Recent Submissions

  • Efficient bifacial monolithic perovskite/silicon tandem solar cells via bandgap engineering

    de Bastiani, Michele; Mirabelli, Alessandro J.; Hou, Yi; Gota, Fabrizio; Aydin, Erkan; Allen, Thomas; Troughton, Joel; Subbiah, Anand Selvin; Isikgor, Furkan Halis; Liu, Jiang; Xu, Lujia; Chen, Bin; Van Kerschaver, Emmanuel; Baran, Derya; Fraboni, Beatrice; Salvador, Michael F.; Paetzold, Ulrich W.; Sargent, E.; De Wolf, Stefaan (Nature Energy, Springer Science and Business Media LLC, 2021-01-11) [Article]
    Bifacial monolithic perovskite/silicon tandem solar cells exploit albedo—the diffuse reflected light from the environment—to increase their performance above that of monofacial perovskite/silicon tandems. Here we report bifacial tandems with certified power conversion efficiencies >25% under monofacial AM1.5G 1 sun illumination that reach power-generation densities as high as ~26 mW cm–2 under outdoor testing. We investigated the perovskite bandgap required to attain optimized current matching under a variety of realistic illumination and albedo conditions. We then compared the properties of these bifacial tandems exposed to different albedos and provide energy yield calculations for two locations with different environmental conditions. Finally, we present a comparison of outdoor test fields of monofacial and bifacial perovskite/silicon tandems to demonstrate the added value of tandem bifaciality for locations with albedos of practical relevance.
  • Chain Conformation Control of Fluorene-Benzothiadiazole Copolymer Light-Emitting Diode Efficiency and Lifetime

    Wang, Bingjun; Ye, Hao; Riede, Moritz; Bradley, Donal (ACS Applied Materials & Interfaces, American Chemical Society (ACS), 2021-01-07) [Article]
    The β-phase, in which the intermonomer torsion angle of a fraction of chain segments approaches ∼180°, is an intriguing conformational microstructure of the widely studied light-emitting polymer poly(9,9-dioctylfluorene) (PFO). Its generation can in turn be used to significantly improve the performance of PFO emission-layer-based light-emitting diodes (LEDs). Here, we report the generation of β-phase chain segments in a copolymer, 90F8:10BT, containing 90% 9,9-dioctylfluorene (F8) and 10% 2,1,3-benzothiadiazole (BT) units and show that significant improvements in performance also ensue for LEDs with β-phase 90F8:10BT emission layers, generalizing the earlier PFO results. The β-phase was induced by both solvent vapor annealing and dipping copolymer thin films into a solvent/nonsolvent mixture. Subsequent absorption spectra show the characteristic fluorene β-phase peak at ∼435 nm, but luminescence spectra (∼530 nm peak) and quantum yields barely change, with the emission arising following efficient energy transfer to the lowest-lying excited states localized in the vicinity of the BT units. For ∼5% β-phase chain segment fraction relative to 0% β-phase, the LED luminance at 10 V increased by ∼25% to 5940 cd m<sup>-2</sup>, the maximum external quantum efficiency by ∼61 to 1.91%, and the operational stability from 64% luminance retention after 20 h of operation to 90%. Detailed studies addressing the underlying device physics identify a reduced hole injection barrier, higher hole mobility, correspondingly more balanced electron and hole charge transport, and decreased carrier trapping as the dominant factors. These results confirm the effectiveness of chain conformation control for fluorene-based homo- and copolymer device optimization.
  • Direct and continuous generation of pure acetic acid solutions via electrocatalytic carbon monoxide reduction.

    Zhu, Peng; Xia, Chuan; Liu, Chun-Yen; Jiang, Kun; Gao, Guanhui; Zhang, Xiao; Xia, Yang; Lei, Yongjiu; Alshareef, Husam N; Senftle, Thomas P; Wang, Haotian (Proceedings of the National Academy of Sciences of the United States of America, Proceedings of the National Academy of Sciences, 2020-12-31) [Article]
    Electrochemical CO2 or CO reduction to high-value C2+ liquid fuels is desirable, but its practical application is challenged by impurities from cogenerated liquid products and solutes in liquid electrolytes, which necessitates cost- and energy-intensive downstream separation processes. By coupling rational designs in a Cu catalyst and porous solid electrolyte (PSE) reactor, here we demonstrate a direct and continuous generation of pure acetic acid solutions via electrochemical CO reduction. With optimized edge-to-surface ratio, the Cu nanocube catalyst presents an unprecedented acetate performance in neutral pH with other liquid products greatly suppressed, delivering a maximal acetate Faradaic efficiency of 43%,partial current of 200 mA·cm−2, ultrahigh relative purity of up to 98 wt%, and excellent stability of over 150 h continuous operation. Density functional theory simulations reveal the role of stepped sites along the cube edge in promoting the acetate pathway. Additionally, a PSE layer, other than a conventional liquid electrolyte, was designed to separate cathode and anode for efficient ion conductions, while not introducing any impurity ions into generated liquid fuels. Pure acetic acid solutions, with concentrations up to 2 wt% (0.33 M), can be continuously produced by employing the acetate-selective Cu catalyst in our PSE reactor.
  • Ruddlesden–Popper-Phase Hybrid Halide Perovskite/Small-Molecule Organic Blend Memory Transistors

    Gedda, Murali; Yengel, Emre; Faber, Hendrik; Paulus, Fabian; Kreß, Joshua A.; Tang, Ming-Chun; Zhang, Siyuan; Hacker, Christina A.; Kumar, Prashant; Naphade, Dipti R.; Vaynzof, Yana; Volonakis, George; Giustino, Feliciano; Anthopoulos, Thomas D. (Advanced Materials, Wiley, 2020-12-31) [Article]
    Controlling the morphology of metal halide perovskite layers during processing is critical for the manufacturing of optoelectronics. Here, a strategy to control the microstructure of solution-processed layered Ruddlesden-Popper-phase perovskite films based on phenethylammonium lead bromide ((PEA)<sub>2</sub> PbBr<sub>4</sub> ) is reported. The method relies on the addition of the organic semiconductor 2,7-dioctyl[1]benzothieno[3,2-b]benzothiophene (C<sub>8</sub> -BTBT) into the perovskite formulation, where it facilitates the formation of large, near-single-crystalline-quality platelet-like (PEA)<sub>2</sub> PbBr<sub>4</sub> domains overlaid by a ≈5-nm-thin C<sub>8</sub> -BTBT layer. Transistors with (PEA)<sub>2</sub> PbBr<sub>4</sub> /C<sub>8</sub> -BTBT channels exhibit an unexpectedly large hysteresis window between forward and return bias sweeps. Material and device analysis combined with theoretical calculations suggest that the C<sub>8</sub> -BTBT-rich phase acts as the hole-transporting channel, while the quantum wells in (PEA)<sub>2</sub> PbBr<sub>4</sub> act as the charge storage element where carriers from the channel are injected, stored, or extracted via tunneling. When tested as a non-volatile memory, the devices exhibit a record memory window (>180 V), a high erase/write channel current ratio (10<sup>4</sup> ), good data retention, and high endurance (>10<sup>4</sup> cycles). The results here highlight a new memory device concept for application in large-area electronics, while the growth technique can potentially be exploited for the development of other optoelectronic devices including solar cells, photodetectors, and light-emitting diodes.
  • Molecular Doping of a Naphthalene Diimide–Bithiophene Copolymer and SWCNTs for n-Type Thermoelectric Composites

    Liu, Ye; Villalva, Diego Rosas; Sharma, Anirudh; Haque, Mohammed; Baran, Derya (ACS Applied Materials & Interfaces, American Chemical Society (ACS), 2020-12-29) [Article]
    Molecular doping is a powerful tool to tune the thermoelectric (TE) properties of solution-processed semiconductors. In this work, we prepared a binary composite and effectively doped both of its constituents, that is, naphthalene diimide–bithiophene copolymers (PNDI2OD-T2) and single-walled carbon nanotubes (SWCNTs), by a 1H-benzimidazole derivative (N-DMBI). The doped composites show an n-type character and an in-plane TE figure of merit (ZT), exceeding the values obtained with the doped polymers. The use of SWCNTs consistently results in a higher σ with a maximum value above 102 S/cm, resulting in the highest power factor of 18.1 μW/mK2 for an SWCNT loading of 45.5 wt %. Furthermore, an SWCNT content up to 9 wt % does not compromise the low thermal conductivity of the polymer matrices, leading to a ZT value of 0.0045. The n-type composites show good solution processability and relatively stable Seebeck coefficients upon air exposure for 8 months.
  • Light Propagation and Radiative Exciton Transport in Two-Dimensional Layered Perovskite Microwires

    Zheng, Yangzi; Naphade, Rounak; Mondal, Navendu; Bakr, Osman; Mohammed, Omar F.; Gartstein, Yuri N.; Malko, Anton V. (ACS Photonics, American Chemical Society (ACS), 2020-12-29) [Article]
    Layered quasi-two-dimensional perovskites are promising candidates for optoelectronic applications exhibiting excitons with high emission quantum yields, high stability, and ease of bandgap tunability. Here, we demonstrate a long-range (∼100 μm) exciton transfer in a layered perovskite structure (en)4Pb2Br9·3Br, with the ethylene diammonium (en) as a spacer that takes place via the reabsorption of emitted photons. Using the two-objectives setup, we directly map the spatiotemporal dynamics of photoluminescence (PL) from perovskite microwires that reveal a clear spectroscopic signature of photon recycling: the appearance of PL emission rise times and the corresponding elongation of the PL decay as a function of separation distance between the excitation and emission locations. We further show that a kinetic model based on the photon-mediated mechanism of the lateral exciton propagation indeed successfully describes all the salient features of the experimental data and gives an independent assessment of the radiative efficiency of the exciton recombination. Our demonstration points out the possibility of judiciously exploiting light management strategies for future high-performance optoelectronic devices with layered perovskite structures.
  • Semirealistic tight-binding model for Dzyaloshinskii-Moriya interaction

    Hajr, Ahmed; Hariri, Abdulkarim; Manchon, Guilhem; Ghosh, Sumit; Manchon, Aurelien (Physical Review B, American Physical Society (APS), 2020-12-23) [Article]
    In this work, we discuss the nature of Dzyaloshinskii-Moriya interaction (DMI) in transition metal heterostructures. We first derive the expression of DMI in the small-spatial-gradient limit using Keldysh formalism. This derivation provides us with a Green’s function formula that is well adapted to tight-binding Hamiltonians. With this tool, we first uncover the role of orbital mixing: Using both a toy model and a realistic multiorbital Hamiltonian representing transition metal heterostructures, we show that symmetry breaking enables the onset of interfacial orbital momentum that is at the origin of the DMI. We then investigate the contribution of the different layers to the DMI and reveal that it can expand over several nonmagnetic metal layers depending on the Fermi energy, thereby revealing the complex orbital texture of the band structure. Finally, we examine the thickness dependence of DMI on both ferromagnetic and nonmagnetic metal thicknesses and we find that whereas the former remains very weak, the latter can be substantial.
  • Acene Ring Size Optimization in Fused Lactam Polymers Enabling High n-Type Organic Thermoelectric Performance

    Chen, Hu; Moser, Maximilian; Wang, Suhao; Jellett, Cameron; Thorley, Karl; Harrison, George T.; Jiao, Xuechen; Xiao, Mingfei; Purushothaman, Balaji; Alsufyani, Maryam; Bristow, Helen; De Wolf, Stefaan; Gasparini, Nicola; Wadsworth, Andrew; McNeill, Christopher R.; Sirringhaus, Henning; Fabiano, Simone; McCulloch, Iain (Journal of the American Chemical Society, American Chemical Society (ACS), 2020-12-22) [Article]
    Three n-type fused lactam semiconducting polymers were synthesized for thermoelectric and transistor applications via a cheap, highly atom-efficient, and nontoxic transition-metal free aldol polycondensation. Energy level analysis of the three polymers demonstrated that reducing the central acene core size from two anthracenes (A-A), to mixed naphthalene–anthracene (A-N), and two naphthalene cores (N-N) resulted in progressively larger electron affinities, thereby suggesting an increasingly more favorable and efficient solution doping process when employing 4-(2,3-dihydro-1,3-dimethyl-1H-benzimidazol-2-yl)-N,N-dimethylbenzenamine (N-DMBI) as the dopant. Meanwhile, organic field effect transistor (OFET) mobility data showed the N-N and A-N polymers to feature the highest charge carrier mobilities, further highlighting the benefits of aryl core contraction to the electronic performance of the materials. Ultimately, the combination of these two factors resulted in N-N, A-N, and A-A to display power factors (PFs) of 3.2 μW m–1 K–2, 1.6 μW m–1 K–2, and 0.3 μW m–1 K–2, respectively, when doped with N-DMBI, whereby the PFs recorded for N-N and A-N are among the highest reported in the literature for n-type polymers. Importantly, the results reported in this study highlight that modulating the size of the central acene ring is a highly effective molecular design strategy to optimize the thermoelectric performance of conjugated polymers, thus also providing new insights into the molecular design guidelines for the next generation of high-performance n-type materials for thermoelectric applications.
  • Opportunities of Aqueous Manganese-Based Batteries with Deposition and Stripping Chemistry

    Wang, Mingming; Zheng, Xinhua; Zhang, Xiang; Chao, Dongliang; Qiao, Shi Zhang; Alshareef, Husam N.; Cui, Yi; Chen, Wei (Advanced Energy Materials, Wiley, 2020-12-21) [Article]
    Rechargeable aqueous manganese-based batteries have been attracting significant attention owing to their advantages of low cost, high safety, and ease of manufacturing, which are promising attributes for grid-scale energy storage applications. However, most traditional manganese-based batteries with solid-state conversion and intercalation reactions suffer from low capacity and poor long-term cycling stability. The recent novel storage mechanism based on cathode Mn2+/MnO2 deposition/stripping chemistry has fundamentally tackled these issues, enabling a new generation of manganese-based batteries with superior electrochemical performance. Here, the recent advances in aqueous manganese-based batteries with the Mn2+/MnO2 deposition/stripping chemistry are reviewed. A summary of the development of manganese-based batteries with different storage mechanisms is provided and new opportunities for the emerging Mn2+/MnO2 chemistry in the latest generation are highlighted. Then, the current understanding of the Mn2+/MnO2 charge storage mechanism and its potential in manganese-based batteries for large-scale energy storage applications is presented. Moreover, insights into opportunities and future directions for manganese-based batteries with the Mn2+/MnO2 chemistry are proposed.
  • [Cu23(PhSe)16(Ph3P)8(H)6]·BF4: Atomic-Level Insights into Cuboidal Polyhydrido Copper Nanoclusters and Their Quasi-simple Cubic Self-Assembly

    Huang, Renwu; Yin, Jun; Dong, Chunwei; Maity, Partha; Hedhili, Mohamed N.; Nematulloev, Saidkhodzha; Alamer, Badriah Jaber; Ghosh, Atanu; Mohammed, Omar F.; Bakr, Osman (ACS Materials Letters, American Chemical Society (ACS), 2020-12-17) [Article]
    Polyhydrido copper nanoclusters are an emerging class of nanomaterials. Unfortunately, insights into the structural evolution and structure–property relationship of such copper nanoclusters are scant, because of the difficulty of synthesizing and crystallizing nanoclusters with high nuclearity and new morphologies. Here, we report an anisotropic cuboidal polyhydrido copper nanocluster, [Cu23(PhSe)16(Ph3P)8(H)6]·BF4, with a distorted cuboctahedral Cu13 core stabilized by two square protecting motifs and six hydrides. The cuboidal nanoclusters self-assemble into a quasi-simple cubic packing pattern with perfect face-to-face contact of neighboring nanoclusters and interdigitation of intercluster surface ligands. Atomic-level observations reveal the crucial role that subtle synergies between nanocluster geometry and intercluster noncovalent interactions play in guiding nanocluster self-assembly. In addition, a comparison with previously reported analogous metal nanoclusters points to bulky monodentate phosphine ligands as a potent inducing agent for the formation of rectangular hexahedral nanoclusters. These findings have significant implications for the controllable synthesis of polyhedral nanomaterials and their superstructures.
  • Thermoelectric properties of oil fly ash-derived carbon nanotubes coated with polypyrrole

    Salah, Numan; Alhebshi, Nuha; Salah, Yousef N.; Alshareef, Husam N.; Koumoto, Kunihito (Journal of Applied Physics, AIP Publishing, 2020-12-16) [Article]
    Oil fly ash has been reported to be suitable for producing low-cost carbon nanotubes (CNTs). These CNTs exhibit zigzag curved walls with an almost bamboo-like structure. Owing to this structure, these CNTs exhibit very low thermal conductivity as compared to other graphitic carbon materials. They also exhibit relatively low electrical conductivity. However, they exhibit a Seebeck coefficient comparable to that of commercially available CNTs. Therefore, it is of great importance to evaluate the thermoelectric (TE) properties of oil fly ash-derived CNTs. In this study, the TE properties of oil fly ash-derived CNTs were investigated. The CNTs were further coated with polypyrrole (PPy) to enhance their TE performance. PPy was used for the modification because of its attractive TE properties and its suitability as a binder for CNTs. The PPy coating significantly enhanced the electrical conductivity of the CNTs from ∼500 to ∼1300 S/m at room temperature. A small increase in the Seebeck coefficient was also observed. The power factor value increased from 0.1 to 0.6 μW/m K2. At 440 K, the power factor value was 1.4 μW/m K2. The thermal conductivity of the CNTs (∼1 W/m K) decreased significantly by a factor of 10 after the modification with PPy. The power generation characteristics of a single leg module made up of the p-type coated CNTs were investigated under real-time conditions in air. The results demonstrated the potential of the oil fly ash-derived CNTs coated with PPy for applications as TE materials.
  • One-step Six-fold Cyanation of Benzothiadiazole Acceptor Units for Air-Stable High-Performance n-Type Organic Field-Effect Transistors

    Heeney, Martin; Kafourou, Panagiota; Park, Byoungwook; Luke, Joel; Luxi, Tan; Panidi, Julianna; Glöcklhofer, Florian; Kim, Jehan; Anthopoulos, Thomas D.; Kim, Ji-Seon; Lee, Kwanghee; Kwon, Sooncheol (Angewandte Chemie, Wiley, 2020-12-14) [Article]
    We report a new high electron affinity acceptor end group for organic semiconductors, 2,1,3-benzothiadiazole-4,5,6-tricarbonitrile (TCNBT). An n-type organic semiconductor with an indacenodithiophene (IDT) core and TCNBT end groups was synthesized by a six-fold nucleophilic substitution with cyanides on a fluorinated precursor, itself prepared by a direct arylation approach. This one-step chemical modification was found to significantly impact the molecular properties: the fluorinated precursor, TFBT IDT, a poor ambipolar semiconductor, was converted into TCNBT IDT, a good n-type semiconductor. The highly electron-deficient end group TCNBT dramatically decreased the energy of the highest occupied and lowest unoccupied molecular orbitals (HOMO/LUMO) compared to the fluorinated analogue and improved the molecular orientation when utilized in n-type organic field-effect transistors (OFETs). Solution-processed OFETs based on TCNBT IDT exhibited a charge carrier mobility of up to µ e ≈ 0.15 cm 2 V -1 s -1 with excellent ambient stability for 100 hours, highlighting the benefits of the cyanated end group and the synthetic approach.
  • Amphipathic Side Chain of a Conjugated Polymer Optimizes Dopant Location toward Efficient N-Type Organic Thermoelectrics.

    Liu, Jian; Ye, Gang; Potgieser, Hinderikus G O; Koopmans, Marten; Sami, Selim; Nugraha, Mohamad Insan; Villalva, Diego Rosas; Sun, Hengda; Dong, Jingjin; Yang, Xuwen; Qiu, Xinkai; Yao, Chen; Portale, Giuseppe; Fabiano, Simone; Anthopoulos, Thomas D.; Baran, Derya; Havenith, Remco W A; Chiechi, Ryan C; Koster, L. Jan Anton (Advanced materials (Deerfield Beach, Fla.), Wiley, 2020-12-11) [Article]
    There is no molecular strategy for selectively increasing the Seebeck coefficient without reducing the electrical conductivity for organic thermoelectrics. Here, it is reported that the use of amphipathic side chains in an n-type donor-acceptor copolymer can selectively increase the Seebeck coefficient and thus increase the power factor by a factor of ≈5. The amphipathic side chain contains an alkyl chain segment as a spacer between the polymer backbone and an ethylene glycol type chain segment. The use of this alkyl spacer does not only reduce the energetic disorder in the conjugated polymer film but can also properly control the dopant sites away from the backbone, which minimizes the adverse influence of counterions. As confirmed by kinetic Monte Carlo simulations with the host-dopant distance as the only variable, a reduced Coulombic interaction resulting from a larger host-dopant distance contributes to a higher Seebeck coefficient for a given electrical conductivity. Finally, an optimized power factor of 18 µW m$^{-1}$ K$^{-2}$ is achieved in the doped polymer film. This work provides a facile molecular strategy for selectively improving the Seebeck coefficient and opens up a new route for optimizing the dopant location toward realizing better n-type polymeric thermoelectrics.
  • Selective Toluene Detection with Mo2CTx MXene at Room Temperature

    Guo, Wenzhe; Surya, Sandeep Goud; Babar, Vasudeo Pandurang; Ming, Fangwang; Sharma, Sitansh; Alshareef, Husam N.; Schwingenschlögl, Udo; Salama, Khaled N. (ACS Applied Materials & Interfaces, American Chemical Society (ACS), 2020-12-08) [Article]
    MXenes are a promising class of two-dimensional materials with several potential applications, including energy storage, catalysis, electromagnetic interference shielding, transparent electronics, and sensors. Here, we report a novel Mo<sub>2</sub>CT<sub><i>x</i></sub> MXene sensor for the successful detection of volatile organic compounds (VOCs). The proposed sensor is a chemiresistive device fabricated on a Si/SiO<sub>2</sub> substrate using photolithography. The impact of various MXene process conditions on the performance of the sensor is evaluated. The VOCs, such as toluene, benzene, ethanol, methanol, and acetone, are studied at room temperature with varying concentrations. Under optimized conditions, the sensor demonstrates a detection limit of 220 ppb and a sensitivity of 0.0366 Ω/ppm at a toluene concentration of 140 ppm. It exhibits an excellent selectivity toward toluene against the other VOCs. Ab initio simulations demonstrate selectivity toward toluene in line with the experimental results.
  • Impact of Cation Multiplicity on Halide Perovskite Defect Densities and Solar Cell Voltages

    Ledinský, Martin; Vlk, Aleš; Schönfeldová, Tereza; Holovský, Jakub; Aydin, Erkan; Dang, Hoang X.; Hájková, Zdeňka; Landová, Lucie; Valenta, Jan; Fejfar, Antonín; De Wolf, Stefaan (The Journal of Physical Chemistry C, American Chemical Society (ACS), 2020-12-08) [Article]
    Metal-halide perovskites feature very low deep-defect densities, thereby enabling high operating voltages at the solar cell level. Here, by precise extraction of their absorption spectra, we find that the low deep-defect density is unaffected when cations such as Cs+ and Rb+ are added during the perovskite synthesis. By comparing single crystals and polycrystalline thin films of methylammonium lead iodide/bromide, we find these defects to be predominantly localized at surfaces and grain boundaries. Furthermore, generally, for the most important photovoltaic materials, we demonstrate a strong correlation between their Urbach energy and open-circuit voltage deficiency at the solar cell level. Through external quantum yield photoluminescence efficiency measurements, we explain these results as a consequence of nonradiative open-circuit voltage losses in the solar cell. Finally, we define practical power conversion efficiency limits of solar cells by taking into account the Urbach energy.
  • Nanoscale compositional analysis of wurtzite BAlN thin film using atom probe tomography

    Sarker, Jith; Tran, Tinh Binh; AlQatari, Feras S.; Liao, Che-Hao; Li, Xiaohang; Mazumder, Baishakhi (Applied Physics Letters, AIP Publishing, 2020-12-07) [Article]
    In this work, the local atomic level composition of BAlN films with 20% B was investigated using atom probe tomography. Dislocations and elemental clustering were confirmed along which Al atoms tend to segregate. The presence of local compositional heterogeneities (dislocations and small clusters) and impurities is related to the variation of local alloy stoichiometry of the BAlN films. The roughness and interface abruptness of BAlN/AlN were investigated, and a few nm of B and Al composition gradient in BAlN adjacent to the interface was observed. The nanoscale compositional analysis reported here will be crucial for developing BAlN films with a high B content and larger thickness for future high power electronics and optical applications.
  • Unraveling the New Role of an Ethylene Carbonate Solvation Shell in Rechargeable Metal Ion Batteries

    Li, Qian; Cao, Zhen; Wahyudi, Wandi; Liu, Gang; Park, Geon-Tae; Cavallo, Luigi; Anthopoulos, Thomas D.; Wang, Limin; Sun, Yang-Kook; Alshareef, Husam N.; Ming, Jun (ACS Energy Letters, American Chemical Society (ACS), 2020-12-07) [Article]
    Electrolytes play a critical role in controlling metal-ion battery performance. However, the molecular behavior of electrolyte components and their effects on electrodes are not fully understood. Herein, we present a new insight on the role of the most commonly used ethylene carbonate (EC) cosolvent both with the bulk and at the electrolyte-electrode interface. We have discovered a new phenomenon that contributes to stabilizing the electrolyte, besides the well-known roles of dissociating metal salt and forming a solid electrolyte interphase (SEI). As a paradigm, we confirm that EC can form an Li+–EC pair in a priority compared to other kinds of solvents (e.g., ethyl methyl carbonate) and then alter the Li+–solvent interactions in the electrolyte. The Li+–EC pair can dominate the desolvation structure at the electrode interface, therefore suppressing Li+–solvent decomposition due to the higher stability of Li+–EC. Our viewpoint is confirmed in different electrolytes for lithium, sodium, and potassium ion batteries, where the SEI is shown to be limited for stabilizing the electrode in the case of the less stable Li+–solvent pair. Our discovery provides a general explanation for the effect of EC and provides new guidelines for designing more reliable electrolytes for metal (ion) batteries.
  • Device Performance of Emerging Photovoltaic Materials (Version 1)

    Almora, Osbel; Baran, Derya; Bazan, Guillermo C.; Berger, Christian; Cabrera, Carlos I.; Catchpole, Kylie R.; Erten-Ela, Sule; Guo, Fei; Hauch, Jens; Ho-Baillie, Anita; Jacobsson, T. Jesper; Janssen, Rene A. J.; Kirchartz, Thomas; Kopidakis, Nikos; Li, Yongfang; Loi, Maria A.; Lunt, Richard R.; Mathew, Xavier; McGehee, Michael D.; Min, Jie; Mitzi, David B.; Nazeeruddin, Mohammad K.; Nelson, Jenny; Nogueira, Ana F.; Paetzold, Ulrich W.; Park, Nam-Gyu; Rand, Barry P.; Rau, Uwe; Snaith, Henry J.; Unger, Eva; Vaillant-Roca, Lídice; Yip, Hin-Lap; Brabec, Christoph J. (Advanced Energy Materials, Wiley, 2020-12-04) [Article]
    Emerging photovoltaics (PVs) focus on a variety of applications complementing large scale electricity generation. Organic, dye-sensitized, and some perovskite solar cells are considered in building integration, greenhouses, wearable, and indoor applications, thereby motivating research on flexible, transparent, semitransparent, and multi-junction PVs. Nevertheless, it can be very time consuming to find or develop an up-to-date overview of the state-of-the-art performance for these systems and applications. Two important resources for recording research cells efficiencies are the National Renewable Energy Laboratory chart and the efficiency tables compiled biannually by Martin Green and colleagues. Both publications provide an effective coverage over the established technologies, bridging research and industry. An alternative approach is proposed here summarizing the best reports in the diverse research subjects for emerging PVs. Best performance parameters are provided as a function of the photovoltaic bandgap energy for each technology and application, and are put into perspective using, e.g., the Shockley–Queisser limit. In all cases, the reported data correspond to published and/or properly described certified results, with enough details provided for prospective data reproduction. Additionally, the stability test energy yield is included as an analysis parameter among state-of-the-art emerging PVs.
  • MXene improves the stability and electrochemical performance of electropolymerized PEDOT films

    Wustoni, Shofarul; Saleh, Abdulelah; El Demellawi, Jehad K.; Koklu, Anil; Hama, Adel; Druet, Victor; Wehbe, Nimer; Zhang, Yi Zhou; Inal, Sahika (APL Materials, AIP Publishing, 2020-12-01) [Article]
    Poly(3,4-ethylenedioxythiophene) (PEDOT) doped with poly(styrene sulfonate) (PSS) is the most commonly used conducting polymer in organic bioelectronics. However, electrochemical capacitances exceeding the current state-of-the-art are required for enhanced transduction and stimulation of biological signals. The long-term stability of conducting polymer films during device operation and storage in aqueous environments remains a challenge for routine applications. In this work, we electrochemically synthesize a PEDOT composite comprising the water dispersible two-dimensional conducting material Ti3C2 MXene. We find that incorporating MXene as a co-dopant along with PSS leads to PEDOT:PSS:MXene films with remarkably high volumetric capacitance (607.0 ± 85.3 F cm−3) and stability (capacity retention = 78.44% ± 1.75% over 500 cycles), outperforming single dopant-comprising PEDOT films, i.e., PEDOT:PSS and PEDOT:MXene electropolymerized under the same conditions on identical surfaces. The stability of microfabricated PEDOT:PSS:MXene electrodes is evaluated under different conditions, i.e., when the films are exposed to sonication (∼100% retention over 6 min), upon immersion in cell culture media for 14 days (∆|Z| = 2.13%), as well as after continuous electrical stimulation. Furthermore, we demonstrate the use of a PEDOT:PSS:MXene electrode as an electrochemical sensor for sensitive detection of dopamine (DA). The sensor exhibited an enhanced electrocatalytic activity toward DA in a linear range from 1 μM to 100 μM validated in mixtures containing common interferents such as ascorbic acid and uric acid. PEDOT:PSS:MXene composite is easily formed on conductive substrates with various geometries and can serve as a high performance conducting interface for chronic biochemical sensing or stimulation applications.
  • Electrochemical sensors targeting salivary biomarkers: A comprehensive review

    Mani, Veerappan; Beduk, Tutku; Khushaim, Walaa; Ceylan, Ayse Elcin; Timur, Suna; Wolfbeis, Otto S.; Salama, Khaled N. (TrAC Trends in Analytical Chemistry, Elsevier BV, 2020-12) [Article]
    The analysis of salivary markers has grown into a promising non-invasive route for easy, safe, and pain-free monitoring and has the potential to alter the existing way of clinical diagnosis and management. Advancements in sensing technology, the arrival of novel materials, the innovative fabrication technologies, and sampling accuracy have made significant progress and establishing saliva as a fluid for routine analysis. Salivary biomarkers are useful to diagnose not only cardiovascular diseases, bacterial or viral infections but also cancer, diabetes, or Alzheimer’s disease. In addition, saliva is analyzed in toxicology, forensic medicine and drug abuse. Electrochemical assays and sensors are well accepted tools because they allow for fast and cost-effective analysis. Nanomaterials, microfluidics, smartphones, paper-based, flexible and wearable devices have made significant advancements in saliva analysis. This review discusses the recent progress made in electrochemical methodologies for detecting salivary biomarkers

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