doping and nano-inclusion embedding are effective approaches to enhance the electrical conductivities and decrease the lattice thermal conductivities of thermoelectric (TE) materials, respectively. However, the intrinsic low electrical thermal conductivities and high electrical properties are severely sacrificed, and the final figure of merit (ZT) is usually restricted. In this study, Ag doping and Pt quantum dot (QD) embedding were synchronously achieved via embedding Ag/Pt alloy QDs into the higher manganese silicides to avoid the conventional single-element doping strategy. The power factor (at 823 K) was enhanced from 1.57 × 10⁻³ W m⁻¹ K⁻² to 1.82 × 10⁻³ W m⁻¹ K⁻² (~16%) due to the ~18% increase in carrier concentration that was derived from the Ag doping effect. Simultaneously, the lattice thermal conductivity (at 823 K) decreased from 2.65 W m⁻¹ K⁻¹–1.92 W m⁻¹ K⁻¹ (~28%) because of the broadband phonon scattering effect that resulted from the residual Pt QDs inclusions. Synthetically, the optimal ZT value increased by ~52% from 0.42 to 0.64 at 823 K. This study demonstrated that incorporating metastable alloy QDs to obtain element doping and nano-inclusion embedding effects is a novel and feasible means to enhance the ZT value of HMS. This method is also possibly applicable to other alloy QD/TE composites.