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Role of Ag Addition on the Microscopic Material Properties of Ag,Cu In,Ga Se2 Absorbers and Their Effects on Losses in the Open Circuit Voltage of Corresponding Devices
Get PDFAg alloying of Cu In,Ga Se2 CIGSe absorbers in thin film solar cells leads to improved crystallization of these absorber layers at lower substrate temperatures than for Ag free CIGSe thin films as well as to enhanced cation interdiffusion, resulting in reduced Ga In gradients. However, the role of Ag in the microscopic structure property relationships in the Ag,Cu In,Ga Se2 thin film solar cells as well as a correlation between the various microscopic properties of the polycrystalline ACIGSe absorber and open circuit voltage of the corresponding solar cell device has not been reported earlier. In the present work, we study the effect of Ag addition by analyzing the differences in the various bulk, grain boundary, optoelectronic, emission, and absorption edge properties of ACIGSe absorbers with that of a reference CIGSe absorber. By comparing thin film solar cells with similar band gap energies ranging from about 1.1 to about 1.2 amp; 8201;eV, we were able to correlate the differences in their absorber material properties with the differences in the device performance of the corresponding solar cells. Various microscopic origins of open circuit voltage losses were identified, such as strong Ga In gradients and local compositional variations within individual grains of ACIGSe layers, which are linked to absorption edge broadening, lateral fluctuations in luminescence energy distribution, and band tailing, thus contributing to radiative VOC losses. A correlation established between the effective electron lifetime, average grain size, and lifetime at the grain boundaries indicates that enhanced nonradiative recombination at grain boundaries is a major contributor to the overall VOC deficit in ACIGSe solar cells. Although the alloying with Ag has been effective in increasing the grain size and the effective electron lifetime, still, the Ga In gradients and the grain boundary recombination in the ACIGSe absorbers must be reduced further to improve the solar cell performanc
Wavy Graphene Nanoribbons Containing Periodic Eight Membered Rings for Light Emitting Electrochemical Cells
No full textPrecision graphene nanoribbons GNRs offer distinctive physicochemical properties that are highly dependent on their geometric topologies, thereby holding great potential for applications in carbon based optoelectronics and spintronics. While the edge structure and width control has been a popular strategy for engineering the optoelectronic properties of GNRs, non hexagonal ring containing GNRs remain underexplored due to synthetic challenges, despite offering an equally high potential for tailored properties. Herein, we report the synthesis of a wavy GNR wGNR by embedding periodic eight membered rings into its carbon skeleton, which is achieved by the A2B2 type Diels Alder polymerization between dibenzocyclooctadiyne 6 and dicyclopenta[e,l]pyrene 5,11 dione derivative 8 , followed by a selective Scholl reaction of the obtained ladder type polymer LTP precursor. The obtained wGNR, with a length of up to 30 amp; 8197;nm, has been thoroughly characterized by solid state NMR, FT IR, Raman, and UV Vis spectroscopy with the support of DFT calculations. The non planar geometry of wGNR efficiently prevents the inter ribbon amp; 960; amp; 960; aggregation, leading to photoluminescence in solution. Consequently, the wGNR can function as an emissive layer for organic light emitting electrochemical cells OLECs , offering a proof of concept exploration in implementing luminescent GNRs into optoelectronic devices. The fast responding OLECs employing wGNR will pave the way for advancements in OLEC technology and other optoelectronic device
Trapping an Elusive Fe IV Superoxo Intermediate Inside a Self Assembled Nanocage in Water at Room Temperature
No full textMolecular cavities that mimic natural metalloenzymes have shown the potential to trap elusive reaction intermediates. Here, we demonstrate the formation of a rare yet stable Fe IV superoxo intermediate at room temperature subsequent to dioxygen binding at the Fe III site of a Et4N 2[FeIII Cl bTAML ] complex confined inside the hydrophobic interior of a water soluble Pd6L412 nanocage. Using a combination of electron paramagnetic resonance, Mössbauer, Raman IR vibrational, X ray absorption, and emission spectroscopies, we demonstrate that the cage encapsulated complex has a Fe IV oxidation state characterized by a stable S 1 2 spin state and a short Fe O bond distance of amp; 8764;1.70 . We find that the O2 reaction in confinement is reversible, while the formed Fe IV superoxo complex readily reacts when presented with substrates having weak C H bonds, highlighting the lability of the O O bond. We envision that such optimally trapped high valent superoxos can show new classes of reactivities catalyzing both oxygen atom transfer and C H bond activation reaction
Harnessing Surface Dipole for CsPbI3 Perovskite Solar Cells with Poly 3 hexylthiophene
Get PDFThe efficient functioning of perovskite solar cells largely depends on the interaction between perovskite halide materials and the hole transport layer poly 3 hexylthiophene P3HT . However, a high rate of nonradiative recombination often hampers this interaction, leading to poor performance of the solar cells. We have developed a technique to modify the interface using a long chain alkyl halide molecule called n hexyl trimethylammonium bromide to address this issue. This modification technique significantly improves hole extraction, leading to an impressive open circuit voltage of 1.14 amp; 8201;V and a power conversion efficiency of 15.8 for inorganic perovskite CsPbI3 with P3HT as a dopant free hole transport layer. This breakthrough can pave the way for developing more efficient and sustainable solar cell
Members of the paralogous gene family 12 from the Lyme disease agent Borrelia burgdorferi are non specific DNA binding proteins
No full textLyme disease is the most prevalent vector borne infectious disease in Europe and the USA. Borrelia burgdorferi, as the causative agent of Lyme disease, is transmitted to the mammalian host during the tick blood meal. To adapt to the different encountered environments, Borrelia has adjusted the expression pattern of various, mostly outer surface proteins. The function of most B. burgdorferi outer surface proteins remains unknown. We determined the crystal structure of a previously uncharacterized B. burgdorferi outer surface protein BBK01, known to belong to the paralogous gene family 12 PFam12 as one of its five members. PFam12 members are shown to be upregulated as the tick starts its blood meal. Structural analysis of BBK01 revealed similarity to the coiled coil domain of structural maintenance of chromosomes SMC protein family members, while functional studies indicated that all PFam12 members are non specific DNA binding proteins. The residues involved in DNA binding were identified and probed by site directed mutagenesis. The combination of SMC like proteins being attached to the outer membrane and exposed to the environment or located in the periplasm, as observed in the case of PFam12 members, and displaying the ability to bind DNA, represents a unique feature previously not observed in bacteri
C5H9NH3 2CuBr4 A metal organic two ladder quantum magnet
Get PDFLow dimensional quantum magnets are a versatile materials platform for studying the emergent many body physics and collective excitations that can arise even in systems with only short range interactions. Understanding their low temperature structure and spin Hamiltonian is key to explaining their magnetic properties, including unconventional quantum phases, phase transitions, and excited states. We study the metal organic coordination compound C5H9NH3 2CuBr4 and its deuterated counterpart, which upon its discovery was identified as a candidate two leg quantum S 1 2 spin ladder in the strong leg coupling regime. By growing large single crystals and probing them with both bulk and microscopic techniques, we deduce that two previously unknown structural phase transitions take place between 136 and 113 K. The low temperature structure has a monoclinic unit cell that gives rise to two inequivalent spin ladders. We further confirm the absence of long range magnetic order down to 30 mK and investigate the implications of this two ladder structure for the magnetic properties of C5H9NH3 2CuBr4 by analyzing our own specific heat and susceptibility dat
Insights into freeze cast hierarchical water glass foams via in situ time lapse phase contrast enhanced microcomputed tomography Correlating composition, microstructure, and compression failure
No full textWe demonstrate how continuous freeze casting without post treatment sintering may be successfully employed using a pure water glass WG solution to fabricate hierarchically porous foams lacking a morphology gradient along the freeze direction. By adjusting the water content dilution and or the alkali ratio of the solution, we achieved lamellar structures with sub features or cellular structures, with porosities spanning amp; 8764;65 to 83 . The WG foams exhibit astounding mechanical properties; notably, foams with a relatively low density of amp; 8764;0.33 g cm3 demonstrated the highest compressive strength 5 MPa , due to their microstructure and pore morphology. In situ uniaxial compression tests combined with phase contrast enhanced micro computed tomography in a synchrotron revealed bending, buckling, fracture and splitting of the lamellar structures as main failure mechanisms. Our newly developed approach of continuous freeze casting of pure WG solutions with an improved understanding of the relationship between composition, structure, and failure mechanisms provide a basis for a customized design and manufacture of a wide range of freeze cast WG based materials for applications ranging from biomedicine to energy generation and storag
Impact of the nuclear motion on the interparticle Coulombic electron capture
No full textInterparticle Coulombic electron capture ICEC is an environment enabled electron capture process by means of which a free electron can be efficiently attached to a system i.e., ion, atom, molecule, or quantum dot . The excess electron attachment energy is simultaneously transferred to a neighboring system the environment which undergoes ionization. ICEC has been theoretically predicted in van der Waals and hydrogen bonded systems as well as in quantum dot arrays. The theoretical approaches employed in these works range from analytical models to ab initio electronic structure and dynamical calculations. A common assumption in these approaches is that nuclei remain fixed during ICEC. In this paper, we use full explicit electron nuclear dynamics simulations to show that the relative nuclear motion between the two species involved in ICEC enables the electron attachment at kinetic energies of the incoming electron far below the vertical energy threshold i.e., at the equilibrium geometry of the system . ICEC is therefore more efficient than expecte
Can Electrochemical Impedance Spectroscopy be Replaced by Direct Current Techniques in Battery Diagnosis?
Get PDFElectrochemical impedance spectroscopy EIS , a conventional and alternating current AC based technique for impedance measurement, is commonly used in battery diagnosis. However, it requires expensive equipment and demanding operating conditions and is complex and model dependent in data analysis. Recently, novel direct current DC analytics have emerged as an alternative to EIS. They are simple yet powerful, being capable of revealing impedance information that traditionally could only be obtained through EIS and determining Li ion diffusion coefficient. Besides, a complete EIS spectrum can be predicted based on constant current charging curves in the support of machine learning methods. This work highlights the similarities and discrepancies between DC techniques and EIS in the electrochemical analysis of Li ion batteries. Looking ahead, DC techniques may be a promising substitute for EIS in future battery diagnosis, requiring simplified equipment while offering a deep understanding of battery impedance and its underlying electrochemical processe
Techno Economic Assessment of Sustainable H2 Production and Hydrogenation of Chemicals in a Coupled Photoelectrochemical Device
Get PDFPhotoelectrochemical PEC water splitting has been proposed as a promising method to generate sustainable hydrogen, but its competitiveness is hindered by the relatively high cost compared with other generation methods. One strategy to increase the competitiveness of PEC generated H2 is coupling water splitting with hydrogenation reactions that produce higher value chemicals. However, the optimal coupled reaction and the energetic and economic benefits of the coupled concept remain uncertain, especially at larger scales. Here, we conduct a comprehensive techno economic assessment TEA of a hypothetical PEC plant with a 1,000 kg H2 day capacity, considering seven potential hydrogenation reactions. The TEA results show that coupling hydrogenation reaction significantly improves the economic metrics of the system, with acetophenone ACP to 1 phenyl ethanol offering the highest returns. Sensitivity analysis shows that solar to H2 efficiency and H2 to chemicals conversion efficiency are the most critical parameters affecting the levelized cost of hydrogen LCOH of the system. Finally, benchmark conversions that would result in competitive LCOH values that are comparable to that of fossil fuel based H2 are identified, and the potential impact of these coupled PEC hydrogenation reactions on the global H2 market is discusse