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Minimizing Recombination at the Perovskite C60 Interface through a Volatile Highly Dense Molecular Interlayer
Get PDFAdvancing inverted perovskite solar cells requires effective strategies to mitigate nonradiative recombination at the perovskite C60 interface. Here, we report a volatile material that forms a thin, dense interlayer that essentially eliminates the C60 induced nonradiative interfacial recombination loss despite not directly passivating the perovskite surface. Ultraviolet photoelectron spectroscopy highlights that the molecule forms a positive dipole layer on the surface that aligns the perovskite and C60 energy levels for electron conduction. Furthermore, the molecule s volatile nature allows the use of a high concentration solution that enables a high surface coverage likely gt;99 without increasing the thickness. The combination of these two effects yields an effective approach to suppressing interface recombination. The resulting triple cation perovskite solar cells achieved a power conversion efficiency of gt;25 and the devices maintain gt;90 of their initial efficiency after 1200 h of operation. Furthermore, the molecule is broadly applicable to various perovskite compositions and bandgap
Impact of Minimal Silver Incorporation on Chalcopyrite Absorbers Origins for Improved Open Circuit Voltages in Ag,Cu In,Ga Se2 Solar Cells
Get PDFThe influence of minimal amounts of Ag 0.5 1.4 at on elemental distribution and crystalline quality of Ag,Cu In,Ga Se2 ACIGSe absorbers grown by the three stage coevaporation without added alkali elements is reported. The elemental ratios affect the amount of Ag to be uniformly incorporated into the chalcopyrite absorber and the open circuit voltage VOC of the ACIGSe solar cell devices. Ag containing absorbers deposited at 530 C achieve a best photoconversion efficiency of 18.2 . Due to an increased VOC, ACIGSe absorbers perform better than their Ag free variants at low deposition temperatures. The factors contributing to this increased VOC of low temperature devices are 1 enhanced elemental Ga and In interdiffusion and hence their spatial distribution across the absorber thickness, leading to an increase in the minimum bandgap, 2 an improved absorber crystalline quality with larger grains resulting in high quasi Fermi level splitting and lower nonradiative losses. The photoluminescence data obtained on the ACIGSe absorbers reveal the corresponding variations in their bandgap and photoluminescence quantum yield. These material level insights into Ag incorporation in chalcopyrite help to advance the development of chalcopyrite based tandem solar cells, which so far is limited by the requirement of high deposition temperature
Iron tetraphenylporphyrin chloride metal substrate interaction mediated by a graphene buffer layer
No full textWe investigate the interfacial electronic structure of monolayer iron tetraphenylporphyrin chloride FeTPP Cl adsorbed on graphene Gr buffer layers supported by Ni 111 and Pt 111 . This study unveils the role of a graphene buffer layer in controlling the charge transfer mechanisms of self assembled porphyrins on metal surfaces, reshaping interfacial energy level alignment, charge transfer dynamics, interface dipoles, and charge injection barriers. By exploiting the intrinsic n and p type doping of graphene on Ni and Pt, we modulate the charge transfer behavior in iron tetraphenylporphyrin monolayers, using these systems as model platforms to probe interfacial electronic processes and the impact of graphene substrate coupling. Through a comprehensive multi technique approach, combining X ray photoemission, ultraviolet photoemission, and X ray absorption spectroscopies, we demonstrate how substrate induced doping drives significant changes at the molecule graphene metal interface. Core level binding energies BEs and ionization potentials IPs indicate weak physisorption in both systems, with opposite charge transfer directions depending on the substrate, despite similar molecular morphologies. On Gr Ni 111 , all core levels shift to higher BE, with a pronounced 0.6 eV shift in Fe 2p and a 0.15 eV IP increase, indicating electron transfer from the substrate to the molecule localized at the Fe center. On Gr Pt 111 , C 1s and N 1s shift to lower BE and the IP decreases by 0.15 eV, consistent with electron donation from the molecule to the substrate, more delocalized on the macrocycle. The small interface dipoles 0.15 eV for Ni, 0.25 eV for Pt and the absence of rigid shifts demonstrate that charge redistribution is fractional and site specific, governed primarily by electrostatics and graphene doping rather than strong hybridization. These findings suggest that the interaction strength and electronic behavior at the interface are governed by the underlying metal, with Gr acting as an effective electronic decoupler or mediator. Our study highlights the importance of the graphene metal interface in modulating charge transfer and level alignment in porphyrin based hybrid system
Extrusion based additive manufacturing of complex three dimensional ultra lightweight materials using the basidiomycete Fomes fomentarius
Get PDFFungal mycelium based materials harness the full potential of lignocellulosic resources in a sustainable way. Additive manufacturing can enhance design flexibility and reduce the use of plastic moulds in producing fungal mycelium based materials. Here, we explored additive manufacturing of living Fomes fomentarius for precise fabrication of fungal mycelium based materials. Using a 1.6 mm nozzle, we extruded a paste containing living fungal mycelium, rapeseed straw, and sodium alginate into various sizes and shapes. The aerial mycelium consisting of fungal hyphae that grow away from the substrate surface into the air formed was manually compressed during growth to maintain the desired shapes. For inactivation, freeze drying was found to maintain the original dimensions and shapes of the printed structures more effectively than convection oven drying. In addition to the printed composite materials, pure three dimensional fungal mycelium skins could also be produced. Electron scanning microscopy, Fourier transform infrared spectroscopy, X ray microtomography, hydrophobicity testing, compressive and tensile testing were used to investigate the morphological, physical and mechanical characteristics of the printed structures. Our results demonstrate that living F. fomentarius mycelium can be successfully used to manufacture lignocellulose fungal mycelium based materials with defined growth and hydrophobicity, which further expands its potential for future application as renewable biomaterials
Less pressure loss with extra packing The counterintuitive behavior of rotating packed beds
Get PDFThe Rotating Packed Bed RPB , as a process intensification unit in heat and mass transfer of multiphase processes, has been gaining growing attention in recent years as reflected in the numerous investigations of the device. However, many questions remain unanswered regarding the fluid dynamics in RPBs, including the counterintuitive behavior of higher dry pressure drop in operations with empty rotor compared to operations with packed rotor. To address this issue, we employ numerical methods to acquire a detailed description of the fluid flow inside the device. The metal foam as the packing material is resolved through reconstruction techniques found in the literature. The simulation results reveal that the absence of packing, due to conservation of angular momentum, induces higher local velocities and therefore higher pressure loss. Further, we derive fundamental mechanism of the pressure loss inside the RPB from the local data that can potentially enhance existing correlation
Light Induced Electronic Band Realignment at the Metal Halide Perovskite Monolayer MoS2 Heterojunction
Get PDFvan der Waals vdW heterojunctions offer many routes for advanced interface engineering toward superior optoelectronic functionality. To this end, the combination of 2D transition metal dichalcogenides TMDCs with metal halide perovskites has shown great potential for applications in photovoltaics and photodetectors. The electronic energy level alignment at such heterojunctions, i.e., the relative alignment of valence and conduction bands of the two materials, is crucial for their functionality, but its experimental determination is notoriously challenging. In this contribution, we determine the energy level alignment for the vdW heterojunction composed of monolayer molybdenum disulfide ML MoS2 and a triple cation mixed halide perovskite, enabled by surface cleaning by argon cluster sputtering. This effectively removes surface contaminants from the perovskite ML MoS2 stack without causing damage, enabling direct determination of the band alignment at the interface using ultraviolet and X ray photoelectron spectroscopy. Our results reveal a type II band alignment at the perovskite ML MoS2 interface. Importantly, the interfacial energy levels are not fixed once the heterojunction is formed, but the MoS2 energy levels shift relative to those of the perovskite under 1 sun illumination compared to the dark, by up to 0.25 eV. This energy level realignment, under conditions mimicking a photovoltaic device under operation, is attributed to photogenerated electron accumulation in the ML MoS2. Microscopic photoluminescence PL measurements reveal significant quenching of the perovskite PL signal in the heterojunction, confirming efficient charge transfer and the establishment of a type II heterojunction. These results demonstrate a living heterojunction energy landscape, opening up novel avenues for engineering perovskite TMDCs vdW heterojunctions for optoelectronic device
CspZ variant specific interaction with factor H incorporates a metal site to support Lyme borreliae complement evasion
No full textPolymorphic microbial immune evasion proteins dictate the pathogen species or strain specific virulence. Metals can impact how microbial proteins confer host pathogen interactions, but whether this activity can be allelically variable is unclear. Here, we investigate the polymorphic CspZ protein of Lyme disease spirochete bacteria to assess the role of metals in protein protein interaction. CspZ facilitates evasion of the complement system, the first line of immune defense through binding to the complement regulator factor H FH . By obtaining a high resolution cocrystal CspZ FH structure, we identified a zinc coordinating the binding of FH SCR6 7 domains to a Glu65 on a loop from CspZ of Borrelia burgdorferi B31. However, zinc is dispensable for human FH binding for CspZ orthologs with a different loop orientation and or lacking this glutamate. Phylogenetic analysis of all known human FH binding CspZ variants further grouped the proteins into three unique lineages correlating with loop sequences. This suggests multiple FH binding mechanisms evolved through Lyme disease spirochete host interactions. Overall, this multidisciplinary work elucidates how the allelically specific immune evasion role of metals is impacted by microbial protein polymorphism
Molecular Doping Induced Charge Transfer Complex Formation and Interfacial Dopant Interdiffusion on Graphite
Get PDFDoping is a powerful method to optimize the electrical characteristics of organic semiconductors, but a comprehensive picture capturing the phenomena at play is still under development. In this work, combining UV vis absorbance spectroscopy with ultraviolet and X ray photoelectron spectroscopy, we investigate the p type doping of sub monolayer films of two structurally isomeric organic semiconductors on graphite, naphtho[2,3 b]thieno [2 amp; 8244;,3 amp; 8244; 4 amp; 8243;,5 amp; 8243;]thieno[2 amp; 8243;,3 amp; 8243; 4 amp; 8242;,5 amp; 8242;]thieno[3 amp; 8242;,2 amp; 8242; b]naphtho[2,3 b]thiophene DN4T and naphtho[1,2 b]thieno[2 amp; 8244;,3 amp; 8244; 4 amp; 8243;,5 amp; 8243;]thieno[2 amp; 8243;,3 amp; 8243; 4 amp; 8242;,5 amp; 8242;]thieno[3 amp; 8242;,2 amp; 8242; b]naphtho[1,2b]thiophene isoDN4T , with the strong molecular acceptor 2,2 amp; 8242; perfluoronaphthalene 2,6 diylidene dimalononitrile F6TCNNQ . For DN4T, a hybrid highest occupied molecular level emerges from the hybridization of the DN4T and F6TCNNQ frontier occupied levels, resulting from the formation of DN4T F6TCNNQ charge transfer complexes. With increasing F6TCNNQ coverage, the electronic levels of both neutral DN4T and the DN4T F6TCNNQ complexes shift toward the Fermi level because of an interface dipole that is due to electron transfer from graphite to F6TCNNQ. In comparison, isoDN4T exhibits stronger interaction with F6TCNNQ and increased interfacial disorder, as evidenced by significant spectral broadening. These findings emphasize the profound impact of subtle structural variations on host dopant interactions and the importance of exploring multicomponent interfaces for advanced organic electronic and optoelectronic application
BaZrS3 Lights Up The Interplay of Electrons, Photons, and Phonons in Strongly Luminescent Single Crystals
Get PDFChalcogenide perovskites have emerged as a promising class of materials for the next generation of optoelectronic applications, with BaZrS amp; 8323; attracting signi amp; 64257;cant attention due to its wide bandgap, earth abundant composition, and thermal and chemical stability. However, previous studies have consistently reported weak and ambiguous photoluminescence PL , regardless of synthesis method, raising questions about the intrinsic optoelectronic quality of this compound. In this work, strong, band to band dominated PL is demonstrated at room temperature in high quality BaZrS amp; 8323; single crystals, with a PL quantum yield of amp; 8764;0.005 . Despite the narrow, single component PL emission band, time resolved PL measurements reveal a carrier lifetime of 1.0 0.2 ns. To understand the origin of the strong PL and short carrier lifetime, multiwavelength excitation and polarization dependent Raman measurements are performed, supported by amp; 64257;rst principles lattice dynamics calculations. All 23 theoretically predicted Raman active modes and their symmetries are identi amp; 64257;ed, providing a comprehensive reference for future studies. These results indicate that phonon assisted carrier decay and nontrivial electron phonon interactions contribute to the short carrier lifetimes, as evidenced by Raman spectroscopy and DFT calculations. Further studies on compositional variations or partial cation anion substitutions can mitigate electron phonon coupling and enhance carrier lifetimes. By establishing a detailed reference for the intrinsic vibrational and optoelectronic properties of BaZrS amp; 8323;, this work paves the way for further advancements in chalcogenide perovskites for energy and optoelectronic technologie
Impact of acid etching on surfaces and near surface region in nitrogen plasma terminated polycrystalline diamond
Get PDFIn this study, the influence of tri acid HClO4 H2SO4 HNO3 1 3 4 etching on the surface and near surface chemical properties of radio frequency RF nitrogen plasma terminated polycrystalline diamond PCD surfaces is reported. From the C 1s and N 1s high resolution X ray photoelectron spectroscopy HR XPS measured as a function of photon energy, it is clearly shown that acid etching reduced the thickness of the disordered C sp2 layer created by the nitrogen plasma treatment exposing an upper surface of a larger C sp3 character alongside the formation of C Ox bonds. This is accompanied by a reduction in the nitrogen surface concentration and the N 1s XP peak full width at half maximum FWHM , suggesting a more homogeneous nitrogen bonding to the diamond surface. High resolution electron energy loss spectroscopy HREELS shows that NH ads species produced by the plasma processes are preferentially etched alongside the formation of C O ads , C O ads , and COOC ads species, whereas hydrogen is bonded in various CHy ads configurations. The C K edge NEXAFS spectra show characteristic peaks in the pre edge structure clearly associated with nitrogen bonding. Following acid etching, the intensities of peaks related to defect states are reduced, whereas the diamond second band gap at 302.4 eV increases in intensity. N K edge NEXAFS of the nitrogen plasma terminated surfaces show peaks associated to C N ads and C N ads bonding, which acid etching results in the preferred depopulation of C N ads bond