@article{21001, abstract = {Copper chalcogenides offer high charge mobility and low lattice thermal conductivity but suffer from structural instability due to dynamic Cu+ migration. Here, we report a colloidal hot-injection synthesis of ternary cesium copper selenide (CsCu5Se3) nanocrystals (NCs), achieving precise control over phase, size, and morphology through tailored precursor-ligand modulation. This strategy enabled systematic exploration of stable and metastable Cs–Cu–Se phases and mechanistic investigation of nucleation and growth, providing insight into phase modulation and dimensional control at the nanoscale. CsCu5Se3 NCs exhibit low lattice thermal conductivity (∼0.5 Wm–1K–1) and an experimental zT of 0.27 at 718 K. Complementary first-principles calculations, consistent with experimental electronic and optical responses, predict a zT of 1.05 at 1000 K. These findings elucidate the formation dynamics of CsCu5Se3 and establish ABZ (A = alkali, B = metal, Z = chalcogen) NCs as tunable platforms for advanced functional applications.}, author = {Patil, Niraj Nitish and Wu, Ruiqi and Fiedler, Christine and Kapuria, Nilotpal and Nan, Bingfei and Navita, Navita and Cabot, Andreu and Ibáñez, Maria and Ryan, Kevin M. and Ganose, Alex M. and Singh, Shalini}, issn = {2380-8195}, journal = {ACS Energy Letters}, number = {1}, pages = {481--488}, publisher = {American Chemical Society}, title = {{Layered alkali-copper selenides: Deciphering thermoelectric properties and reaction pathways for nanostructuring β-CsCu5Se3}}, doi = {10.1021/acsenergylett.5c02909}, volume = {11}, year = {2026}, } @article{18882, abstract = {Ternary liquid-like thermoelectric materials have garnered significant attention due to their ultra-low lattice thermal conductivity. Among these, Ag8SnSe6 stands out for its exceptionally low sound velocity and thermal conductivity. However, the inherent poor electrical conductivity and suboptimal thermoelectric properties of Ag8SnSe6 necessitate further improvement. Here, a novel approach is initiated to enhance the thermoelectric properties of Ag8SnSe6 by combining low-dimensionalization with intrinsic doping. For the first time, this work successfully synthesizes single-phase Ag8SnSe6 nanocrystals, ≈10 nm in size, with the correct phase and composition using a robust and reliable colloidal method. This approach represents a significant improvement over previous reports on this material. Reducing the crystal domains of Ag8SnSe6 to the nanoscale induces quantum confinement effects, increasing the density of states near the Fermi surface. It also introduces additional grain boundaries, which lower the lattice thermal conductivity and simplify structural design. Moreover, incorporating small amounts of Sn nanopowder into the Ag8SnSe6 nanocrystals before consolidation further enhances the thermoelectric performance. Sn acts as a donor dopant, increasing the electronic concentration while at the same time improving their mobility by reducing interface barriers, thus significantly improving the material transport properties. Additionally, the presence of Sn leads to the formation of point defects, dislocations, and secondary phases, which increase phonon scattering and further reduce the thermal conductivity. Through this synergistic optimization, the figure of merit shows a significant increase across a wide temperature range. Overall, a strategy is presented for the controlled preparation of Ag8SnSe6 nanocrystals, the decoupling of their electrical and thermal transport, and the practical application of this material to thermoelectric single-leg modules.}, author = {Zhao, Xueke and Li, Mengyao and Jia, Mochen and Fiedler, Christine and Nan, Bingfei and Yang, Dongwen and Li, Lei and Yuan, Zicheng and Song, Hongzhang and Liu, Yu and Ibáñez, Maria and Wang, Ziyu and Shan, Chongxin and Cabot, Andreu}, issn = {1616-3028}, journal = {Advanced Functional Materials}, number = {24}, publisher = {Wiley}, title = {{Low-dimensional structure modulation in Ag8SnSe6 for enhanced thermoelectric performance}}, doi = {10.1002/adfm.202421449}, volume = {35}, year = {2025}, } @article{19037, abstract = {We present a novel, portable sensor platform that enables concurrent monitoring of surface mass and charge density variations at thin biointerfaces. This platform combines a coplanar-gated field-effect transistor (FET) architecture with grating-coupled surface plasmon resonance (SPR), yielding an integrated disposable sensor chip prepared by nanoimprint and maskless photolithography techniques. The sensor chip design is suitable for scalable production and relies on reduced graphene oxide (rGO), serving as the FET’s semiconductor material for the electronic readout, and a metallic gate electrode surface that is corrugated with a multi-diffractive structure for optical probing with resonantly excited surface plasmons. Together with its integration in a compact instrumentation this results in a form factor optimized solution for dual-mode investigations without compromising the optical or electronic sensor performance. A poly-L-lysine (PLL) – based thin linker layer was deployed at the sensor surface to covalently attach azide-conjugated biomolecules by using incorporated “clickable” dibenzocyclooctyne (DBCO) moieties. Interestingly, the dual-mode measurements allow elucidating the role of the globular nature of the PLL chains when increasing the density of DBCO attached to their backbone, leading to PLL folding and internalization of DBCO moieties, and thus reducing the coupling yield for the used DNA oligomers. We envision that this platform can be employed to studying a range of other biointerface architectures and biomolecular interaction phenomena, which are inherently tied to mass and charge density variations.}, author = {Hasler, Roger and Livio, Pietro A. and Bozdogan, Anil and Fossati, Stefan and Hageneder, Simone and Montes-García, Verónica and Movilli, Jacopo and Moazzenzade, Taghi and Loohuis, Luna and Reiner-Rozman, Ciril and Tamayo, Adrián and Fiedler, Christine and Ibáñez, Maria and Kleber, Christoph and Huskens, Jurriaan and Dostalek, Jakub and Samorì, Paolo and Knoll, Wolfgang}, issn = {1558-1748}, journal = {IEEE Sensors Journal}, number = {7}, pages = {10521--10529}, publisher = {IEEE}, title = {{Dual electronic and optical monitoring of biointerfaces by a grating-structured coplanar-gated field-effect transistor}}, doi = {10.1109/jsen.2025.3533113}, volume = {25}, year = {2025}, } @article{19731, abstract = {In an era of high-resolution displays, powerful design software, and automated plotting tools, one would think that scientific figures would be clearer than ever. Yet, despite numerous editorials, guidelines, and workshops dedicated to improving figure design, poorly constructed figures remain a persistent issue. Editors and experienced researchers have repeatedly highlighted key pitfalls such as cluttered layouts, inconsistent formatting, poor color choices, and misleading visuals. (1−8) Yet, the aforementioned graphical shortcomings continue to plague even high-impact journals. Why? The problem is not a lack of technology; it is a combination of poor design habits, rushed deadlines, and a tendency to treat figures as mere “data dumps” rather than as essential storytelling tools. Many people process information more effectively through visuals, naturally associating concepts easily when presented graphically. A well-crafted figure serves as a narrative within the larger story, making complex ideas more accessible. Unfortunately, visual storytelling often takes a backseat in scientific communication. Scientists are trained to analyze and interpret data, but many default to software-generated plots without considering accessibility or how their figures will be perceived by readers outside their immediate field. Without thoughtful design, figures lose their power to enhance understanding, ultimately limiting the significance of the research itself. In this editorial, we examine the challenges that, in our view, hamper scientific figure design and discuss how thoughtful refinements driven by feedback, iteration, and design principles can enhance clarity and impact visual communication.}, author = {Rayaroth Puthiyaveettil, Aiswarya and Fiedler, Christine and Ibáñez, Maria}, issn = {2694-2461}, journal = {ACS Materials Au}, number = {3}, pages = {438--440}, publisher = {American Chemical Society}, title = {{Let us FIGURE it out: Why do scientists still make “bad” figures?}}, doi = {10.1021/acsmaterialsau.5c00037}, volume = {5}, year = {2025}, } @article{15357, abstract = {There is a growing interest in cost-effective polycrystalline SnSe-based thermoelectric (TE) materials, which are able to replace the high performance but mechanically fragile and costly single-crystalline SnSe. In this study, we present a low-temperature solution-based approach to produce SnSe-PbSe nanocomposites with outstanding TE performance. Our method involves combining surfactant-free SnSe particles with oleate-capped PbSe nanocrystals in specific ratios, followed by thermal annealing and consolidation using spark plasma sintering. These nanocomposites are characterized by distinct compositional and structural properties that significantly impact their transport properties. In particular, the addition of oleate-capped PbSe nanocrystals results in: i) a reduction in the electrostatically adsorbed Na at the surface of the SnSe particles; ii) a reduction of Sn vacancies due to alloying with Pb; iii) an increase in grain boundary density; and iv) the formation of PbSnSe secondary phases. Notably, the SnSe-2.5 %PbSe nanocomposites demonstrate a 30 % decrease in thermal conductivity compared to that of the SnSe matrix. This reduction contributes to a maximum figure of merit (zT) of 1.75 at 788 K with a high average zT value of ca. 1.2 in the medium temperature range of 573–773 K. These values represent one of the highest reported in polycrystalline SnSe materials, showcasing the potential of our fabricated SnSe-PbSe nanocomposites for cost-effective TE applications.}, author = {Liu, Yu and Lee, Seungho and Fiedler, Christine and Spadaro, Maria Chiara and Chang, Cheng and Li, Mingquan and Hong, Min and Arbiol, Jordi and Ibáñez, Maria}, issn = {1385-8947}, journal = {Chemical Engineering Journal}, publisher = {Elsevier}, title = {{Enhancing thermoelectric performance of solutionpProcessed polycrystalline SnSe with PbSe nanocrystals}}, doi = {10.1016/j.cej.2024.151405}, volume = {490}, year = {2024}, } @article{17052, abstract = {Production of thermoelectric materials from solution-processed particles involves the synthesis of particles, their purification and densification into pelletized material. Chemical changes that occur during each one of these steps render them performance determining. Particularly the purification steps, bypassed in conventional solid-state synthesis, are the cause for large discrepancies among similar solution-processed materials. In present work, the investigation focuses on a water-based surfactant free solution synthesis of SnSe, a highly relevant thermoelectric material. We show and rationalize that the number of leaching steps, purification solvent, annealing, and annealing atmosphere have significant influence on the Sn : Se ratio and impurity content in the powder. Such compositional changes that are undetectable by conventional characterization techniques lead to distinct consolidated materials with different types and concentration of defects. Additionally, the profound effect on their transport properties is demonstrated. We emphasize that understanding the chemistry and identifying key chemical species and their role throughout the process is paramount for optimizing material performance. Furthermore, we aim to demonstrate the necessity of comprehensive reporting of these steps as a standard practice to ensure material reproducibility.}, author = {Fiedler, Christine and Calcabrini, Mariano and Liu, Yu and Ibáñez, Maria}, issn = {1521-3773}, journal = {Angewandte Chemie - International Edition}, number = {25}, publisher = {Wiley}, title = {{Unveiling crucial chemical processing parameters influencing the performance of solution-processed inorganic thermoelectric materials}}, doi = {10.1002/anie.202402628}, volume = {63}, year = {2024}, } @article{17124, abstract = {In recent years, solution processes have gained considerable traction as a cost-effective and scalable method to produce high-performance thermoelectric materials. The process entails a series of critical steps: synthesis, purification, thermal treatments, and consolidation, each playing a pivotal role in determining performance, stability, and reproducibility. We have noticed a need for more comprehensive details for each of the described steps in most published works. Recognizing the significance of detailed synthetic protocols, we describe here the approach used to synthesize and characterize one of the highest-performing polycrystalline p-type SnSe. In particular, we report the synthesis of SnSe particles in water and the subsequent surface treatment with CdSe molecular complexes that yields CdSe-SnSe nanocomposites upon consolidation. Moreover, the surface treatment inhibits grain growth through Zenner pinning of secondary phase CdSe nanoparticles and enhances defect formation at different length scales. The enhanced complexity in the CdSe-SnSe nanocomposite microstructure with respect to SnSe promotes phonon scattering and thereby significantly reduces the thermal conductivity. Such surface engineering provides opportunities in solution processing for introducing and controlling defects, making it possible to optimize the transport properties and attain a high thermoelectric figure of merit.}, author = {Fiedler, Christine and Liu, Yu and Ibáñez, Maria}, issn = {1940-087X}, journal = {Journal of Visualized Experiments}, number = {207}, publisher = {MyJove Corporation}, title = {{Solution-processed, surface-engineered, polycrystalline CdSe-SnSe exhibiting low thermal conductivity}}, doi = {10.3791/66278}, volume = {2024}, year = {2024}, } @article{15182, abstract = {Thermoelectric materials convert heat into electricity, with a broad range of applications near room temperature (RT). However, the library of RT high-performance materials is limited. Traditional high-temperature synthetic methods constrain the range of materials achievable, hindering the ability to surpass crystal structure limitations and engineer defects. Here, a solution-based synthetic approach is introduced, enabling RT synthesis of powders and exploration of densification at lower temperatures to influence the material's microstructure. The approach is exemplified by Ag2Se, an n-type alternative to bismuth telluride. It is demonstrated that the concentration of Ag interstitials, grain boundaries, and dislocations are directly correlated to the sintering temperature, and achieve a figure of merit of 1.1 from RT to 100 °C after optimization. Moreover, insights into and resolve Ag2Se's challenges are provided, including stoichiometry issues leading to irreproducible performances. This work highlights the potential of RT solution synthesis in expanding the repertoire of high-performance thermoelectric materials for practical applications.}, author = {Kleinhanns, Tobias and Milillo, Francesco and Calcabrini, Mariano and Fiedler, Christine and Horta, Sharona and Balazs, Daniel and Strumolo, Marissa J. and Hasler, Roger and Llorca, Jordi and Tkadletz, Michael and Brutchey, Richard L. and Ibáñez, Maria}, issn = {1614-6840}, journal = {Advanced Energy Materials}, number = {22}, publisher = {Wiley}, title = {{A route to high thermoelectric performance: Solution‐based control of microstructure and composition in Ag2Se}}, doi = {10.1002/aenm.202400408}, volume = {14}, year = {2024}, } @article{12237, abstract = {Thermoelectric technology requires synthesizing complex materials where not only the crystal structure but also other structural features such as defects, grain size and orientation, and interfaces must be controlled. To date, conventional solid-state techniques are unable to provide this level of control. Herein, we present a synthetic approach in which dense inorganic thermoelectric materials are produced by the consolidation of well-defined nanoparticle powders. The idea is that controlling the characteristics of the powder allows the chemical transformations that take place during consolidation to be guided, ultimately yielding inorganic solids with targeted features. Different from conventional methods, syntheses in solution can produce particles with unprecedented control over their size, shape, crystal structure, composition, and surface chemistry. However, to date, most works have focused only on the low-cost benefits of this strategy. In this perspective, we first cover the opportunities that solution processing of the powder offers, emphasizing the potential structural features that can be controlled by precisely engineering the inorganic core of the particle, the surface, and the organization of the particles before consolidation. We then discuss the challenges of this synthetic approach and more practical matters related to solution processing. Finally, we suggest some good practices for adequate knowledge transfer and improving reproducibility among different laboratories.}, author = {Fiedler, Christine and Kleinhanns, Tobias and Garcia, Maria and Lee, Seungho and Calcabrini, Mariano and Ibáñez, Maria}, issn = {1520-5002}, journal = {Chemistry of Materials}, keywords = {Materials Chemistry, General Chemical Engineering, General Chemistry}, number = {19}, pages = {8471--8489}, publisher = {American Chemical Society}, title = {{Solution-processed inorganic thermoelectric materials: Opportunities and challenges ∇}}, doi = {10.1021/acs.chemmater.2c01967}, volume = {34}, year = {2022}, }