Formerly the "Solar and Photovoltaic Engineering Research Center (SPERC)"

Recent Submissions

  • Fast water transport and molecular sieving through ultrathin ordered conjugated-polymer-framework membranes

    Shen, Jie; Cai, Yichen; Zhang, Chenhui; Wei, Wan; Chen, Cailing; Liu, Lingmei; Yang, Kuiwei; Ma, Yinchang; Wang, Yingge; Tseng, Chien-Chih; Fu, Jui-Han; Dong, Xinglong; Li, Jiaqiang; Zhang, Xixiang; Li, Lain-Jong; Jiang, Jianwen; Pinnau, Ingo; Tung, Vincent; Han, Yu (Nature Materials, Springer Science and Business Media LLC, 2022-08-08) [Article]
    The development of membranes that block solutes while allowing rapid water transport is of great importance. The microstructure of the membrane needs to be rationally designed at the molecular level to achieve precise molecular sieving and high water flux simultaneously. We report the design and fabrication of ultrathin, ordered conjugated-polymer-framework (CPF) films with thicknesses down to 1 nm via chemical vapour deposition and their performance as separation membranes. Our CPF membranes inherently have regular rhombic sub-nanometre (10.3 × 3.7 Å) channels, unlike membranes made of carbon nanotubes or graphene, whose separation performance depends on the alignment or stacking of materials. The optimized membrane exhibited a high water/NaCl selectivity of ∼6,900 and water permeance of ∼112 mol m−2 h−1 bar−1, and salt rejection >99.5% in high-salinity mixed-ion separations driven by osmotic pressure. Molecular dynamics simulations revealed that water molecules quickly and collectively pass through the membrane by forming a continuous three-dimensional network within the hydrophobic channels. The advent of ordered CPF provides a route towards developing carbon-based membranes for precise molecular separation.
  • Single-step post-production treatment of lead acetate precursor-based perovskite using alkylamine salts for reduced grain-boundary related film defects

    Gebremichael, Zekarias Teklu; Alam, Shahidul; Stumpf, Steffi; Diegel, Marco; Schubert, Ulrich S.; Hoppe, Harald (Nano Select, Wiley, 2022-08-04) [Article]
    Powered by the worldwide efforts of research groups experienced in dye-sensitized, and thin-film solar cells, perovskite solar cells (PSCs) reached a power conversion efficiency of 25.7% within 10 years. However, the presence of defects and trap density within the active layer's grain boundaries commonly operates as non-radiative recombination centers. Hence, intensive efforts have been reported to passivate the inevitable bulk and interface defects of the active layer using additives or post-treatment processing to enhance the efficiency and stability of PSCs. Herein, a facile post-treatment strategy based on wet processing methylammonium lead triiodide, MAPbI3 (prepared from lead acetate and methylammonium iodide precursors) films with organic amine salts (FABr and FAI) is demonstrated. As a result, high-quality films of mixed perovskites (FAxMA1-xPbI3-xBrx and FAxMA1-xPbI3) were obtained. The surface treatment has efficiently passivate the defects in the host film, suppressing the non-radiative carrier recombination. Compared to the control device, the increased open-circuit voltage (from 0.5 V to 1 V) and fill factor (FF) values of the optimized device based on FAxMA1-xPbI3 showed a PCE of 16.13%. And our findings revealed that post-treatment is possible on wet perovskite film aged for a few minutes prior to its post-treatment, which saved the energy used for pre-annealing.
  • Aggregation-Induced Fluorescence Enhancement for Efficient X-ray Imaging Scintillators and High-Speed Optical Wireless Communication

    Wang, Jian-Xin; Wang, Yue; Nadinov, Issatay; Yin, Jun; Gutierrez Arzaluz, Luis; Alkhazragi, Omar; He, Tengyue; Ng, Tien Khee; Eddaoudi, Mohamed; Alshareef, Husam N.; Bakr, Osman; Ooi, Boon S.; Mohammed, Omar F. (ACS Materials Letters, American Chemical Society (ACS), 2022-07-29) [Article]
    Aggregation of some chromophores generates very strong fluorescence signals due to the tight molecular packing and highly restricted vibrational motions in the electronically excited states. Such an aggregation-induced emission enhancement enables great strides in biomedical imaging, security screening, sensing, and light communication applications. Here, we realized efficient utilization of a series of aggregation-induced emission luminogens (AIEgens) in X-ray imaging scintillators and optical wireless communication (OWC) technology. Ultrafast time-resolved laser spectroscopic experiments and high-level density functional theory (DFT) calculations clearly demonstrate that a significant increase in the rotational energy barrier in the aggregated state of AIEgens is observed, leading to highly restricted molecular vibrations and suppressed nonradiative processes. AIEgen-based scintillators exhibit a high X-ray imaging resolution of 16.3 lp mm–1, making them excellent candidates for X-ray radiography and security inspections. In addition, these AIEgens show a broad -3-dB modulation bandwidth of ∼110 MHz and high net data rates of ∼600 Mb/s, demonstrating their high potential for application in the field of high-speed OWC.
  • Correlating acceptor structure and blend nanostructure with the photostability of nonfullerene organic solar cells

    Paleti, Sri Harish Kumar; Hultmark, Sandra; Ramos, Nicolas; Gasparini, Nicola; Emwas, Abdul-Hamid M.; Martin, Jaime; Müller, Christian; Baran, Derya (Solar RRL, Wiley, 2022-07-26) [Article]
    The formation of photo-induced traps resulting in the loss of electron mobility deteriorates the performance of organic solar cells under continuous light soaking. The genesis of these loss mechanisms is elucidated by examining the structural stability of halogenated ITIC derivative films and the phase behavior of the respective binary systems by blending with the donor polymer PBDBT-2F. Under constant illumination, ITIC-4Cl is found to maintain its structural integrity, whereas fluorine on the peripheral moieties of ITIC-4F undergo chemical substitution to form a mixture of ITIC and ITIC-4F. Thermal analysis of the light soaked binary films reveals that ITIC-4Cl loses its crystalline phase while the crystallinity of ITIC-4F does not undergo changes. Further, we show that the addition of a small amount of ITIC-4F as a third component hinders the loss of ITIC-4Cl crystalline phase in bulk-heterojunction blends through the formation of co-crystals. These results suggest that long-range ordering of NFAs does not necessarily improve the photo-stability of organic solar cells and that the addition of a third component, irrespective of the crystalline nature, can prevent changes in bulk-heterojunction blend nanostructure.
  • High-Performance Copper-Doped Perovskite-Related Silver Halide X-ray Imaging Scintillator

    He, Tengyue; Zhou, Yang; Wang, Xiaojia; Yin, Jun; Gutierrez Arzaluz, Luis; Wang, Jian-Xin; Zhang, Yuhai; Bakr, Osman; Mohammed, Omar F. (ACS Energy Letters, American Chemical Society (ACS), 2022-07-26) [Article]
    Scintillators are critical for high-energy radiation detection across a wide array of potential applications, from medical radiography and safety inspections all the way to space exploration. However, constrained by their current shortcomings, including high-temperature and complex fabrication as well as inherent brittleness and fragility among thick films and bulk crystals, traditional scintillators are finding it difficult to meet the rising demand for cost-effective, ecofriendly, and flexible X-ray detection. Here, we describe the development of high-performance and flexible X-ray scintillators based on films of Cu-doped Cs2AgI3 that exhibit ultrahigh X-ray sensitivity. The materials exhibit a high scintillation light yield of up to 82 900 photons/MeV and a low detection limit of 77.8 nGy/s, which is approximately 70 times lower than the dosage for a standard medical examination. Moreover, richly detailed X-ray images of biological tissue and electronic components with a high spatial resolution of 16.2 lp/mm were obtained using flexible, large-area, solution-processed scintillation screens.
  • Simultaneous Performance and Stability Improvement of a p-Type Organic Electrochemical Transistor through Additives

    Hidalgo, Tania C.; Moser, Maximilian; Cendra, Camila; Nayak, Prem Depan; Salleo, Alberto; McCulloch, Iain; Inal, Sahika (Chemistry of Materials, American Chemical Society (ACS), 2022-07-25) [Article]
    Advancements in organic electrochemical transistor (OECT) applications have been largely driven by the development of organic electronic materials that allow for simultaneous ionic and electronic transport in the bulk of their films. These studies focus on achieving high steady-state OECT performance, governed by the electronic charge mobility and the capacitance of the polymer film in the channel, and an often underlooked property is the long-term operational stability. In this work, we present a strategy to improve the performance of p-type OECTs along with operational stability via two additives, i.e., a high-boiling-point solvent (chlorobenzene) and a Lewis acid (tris(pentafluoro phenyl)borane). Addition of a small amount of a cosolvent additive changes the arrangement of glycolated thiophene-based copolymer chains on the substrate toward a direction that allows for more efficient hole transport. The Lewis acid, on the other hand, boosts the OECT stability, mainly by preventing oxidative degradation. Using both additives in the solution grants OECTs with high operational stability and performance through changes in the film microstructure and the polymer’s sensitivity to oxygen. This study highlights the use of additives as a means to enhance the OECT figure of merits without the need for new polymer synthesis.
  • Large Spin Coherence Length and High Photovoltaic Efficiency of the Room Temperature Ferrimagnet Ca2FeOsO6 by Strain Engineering

    Rout, Paresh Chandra; Schwingenschlögl, Udo (Advanced Science, Wiley, 2022-07-21) [Article]
    The influence of epitaxial strain on the electronic, magnetic, and optical properties of the distorted double perovskite Ca2FeOsO6 is studied. These calculations show that the compound realizes a monoclinic structure with P21/n space group from −6% to +6% strain. While it retains ferrimagnetic ordering with a net magnetic moment of 2 μB per formula unit at low strain, it undergoes transitions into E-antiferromagnetic and C-antiferromagnetic phases at −5% and +5% strain, respectively. It is shown that spin frustration reduces the critical temperature of the ferrimagnetic ordering from the mean field value of 600–350 K, in excellent agreement with the experimental value of 320 K. It is also shown that the critical temperature can be tuned efficiently through strain and that the spin coherence length surpasses that of Sr2FeMoO6 under tensile strain. An indirect-to-direct bandgap transition is observed at +5% strain. Localization of the valence and conduction states on different transition metal sublattices enables efficient electron–hole separation upon photoexcitation. The calculated spectroscopic limited maximum efficiency of up to 33% points to excellent potential of Ca2FeOsO6 in solar cell applications.
  • Direct Band Gap in Multilayer Transition Metal Dichalcogenide Nanoscrolls with Enhanced Photoluminescence

    Lin, Ci; Cai, Liang; Fu, Jui-Han; Sattar, Shahid; Wang, Qingxiao; Wan, Yi; Tseng, Chien-Chih; Yang, Chih-Wen; Aljarb, Areej; Jiang, Ke; Huang, Kuo-Wei; Li, Lain-Jong; Canali, Carlo Maria; Shi, Yumeng; Tung, Vincent (ACS Materials Letters, American Chemical Society (ACS), 2022-07-20) [Article]
    A direct band gap that solely exists in monolayer semiconducting transition metal dichalcogenides (TMDs) endows strong photoluminescence (PL) features, whereas multilayer TMD structures exhibit quenched PL due to the direct-to-indirect band gap transition. We demonstrate multilayer TMD (such as MoS2 and WS2) nanoscrolls with a preserved direct band gap fabricated by an effective and facile method of solvent-driven self-assembly. The resultant multilayer nanoscrolls, exhibiting up to 11 times higher PL intensity than the remanent monolayer, are carefully characterized using PL spectroscopy. Significantly enlarged interlayer distances and modulated interlayer coupling in the fabricated nanostructures are unveiled by cross-sectional scanning transmission electron microscopy, atomic force microscopy, and Raman spectroscopy. The preservation of direct band gap features is further evidenced by density functional theory calculations using the simplified bilayer model with an experimentally obtained 15 Å interlayer distance. The modulation of the PL intensity as an indicator of the band gap crossover in the TMD nanoscrolls is demonstrated by removing the acetone molecules trapped inside the interlayer space. The general applicability of the method presents an opportunity for large-scale fabrication of a plethora of multilayer TMD nanoscrolls with direct band gaps.
  • Bifacial perovskite/silicon tandem solar cells

    de Bastiani, Michele; Subbiah, Anand Selvin; Babics, Maxime; Ugur, Esma; Xu, Lujia; Liu, Jiang; Allen, Thomas; Aydin, Erkan; De Wolf, Stefaan (Joule, Elsevier BV, 2022-07-20) [Article]
    Perovskite/silicon tandem solar cells are a rapidly emerging class of high-efficiency photovoltaic (PV) devices that have demonstrated excellent power conversion efficiencies (PCEs) while promising low-cost manufacturing. In recent years, this technology has been pushed increasingly closer to market entrance. Yet, for true commercial success, PCEs also need to be stable, in line with the warranty certificates of commercial crystalline-silicon (c-Si) PV modules. Bifacial tandem solar cells that collect light at both their sunward and rear side by exploiting the albedo—the scattered and reflected photons from the ground—offer a promising pathway toward a greater stability and energy yield. Thanks to the additional photons arising from the albedo, bifacial solar cells may generate a current larger than their conventional monofacial counterparts, enabling a higher performance. For bifacial monolithic tandems, exploiting such current enhancement requires current matching between top and bottom cells, which mandates the use of a bromide-lean, narrow-band-gap perovskite that is known to suppress halide segregation, thereby significantly improving device stability. In this perspective, we discuss bifacial perovskite/silicon tandem technology in depth, highlighting its great appeal, thanks to its combination of enhanced performance and improved stability with promising low costs, thereby representing a key future technology at the utility scale that can contribute to the formation of a carbon-neutral sustainable economy.
  • Low-defect-density WS2 by hydroxide vapor phase deposition

    Wan, Yi; Li, En; Yu, Zhihao; Huang, Jing-Kai; Li, Ming-yang; Chou, Ang-Sheng; Lee, Yi-Te; Lee, Chien-Ju; Hsu, Hung-Chang; Zhan, Qin; Aljarb, Areej; Fu, Jui-Han; Chiu, Shao-Pin; Wang, Xinran; Lin, Juhn-Jong; Chiu, Ya-Ping; Chang, Wen-Hao; Wang, Han; Shi, Yumeng; Lin, Nian; Cheng, Yingchun; Tung, Vincent; Li, Lain-Jong (Nature Communications, Springer Science and Business Media LLC, 2022-07-18) [Article]
    Two-dimensional (2D) semiconducting monolayers such as transition metal dichalcogenides (TMDs) are promising channel materials to extend Moore’s Law in advanced electronics. Synthetic TMD layers from chemical vapor deposition (CVD) are scalable for fabrication but notorious for their high defect densities. Therefore, innovative endeavors on growth reaction to enhance their quality are urgently needed. Here, we report that the hydroxide W species, an extremely pure vapor phase metal precursor form, is very efficient for sulfurization, leading to about one order of magnitude lower defect density compared to those from conventional CVD methods. The field-effect transistor (FET) devices based on the proposed growth reach a peak electron mobility ~200 cm2/Vs (~800 cm2/Vs) at room temperature (15 K), comparable to those from exfoliated flakes. The FET device with a channel length of 100 nm displays a high on-state current of ~400 µA/µm, encouraging the industrialization of 2D materials.
  • Charge transfer mediated triplet excited state formation in donor-acceptor-donor BODIPY: Application for recording of holographic structures in photopolymerizable glass

    Mikulchyk, Tatsiana; Karuthedath, Safakath; De Castro, Catherine S. P.; Buglak, Andrey A.; Sheehan, Aimee; Wieder, Aaron; Laquai, Frédéric; Naydenova, Izabela; Filatov, Mikhail A. (JOURNAL OF MATERIALS CHEMISTRY C, Royal Society of Chemistry (RSC), 2022-07-18) [Article]
    Donor–acceptor–donor BODIPY triads bearing anthracene or pyrene as electron donating subunits were prepared through a stepwise synthesis. Photoinduced electron transfer and formation of long-lived triplet excited states via spin–orbit charge transfer intersystem crossing (SOCT-ISC) was studied by steady-state and ultrafast pump-probe spectroscopy and further supported by DFT computations. New BODIPYs were found to form triplet states and sensitize singlet oxygen in both polar and non-polar solvents which is unusual for photosensitizers operating via SOCT-ISC. BODIPY-anthracene triad (ABA) was used as a photosensitizer component in a photopolymerizable glass that was prepared by a four-step sol–gel process. ABA in combination with N-phenylglycin (NPG) showed the ability to initiate a free-radical polymerization of methacrylate monomers under 532 nm irradiation thus allowing for holographic recording of diffractive structures. High diffraction efficiency (up to 87%) obtained for ABA-NPG containing glass as compared to a reference diiodo-BODIPY (I2BDP) demonstrates for the first time that heavy-atom-free SOCT-ISC photosensitizers can efficiently operate in the solid state.
  • Addition of Diquat Enhances the Electron Mobility in Various Non-Fullerene Acceptor Molecules

    Nugraha, Mohamad; Gedda, Murali; Firdaus, Yuliar; Scaccabarozzi, Alberto D.; Zhang, Weimin; Alshammari, Sanaa Hayel Nazil; Aniés, Filip; Adilbekova, Begimai; Emwas, Abdul-Hamid; McCulloch, Iain; Heeney, Martin; Tsetseris, Leonidas; Anthopoulos, Thomas D. (Advanced Functional Materials, Wiley, 2022-07-15) [Article]
    Molecular doping of organic semiconductors is often used to enhance their charge transport characteristics. Despite its success, however, most studies to date concern p-doping with considerably fewer reports involving n-dopants. Here, n-doping of organic thin-film transistors (OTFTs) based on several non-fullerene acceptor (NFA) molecules using the recently developed diquat (DQ) as a soluble molecular dopant is reported. The low ionization potential of DQ facilitates efficient electron transfer and subsequent n-doping of the NFAs, resulting in a consistent increase in the electron field-effect mobility. Solution-processed BTP-eC9 and N3-based OTFTs exhibit significant increase in the electron mobility upon DQ doping, with values increasing from 0.02 to 0.17 cm2 V–1 s–1 and from 0.2 to 0.57 cm2 V–1 s–1, respectively. A remarkable electron mobility of >1 cm2 V–1 s–1 is achieved for O-IDTBR transistors upon optimal doping with DQ. The enhanced performance originates primarily from synergistic effects on electronic transport and changes in morphology, including: i) significant reduction of contact resistances, ii) formation of larger crystalline domains, iii) change of preferred crystal orientation, and iv) alteration in molecular packing motif. This work demonstrates the universality of DQ as an electronic additive for improving electron transport in OTFTs.
  • Lecithin Capping Ligands Enable Ultrastable Perovskite-Phase CsPbI3 Quantum Dots for Rec. 2020 Bright-Red Light-Emitting Diodes

    Mir, Wasim Jeelani; Alamoudi, Ahmed; Yin, Jun; Yorov, Khursand E.; Maity, Partha; Naphade, Rounak; Shao, Bingyao; Wang, Jiayi; Lintangpradipto, Muhammad Naufal; Nematulloev, Saidkhodzha; Emwas, Abdul-Hamid M.; Genovese, Alessandro; Mohammed, Omar F.; Bakr, Osman (Journal of the American Chemical Society, American Chemical Society (ACS), 2022-07-14) [Article]
    Bright-red light-emitting diodes (LEDs) with a narrow emission line width that emit between 620 and 635 nm are needed to meet the latest industry color standard for wide color gamut displays, Rec. 2020. CsPbI3 perovskite quantum dots (QDs) are one of the few known materials that are ideally suited to meet these criteria. Unfortunately, CsPbI3 perovskite QDs are prone to transform into a non-red-emitting phase and are subject to further degradation mechanisms when their luminescence wavelength is tuned to match that of the Rec. 2020 standard. Here, we show that zwitterionic lecithin ligands can stabilize the perovskite phase of CsPbI3 QDs for long periods in air for at least 6 months compared to a few days for control samples. LEDs fabricated with our ultrastable lecithin-capped CsPbI3 QDs exhibit an external quantum efficiency (EQE) of 7.1% for electroluminescence centered at 634 nm─a record for all-inorganic perovskite nanocrystals in Rec. 2020 red. Our devices achieve a maximum luminance of 1391 cd/m2 at 7.5 V, and their operational half-life is 33 min (T50) at 200 cd/m2─a 10-fold enhancement compared to control samples. Density functional theory results suggest that the surface strain in CsPbI3 QDs capped with the conventional ligands, oleic acid and oleylamine, contributes to the instability of the perovskite structural phase. On the other hand, lecithin binding induces virtually no surface strain and shows a stronger binding tendency for the CsPbI3 surface. Our study highlights the tremendous potential of zwitterionic ligands in stabilizing the perovskite phase and particle size of CsPbI3 QDs for various optoelectronic applications.
  • Recent Advances in Chemistry/Materials (Saudi Arabia)

    Aziz, Md. Abdul; Hossain, M. Mozahar; Mohammed, Omar F. (The Chemical Record, Wiley, 2022-07-08) [Article]
    Saudi Arabia in recent years has made considerable progress in the field of chemistry and material science, especially in topics, such as nanotechnology, energy storage, and photovoltaics. This special issue comprises high-quality contributions by researchers in the country.
  • Photophysics of Defect-Passivated Quasi-2D (PEA)2PbBr4 Perovskite Using an Organic Small Molecule

    Khan, Jafar Iqbal; Gedda, Murali; Wang, Mingcong; Yengel, Emre; Kreß, Joshua A.; Vaynzof, Yana; Anthopoulos, Thomas D.; Laquai, Frédéric (ACS Energy Letters, American Chemical Society (ACS), 2022-07-07) [Article]
    2D Ruddlesden–Popper perovskites are promising candidates for energy-harvesting applications because of their tunable optical properties and ambient stability. Moreover, they are solution-processable and compatible with scalable manufacturing via various printing techniques. However, such methods often induce large degrees of heterogeneity because of poorly controlled crystallization. We address this issue by blending the well-known 2D perovskite (PEA)2PbBr4 with an organic small molecule, C8-BTBT. Terahertz (THz) absorption and temperature-dependent photoluminescence (PL) spectroscopy studies revealed changes in the photophysical properties of the perovskite without affecting its structural integrity upon adding C8-BTBT. The inclusion of trace amounts of C8-BTBT results in defect passivation both at perovskite platelet boundaries and at surfaces, as indicated by increased carrier lifetimes and substantially increased photoluminescence quantum yields (PLQY). This improves the responsivity of photodetectors using the 2D perovskite as an active layer. Our study highlights a straightforward strategy for fabricating high-quality 2D perovskites via large-area processing techniques.
  • Two-dimensional ferroelectricity and antiferroelectricity for next-generation computing paradigms

    Xue, Fei; Ma, Yinchang; Wang, Hua; Luo, Linqu; Xu, Yang; Anthopoulos, Thomas D.; Lanza, Mario; Yu, Bin; Zhang, Xixiang (Matter, Elsevier BV, 2022-07-06) [Article]
    Ferroelectricity (FE) and antiferroelectricity (AFE) are correlated physical phenomena that, in the two-dimensional (2D) limit, exhibit unprecedented rich physics in terms of polarization creation, stabilization, and switching. By modulating the proximity effect of polarization, 2D FE and AFE can unexpectedly demonstrate reversible transformations. Moreover, these fundamental physics can spur innovation in memory devices toward emerging computation paradigms, including neuromorphic computing and sensing. In this perspective, we discuss the emergent physics of 2D FE and AFE and highlight phase transitions with different approaches between them. We also outline advanced device applications for next-generation computing and provide possible future research lines.
  • Unraveling the Correlation between Raman and Photoluminescence in Monolayer MoS2 through Machine Learning Models

    Lu, Ang-Yu; Martins, Luiz Gustavo Pimenta; Shen, Pin-Chun; Chen, Zhantao; Park, Ji-Hoon; Xue, Mantian; Han, Jinchi; Mao, Nannan; Chiu, Ming-Hui; Palacios, Tomás; Tung, Vincent; Kong, Jing (Advanced Materials, Wiley, 2022-07-05) [Article]
    Two-dimensional (2D) transition metal dichalcogenides (TMDCs) with intense and tunable photoluminescence (PL) have opened up new opportunities for optoelectronic and photonic applications such as light-emitting diodes, photodetectors, and single-photon emitters. Among the standard characterization tools for 2D materials, Raman spectroscopy stands out as a fast and non-destructive technique capable of probing material crystallinities and perturbations such as doping and strain. However, a comprehensive understanding of the correlation between photoluminescence and Raman spectra in monolayer MoS2 remains elusive due to its highly nonlinear nature. Here, we systematically explore the connections between PL signatures and Raman modes, providing comprehensive insights into the physical mechanisms correlating PL and Raman features. Our analysis further disentangles the strain and doping contributions from the Raman spectra through machine learning models. First, we deploy a DenseNet to predict PL maps by spatial Raman maps. Moreover, we apply a gradient boosted trees model (XGBoost) with Shapley additive explanation (SHAP) to bridge the impact of individual Raman features in PL features, allowing us to link the strain and doping of monolayer MoS2. Last, we adopt a support vector machine (SVM) to project PL features on Raman frequencies. Our work may serve as a methodology for applying machine learning in 2D material characterizations and providing the knowledge for tuning and synthesizing 2D semiconductors for high-yield photoluminescence.
  • An effective method of reconnoitering current–voltage (IV) characteristics of organic solar cells

    Meitzner, Rico; Madalaimuthu, Jose Prince; Alam, Shahidul; Islam, Md Moidul; Peiler, Sebastian; Anand, Aman; Ahner, Johannes; Hager, Martin D.; Schubert, Ulrich S.; Zou, Yingping; Laquai, Frédéric; Hoppe, Harald (Journal of Applied Physics, AIP Publishing, 2022-07-05) [Article]
    Current–voltage ( IV) characterization is the most fundamental measurement performed on solar cells. This measurement is commonly used to extract basic solar cell parameters, such as open circuit voltage, short circuit current density, fill factor, and power conversion efficiency. We were able to obtain a fast tool to find defective behavior using Simulation Program with Integrated Circuit Emphasis simulations and generate an understanding of which device property can create such defective behaviors by analyzing the second derivative of IV curves.
  • Solar-driven ultrafast lithium extraction from low-grade brine using microfluidics-mediated vortex in scalable electrochemical reactors

    Zhang, Xianyun; Li, Zhen; Liu, Jiang; Xu, Fuzong; Zheng, Leiliang; De Wolf, Stefaan; Lai, Zhiping; Lu, Xu (Research Square Platform LLC, 2022-07-05) [Preprint]
    Electrochemical lithium (Li) extraction from low-grade salt lake brine, when powered by off-grid renewables, represents a potential approach to meeting the substantially increasing demand for battery-grade Li2CO3. However, this technology has been drastically challenged by the low extraction rate and high production cost, largely due to the lack of research on reactor engineering and system scale-out. Herein, we rationally designed a scalable spiral-microstructured electrochemical reactor (SMER) to accomplish ultrafast and economical Li extraction under harsh brine conditions by virtue of significantly accelerated mass transfer. We showcased that the SMER was stably operated at a Li extraction rate over 5.6 times as much as that of state-of-art devices, and could be up-scaled for commercial production of battery-grade Li2CO3 driven by solar cells. This work lays the ground for sustainable Li extraction from remote low-grade salt lake brine and can be readily applied to more minable Li reserves/resources.
  • Double-Cable Conjugated Polymers with Pendent Near-Infrared Electron Acceptors for Single-Component Organic Solar Cells

    Liang, Shijie; Liu, Baiqiao; Karuthedath, Safakath; Wang, Jing; He, Yakun; Tan, Wen Liang; Li, Hao; Xu, Yunhua; Li, Ning; Hou, Jianhui; Tang, Zheng; Laquai, Frédéric; McNeill, Christopher R.; Brabec, Christoph J.; Li, Weiwei (Angewandte Chemie, Wiley, 2022-07-04) [Article]
    Double-cable conjugated polymers with near-infrared (NIR) electron acceptors are synthesized for use in single-component organic solar cells (SCOSCs). Through the development of a judicious synthetic pathway, the highly sensitive nature of the 2-(3-oxo-2,3-dihydroinden-1-ylidene)malononitrile (IC)-based electron acceptors in basic and protonic solvents is overcome. In addition, an asymmetric design motif is adopted to optimize the packing of donor and acceptor segments, enhancing charge separation efficiency. As such, the new double-cable polymers are successfully applied in SCOSCs, providing an efficiency of over 10% with a broad photo response from 300 to 850 nm and exhibiting excellent thermal/light stability. These results demonstrate the powerful design of NIR-acceptor-based double-cable polymers and will enable SCOSCs to enter a new stage.

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