Suppressing Deep-Level Trap Toward Over 13% Efficient Solution-Processed Kesterite Solar Cell.

Cu2ZnSn (S,Se)4 (CZTSSe), a promising absorption material for thin-film solar cells, still falls short of reaching the balance limit efficiency due to the presence of various defects and high defect concentration in the thin film. During the high-temperature selenization process of CZTSSe, the diffusion of various elements and chemical reactions significantly influence defect formation. In this study, a NaOH-Se intermediate layer introduced at the back interface can optimize Cu2ZnSnS4 (CZTS)precursor films and subsequently adjust the Se and alkali metal content to favor grain growth during selenization. Through this back interface engineering, issues such as non-uniform grain arrangement on the surface, voids in bulk regions, and poor contact at the back interface of absorber layers are effectively addressed. This method not only optimizes morphology but also suppresses deep-level defect formation, thereby promoting carrier transport at both interfaces and bulk regions of the absorber layer. Consequently, CZTSSe devices with a NaOH-Se intermediate layer improved fill factor, open-circuit voltage, and efficiency by 13.3%. This work initiates from precursor thin films via back interface engineering to fabricate high-quality absorber layers while advancing the understanding regarding the role played by intermediate layers at the back interface of kesterite solar cells.

Anion/Cation Co-Doping to Improve the Thermoelectric Performance of Sn-Enriched n-Type SnSe Polycrystals with Suppressed Lattice Thermal Conductivity.

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.

A Deep Dive into Cu2 ZnSnS4 (CZTS) Solar Cells: A Review of Exploring Roadblocks, Breakthroughs, and Shaping the Future.

Renewable energy is crucial for sustainable future, and Cu2 ZnSnS4 (CZTS) based solar cells shine as a beacon of hope. CZTS, composed of abundant, low-cost, and non-toxic elements, shares similarities with Cu(In,Ga)Se2 (CIGS). However, despite its promise and appealing properties for solar cells, CZTS-based solar cells faces performance challenges owing to inherent issues with CZTS material, and conventional substrate structure complexities. This review critically examines these roadblocks, explores ongoing efforts and breakthroughs, providing insight into the evolving landscape of CZTS-based solar cells research. Furthermore, as an optimistic turn in the field, the review first highlights the crucial need to transition to a superstrate structure for CZTS-based single junction devices, and summarizes the substantial progress made in this direction. Subsequently, dive into the discussion about the fascinating realm of CZTS-based tandem devices, providing an overview of the existing literature as well as outlining the possible potential strategies for enhancing the efficiency of such devices. Finally, the review provides a useful outlook that outlines the priorities for future research and suggesting where efforts should concentrate to shape the future of CZTS-based solar cells.

Back Interface and Absorber Bulk Deep-Level Trap Optimization Enables Highly Efficient Flexible Antimony Triselenide Solar Cell.

The unique 1D crystal structure of Antimony Triselenide (Sb2Se3) offers notable potential for use in flexible, lightweight devices due to its excellent bending characteristics. However, fabricating high-efficiency flexible Sb2Se3 solar cells is challenging, primarily due to the suboptimal contact interface between the embedded Sb2Se3 layer and the molybdenum back-contact, compounded by complex intrinsic defects. This study introduces a novel Molybdenum Trioxide (MoO3) interlayer to address the back contact interface issues in flexible Sb2Se3 devices. Further investigations indicate that incorporating a MoO3 interlayer not only enhances the crystalline quality but also promotes a favorable [hk1] growth orientation in the Sb2Se3 absorber layer. It also reduces the barrier height at the back contact interface and effectively passivates harmful defects. As a result, the flexible Sb2Se3 solar cell, featuring a Mo-foil/Mo/MoO3/Sb2Se3/CdS/ITO/Ag substrate structure, demonstrates exceptional flexibility and durability, enduring large bending radii and multiple bending cycles while achieving an impressive efficiency of 8.23%. This research offers a straightforward approach to enhancing the performance of flexible Sb2Se3 devices, thereby expanding their application scope in the field of photovoltaics.

(Bi,Sb)2 Se3 Alloy Thin Film for Short-Wavelength Infrared Photodetector and TFT Monolithic-Integrated Matrix Imaging.

Short-wavelength infrared photodetectors play a significant role in various fields such as autonomous driving, military security, and biological medicine. However, state-of-the-art short-wavelength infrared photodetectors, such as InGaAs, require high-temperature fabrication and heterogenous integration with complementary metal-oxide-semiconductor (CMOS) readout circuits (ROIC), resulting in a high cost and low imaging resolution. Herein, for the first time, a low-cost, high-performance, high-stable, and thin-film transistor (TFT) ROIC monolithic-integrated (Bi,Sb)2 Se3 alloy thin-film short-wavelength infrared photodetector is reported. The (Bi,Sb)2 Se3 alloy thin-film short-wavelength infrared photodetectors demonstrate a high external quantum efficiency (EQE) of 21.1% (light intensity of 0.76 µW cm-2 ) and a fast response time (3.24 µs). The highest EQE is about two magnitudes than that of the extrinsic photoconduction of Sb2 Se3 (0.051%). In addition, the unpackaged devices demonstrate high electric and thermal stability (almost no attenuation at 120 °C for 312 h), showing potential for in-vehicle applications that may experient such a high temperature. Finally, both the (Bi,Sb)2 Se3 alloy thin film and n-type CdSe buffer layer are directly deposited on the TFT ROIC (with a 64 × 64-pixel array) with a low-temperature process and the material identification and imaging applications are presented. This work is a significant breakthrough in ROIC monolithic-integrated short-wavelength infrared imaging chips.

Electron Transport Layer Engineering Induced Carrier Dynamics Optimization for Efficient Cd-Free Sb2 Se3 Thin-Film Solar Cells.

Antimony selenide (Sb2 Se3 ) is a highly promising photovoltaic material thanks to its outstanding optoelectronic properties, as well as its cost-effective and eco-friendly merits. However, toxic CdS is widely used as an electron transport layer (ETL) in efficient Sb2 Se3 solar cells, which largely limit their development toward market commercialization. Herein, an effective green Cd-free ETL of SnOx is introduced and deposited by atomic layer deposition method. Additionally, an important post-annealing treatment is designed to further optimize the functional layers and the heterojunction interface properties. Such engineering strategy can optimize SnOx ETL with higher nano-crystallinity, higher carrier density, and less defect groups, modify Sb2 Se3 /SnOx heterojunction with better interface performance and much desirable "spike-like" band alignment, and also improve the Sb2 Se3 light absorber layer quality with passivated bulk defects and prolonged carrier lifetime, and therefore to enhance carrier separation and transport while suppressing non-radiative recombination. Finally, the as-fabricated Cd-free Mo/Sb2 Se3 /SnOx /ITO/Ag thin-film solar cell exhibits a stimulating efficiency of 7.39%, contributing a record value for Cd-free substrate structured Sb2 Se3 solar cells reported to date. This work provides a viable strategy for developing and broadening practical applications of environmental-friendly Sb2 Se3 photovoltaic devices.

Suppressing Buried Interface Nonradiative Recombination Losses Toward High-Efficiency Antimony Triselenide Solar Cells.

Antimony triselenide (Sb2 Se3 ) has possessed excellent optoelectronic properties and has gained interest as a light-harvesting material for photovoltaic technology over the past several years. However, the severe interfacial and bulk recombination obviously contribute to significant carrier transport loss thus leading to the deterioration of power conversion efficiency (PCE). In this work, buried interface and heterojunction engineering are synergistically employed to regulate the film growth kinetic and optimize the band alignment. Through this approach, the orientation of the precursor films is successfully controlled, promoting the preferred orientational growth of the (hk1) of the Sb2 Se3 films. Besides, interfacial trap-assisted nonradiative recombination loss and heterojunction band alignment are successfully minimized and optimized. As a result, the champion device presents a PCE of 9.24% with short-circuit density (JSC ) and fill factor (FF) of 29.47 mA cm-2 and 63.65%, respectively, representing the highest efficiency in sputtered-derived Sb2 Se3 solar cells. This work provides an insightful prescription for fabricating high-quality Sb2 Se3 thin film and enhancing the performance of Sb2 Se3 solar cells.

High-Performance Thermoelectric Flexible Ag2Se-Based Films with Wave-Shaped Buckling via a Thermal Diffusion Method.

Herein, an n-type Ag2Se thermoelectric flexible thin film has been fabricated on a polyimide (PI) substrate via a novel thermal diffusion method, and the thermoelectric performance is well-optimized by adjusting the pressure and temperature of thermal diffusion. All of the Ag2Se films are beneficial to grow (013) preferred orientations, which is conducive to performing a high Seebeck coefficient. By increasing the thermal diffusion temperature, the electrical conductivity can be rationally regulated while maintaining the independence of the Seebeck coefficient, which is mainly attributed to the increased electric mobility. As a result, the fabricated Ag2Se thin film achieves a high power factor of 18.25 µW cm-1 K-2 at room temperature and a maximum value of 21.7 µW cm-1 K-2 at 393 K. Additionally, the thermal diffusion method has resulted in a wave-shaped buckling, which is further verified as a promising structure to realize a larger temperature difference by the simulation results of finite element analysis (FEA). Additionally, this unique surface morphology of the Ag2Se thin film also exhibits outstanding mechanical properties, for which the elasticity modulus is only 0.42 GPa. Finally, a flexible round-shaped module assembled with Sb2Te3 has demonstrated an output power of 166 nW at a temperature difference of 50 K. This work not only introduces a new method of preparing Ag2Se thin films but also offers a convincing strategy of optimizing the microstructure to enhance low-grade heat utilization efficiency.

Cadmium-Free Kesterite Thin-Film Solar Cells with High Efficiency Approaching 12.

Cadmium sulfide (CdS) buffer layer is commonly used in Kesterite Cu2 ZnSn(S,Se)4 (CZTSSe) thin film solar cells. However, the toxicity of Cadmium (Cd) and perilous waste, which is generated during the deposition process (chemical bath deposition), and the narrow bandgap (≈2.4 eV) of CdS restrict its large-scale future application. Herein, the atomic layer deposition (ALD) method is proposed to deposit zinc-tin-oxide (ZTO) as a buffer layer in Ag-doped CZTSSe solar cells. It is found that the ZTO buffer layer improves the band alignment at the Ag-CZTSSe/ZTO heterojunction interface. The smaller contact potential difference of the ZTO facilitates the extraction of charge carriers and promotes carrier transport. The better p-n junction quality helps to improve the open-circuit voltage (VOC ) and fill factor (FF). Meanwhile, the wider bandgap of ZTO assists to transfer more photons to the CZTSSe absorber, and more photocarriers are generated thus improving short-circuit current density (Jsc). Ultimately, Ag-CZTSSe/ZTO device with 10 nm thick ZTO layer and 5:1 (Zn:Sn) ratio, Sn/(Sn + Zn): 0.28 deliver a superior power conversion efficiency (PCE) of 11.8%. As far as it is known that 11.8% is the highest efficiency among Cd-free kesterite thin film solar cells.

Charge Transport Enhancement in BiVO4 Photoanode for Efficient Solar Water Oxidation.

Photoelectrochemical (PEC) water splitting in a pH-neutral electrolyte has attracted more and more attention in the field of sustainable energy. Bismuth vanadate (BiVO4) is a highly promising photoanode material for PEC water splitting. Additionally, cobaltous phosphate (CoPi) is a material that can be synthesized from Earth's rich materials and operates stably in pH-neutral conditions. Herein, we propose a strategy to enhance the charge transport ability and improve PEC performance by electrodepositing the in situ synthesis of a CoPi layer on the BiVO4. With the CoPi co-catalyst, the water oxidation reaction can be accelerated and charge recombination centers are effectively passivated on BiVO4. The BiVO4/CoPi photoanode shows a significantly enhanced photocurrent density (Jph) and applied bias photon-to-current efficiency (ABPE), which are 1.8 and 3.2 times higher than those of a single BiVO4 layer, respectively. Finally, the FTO/BiVO4/CoPi photoanode displays a photocurrent density of 1.39 mA cm-2 at 1.23 VRHE, an onset potential (Von) of 0.30 VRHE, and an ABPE of 0.45%, paving a potential path for future hydrogen evolution by solar-driven water splitting.

Tellurium Doping Inducing Defect Passivation for Highly Effective Antimony Selenide Thin Film Solar Cell.

Antimony selenide (Sb2Se3) is emerging as a promising photovoltaic material owing to its excellent photoelectric property. However, the low carrier transport efficiency, and detrimental surface oxidation of the Sb2Se3 thin film greatly influenced the further improvement of the device efficiency. In this study, the introduction of tellurium (Te) can induce the benign growth orientation and the desirable Sb/Se atomic ratio in the Te-Sb2Se3 thin film. Under various characterizations, it found that the Te-doping tended to form Sb2Te3-doped Sb2Se3, instead of alloy-type Sb2(Se,Te)3. After Te doping, the mitigation of surface oxidation has been confirmed by the Raman spectra. High-quality Te-Sb2Se3 thin films with preferred [hk1] orientation, large grain size, and low defect density can be successfully prepared. Consequently, a 7.61% efficiency Sb2Se3 solar cell has been achieved with a VOC of 474 mV, a JSC of 25.88 mA/cm2, and an FF of 64.09%. This work can provide an effective strategy for optimizing the physical properties of the Sb2Se3 absorber, and therefore the further efficiency improvement of the Sb2Se3 solar cells.

Toward High Efficient Cu2 ZnSn(Sx ,Se1- x )4 Solar Cells: Break the Limitations of VOC and FF.

Increasing the fill factor (FF) and the open-circuit voltage (VOC ) simultaneously together with non-decreased short-circuit current density (JSC ) are a challenge for highly efficient Cu2 ZnSn(S,Se)4 (CZTSSe) solar cells. Aimed at such target in CZTSSe solar cells, a synergistic strategy to tailor the recombination in the bulk and at the heterojunction interface has been developed, consisting of atomic-layer deposited aluminum oxide (ALD-Al2 O3 ) and (NH4 )2 S treatment. With this strategy, deep-level CuZn defects are converted into shallower VCu defects and improved crystallinity, while the surface of the absorber is optimized by removing Zn- and Sn-related impurities and incorporating S. Consequently, the defects responsible for recombination in the bulk and at the heterojunction interface are effectively passivated, thereby prolonging the minority carrier lifetime and increasing the depletion region width, which promote carrier collection and reduce charge loss. As a consequence, the VOC deficit decreases from 0.607 to 0.547 V, and the average FF increases from 64.2% to 69.7%, especially, JSC does not decrease. Thus, the CZTSSe solar cell with the remarkable efficiency of 13.0% is fabricated. This study highlights the increased FF together with VOC simultaneously to promote the efficiency of CZTSSe solar cells, which could also be applied to other photoelectronic devices.

Energy Band Alignment by Solution-Processed Aluminum Doping Strategy toward Record Efficiency in Pulsed Laser-Deposited Kesterite Thin-Film Solar Cell.

Kesterite-based Cu2ZnSnS4 (CZTS) thin-film photovoltaics involve a serious interfacial dilemma, leading to severe recombination of carriers and insufficient band alignment at the CZTS/CdS heterojunction. Herein, an interface modification scheme by aluminum doping is introduced for CZTS/CdS via a spin coating method combined with heat treatment. The thermal annealing of the kesterite/CdS junction drives the migration of doped Al from CdS to the absorber, achieving an effective ion substitution and interface passivation. This condition greatly reduces interface recombination and improves device fill factor and current density. The JSC and FF of the champion device increased from 18.01 to 22.33 mA cm-2 and 60.24 to 64.06%, respectively, owing to the optimized band alignment and remarkably enhanced charge carrier generation, separation, and transport. Consequently, a photoelectric conversion efficiency (PCE) of 8.65% was achieved, representing the highest efficiency in CZTS thin-film solar cells fabricated by pulsed laser deposition (PLD) to date. This work proposed a facile strategy for interfacial engineering treatment, opening a valuable avenue to overcome the efficiency bottleneck of CZTS thin-film solar cells.

Crystal Growth Promotion and Defect Passivation by Hydrothermal and Selenized Deposition for Substrate-Structured Antimony Selenosulfide Solar Cells.

Antimony sulfide-selenide (Sb2(S,Se)3) is a promising light-harvesting material for stable and high-efficiency thin-film photovoltaics (PV) because of its excellent light-harvesting capability, abundant elemental storage, and excellent stability. This study aimed to expand the application of Sb2(S,Se)3 solar cells with a substrate structure as a flexible or tandem device. The use of a hydrothermal method accompanied by a postselenization process for the deposition of Sb2(S,Se)3 film based on the solar cell substrate structure was first demonstrated. The mechanism of postselenization treatment on crystal growth promotion of the Sb2(S,Se)3 film and the defect passivation of the Sb2(S,Se)3 solar cell were revealed through different characterization methods. The crystallinity and the carrier transport property of the Sb2(S,Se)3 film improved, and both the interface defect density of the Sb2(S,Se)3/CdS interface and the bulk defect density of the Sb2(S,Se)3 absorber decreased. Through these above-mentioned processes, the transport and collection of electronics can be improved, and the defect recombination loss can be reduced. By using postselenization treatment to optimize the absorber layer, Sb2(S,Se)3 solar cells with the configuration SLG/Mo/Sb2(S,Se)3/CdS/ITO/Ag achieved an efficiency of 4.05%. This work can provide valuable information for the further development and improvement of Sb2(S,Se)3 solar cells.

Achieving High Thermoelectric Performance of Eco-Friendly SnTe-Based Materials by Selective Alloying and Defect Modulation.

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 Sn1.03Te + 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.

Heterojunction Annealing Enabling Record Open-Circuit Voltage in Antimony Triselenide Solar Cells.

Despite the fact that antimony triselenide (Sb2 Se3 ) thin-film solar cells have undergone rapid development in recent years, the large open-circuit voltage (VOC ) deficit still remains as the biggest bottleneck, as even the world-record device suffers from a large VOC deficit of 0.59 V. Here, an effective interface engineering approach is reported where the Sb2 Se3 /CdS heterojunction (HTJ) is subjected to a post-annealing treatment using a rapid thermal process. It is found that nonradiative recombination near the Sb2 Se3 /CdS HTJ, including interface recombination and space charge region recombination, is greatly suppressed after the HTJ annealing treatment. Ultimately, a substrate Sb2 Se3 /CdS thin-film solar cell with a competitive power conversion efficiency of 8.64% and a record VOC of 0.52 V is successfully fabricated. The device exhibits a much mitigated VOC deficit of 0.49 V, which is lower than that of any other reported efficient antimony chalcogenide solar cell.

Crystal Growth Promotion and Defects Healing Enable Minimum Open-Circuit Voltage Deficit in Antimony Selenide Solar Cells.

Antimony selenide (Sb2 Se3 ) is an ideal photovoltaic candidate profiting from its advantageous material characteristics and superior optoelectronic properties, and has gained considerable development in recent years. However, the further device efficiency breakthrough is largely plagued by severe open-circuit voltage (VOC ) deficit under the existence of multiple defect states and detrimental recombination loss. In this work, an effective absorber layer growth engineering involved with vapor transport deposition and post-selenization is developed to grow Sb2 Se3 thin films. High-quality Sb2 Se3 with large compact crystal grains, benign [hk1] growth orientation, stoichiometric chemical composition, and suitable direct bandgap are successfully fulfilled under an optimized post-selenization scenario. Planar Sb2 Se3 thin-film solar cells with substrate configuration of Mo/Sb2 Se3 /CdS/ITO/Ag are constructed. By contrast, such engineering effort can remarkably mitigate the device VOC deficit, owing to the healed detrimental defects, the suppressed interface and space-charge region recombination, the prolonged carrier lifetime, and the enhanced charge transport. Accordingly, a minimum VOC deficit of 0.647 V contributes to a record VOC of 0.513 V, a champion device with highly interesting efficiency of 7.40% is also comparable to those state-of-the-art Sb2 Se3 solar cells, paving a bright avenue to broaden its scope of photovoltaic applications.

Organic Chloride Salt Interfacial Modified Crystallization for Efficient Antimony Selenosulfide Solar Cells.

Antimony selenosulfide, Sb2(SSe)3, is recognized as an excellent photoactive material owing to its light harvesting capability. There is still room for improvement of the film quality for device performance improvement. Herein, an organic chloride salt [diethylamine hydrochloride, DEA(Cl)] has been introduced for fabricating Sb2(SSe)3 solar cells for the first time. A champion device with a power conversion efficiency (PCE) of 9.17% has been achieved with a relatively improved fill factor and open-circuit voltage (VOC). It has been revealed that DEA(Cl) successfully interacts with Sb2(SSe)3, which can facilitate the crystallization process to give rise to the closely packed bigger grain sizes with reduced surface cracks; it successfully suppressed the oxidized Sb species (Sb2O3) in the Sb2(SSe)3 film to give rise to phase purity, thus leading to superior surface morphology and electrical characteristics of DEA(Cl)-modified Sb2(SSe)3 absorber films. Chloride modification is thus efficiently helpful in suppressing interfacial defects, improving junction quality, and optimizing energy-level alignment. This facile interfacial modification demonstrates the remarkable potential for efficient Sb2(SSe)3 solar cells.

Large-Grain Spanning Monolayer Cu2 ZnSnSe4 Thin-Film Solar Cells Grown from Metal Precursor.

The persistent double layer structure whereby two layers with different properties form at the front and rear of absorbers is a critical challenge in the field of kesterite thin-film solar cells, which imposes additional nonradiative recombination in the quasi-neutral region and potential limitation to the transport of hole carriers. Herein, an effective model for growing monolayer CZTSe thin-films based on metal precursors with large grains spanning the whole film is developed. Voids and fine grain layer are avoided successfully by suppressing the formation of a Sn-rich liquid metal phase near Mo back contact during alloying, while grain coarsening is greatly promoted by enhancing mass transfer during grain growth. The desired morphology exhibits several encouraging features, including significantly reduced recombination in the quasi-neutral region that contributes to the large increase of short-circuit current, and a quasi-Ohmic back contact which is a prerequisite for high fill factor. Though this growth mode may introduce more interfacial defects which require further modification, the strategies demonstrated remove a primary obstacle toward higher efficiency kesterite solar cells, and can be applicable to morphology control with other emerging chalcogenide thin films.

Novel Thermal Diffusion Temperature Engineering Leading to High Thermoelectric Performance in Bi2 Te3 -Based Flexible Thin-Films.

Flexible Bi2 Te3 -based thermoelectric devices can function as power generators for powering wearable electronics or chip-sensors for internet-of-things. However, the unsatisfied performance of n-type Bi2 Te3 flexible thin films significantly limits their wide application. In this study, a novel thermal diffusion method is employed to fabricate n-type Te-embedded Bi2 Te3 flexible thin films on flexible polyimide substrates, where Te embeddings can be achieved by tuning the thermal diffusion temperature and correspondingly result in an energy filtering effect at the Bi2 Te3 /Te interfaces. The energy filtering effect can lead to a high Seebeck coefficient ≈160 µV K-1 as well as high carrier mobility of ≈200 cm2 V-1 s-1 at room-temperature. Consequently, an ultrahigh room-temperature power factor of 14.65 µW cm-1 K-2 can be observed in the Te-embedded Bi2 Te3 flexible thin films prepared at the diffusion temperature of 623 K. A thermoelectric sensor is also assembled through integrating the n-type Bi2 Te3 flexible thin films with p-type Sb2 Te3 counterparts, which can fast reflect finger-touch status and demonstrate the applicability of as-prepared Te-embedded Bi2 Te3 flexible thin films. This study indicates that the thermal diffusion method is an effective way to fabricate high-performance and applicable flexible Te-embedded Bi2 Te3 -based thin films.