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Effect of Extensional Flow on the Evaporative Assembly of a Donor–Acceptor Semiconducting Polymer
The ability to deposit polymer semiconductors (PSCs) over a large area at near-ambient conditions makes them exciting candidates for low-cost, large-area electronic applications. Given the sensitivity of the charge carrier mobility in PSCs to the nature of their deposition from solution, a mechanistic understanding of deposition processes is essential for enhancing and controlling a PSC’s electrical performance. Polymer chain alignment has been largely posited as a strategy for improving the electrical performance of PSCs. Herein, the ability of a micropillar shearing blade to align polymer chains of poly(2,5-bis(2-octyldodecyl)-3,6-di(thiophen-2-yl)diketopyrrolo[3,4-c]pyrrole-1,4-dione-alt-thieno[3,2-b]thiophen) (DPP-TT) during solution shearing by increasing extensional flow is investigated. A sufficiently strong extensional flow field is found to be capable of aligning polymer chains and inducing crystallization. Such an alignment of crystallite domains is observed to be correlated to increased charge carrier mobility, but the effect of alignment on charge transport is dependent on deposition conditions. Furthermore, the ability of polymer chains to be aligned by using extensional flow, and the effect of alignment on subsequent charge transport, is highly dependent on polymer chain length due to changes in both solution state properties and charge transport mechanisms.
Evidence of Stratification in Binary Colloidal Films from Microbeam X-ray Scattering: Toward Optimizing the Evaporative Assembly Processes for Coatings
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Dual-source evaporation of silver bismuth iodide films for planar junction solar cells
Non-toxic and air-stable silver bismuth iodide semiconductors are promising light absorber candidates for photovoltaic applications owing to a suitable band gap for multi- or single-junction solar cells. Recently, solution-based film fabrication approaches for several silver bismuth iodide stoichiometries have been investigated. The current work reports on a facile and reproducible two-step coevaporation/annealing approach to deposit compact and pinhole-free films of AgBi 2 I 7 , AgBiI 4 and Ag 2 BiI 5 . X-ray diffraction (XRD) in combination with scanning electron microscopy (SEM)/energy-dispersive X-ray spectroscopy (EDX) analysis reveals formation of pure cubic (Fd$\bar{3}$m) with combining macron]m) phase AgBi 2 I 7 , cubic (Fd$\bar{3}$m) or rhombohedra (R$\bar{3}$m with combining macron]m) phase AgBiI 4 , each with >3 μm average grain size, or the rhombohedral phase (R$\bar{3}$m) Ag 2 BiI 5 with >200 nm average grain size. A phase transition from rhombohedral to cubic structure is investigated via temperature-dependent X-ray diffraction (TD-XRD). Planar-junction photovoltaic (PV) devices are prepared based on the coevaporated rhombohedral AgBiI 4 films, with titanium dioxide (TiO 2 ) and poly(3-hexylthiophene) (P3HT) as electron- and hole-transport layers, respectively. Finally, the best-performing device exhibited a power conversion efficiency (PCE) of as high as 0.9% with open-circuit voltage (VOC) > 0.8 V in the reverse scan direction (with significant hysteresis).
Secondary organic aerosol formation from evaporated biofuels: comparison to gasoline and correction for vapor wall losses
With an ongoing interest in displacing petroleum-based sources of energy with biofuels, we measure and model the formation and composition of secondary organic aerosol (SOA) from organic compounds present in biofuels.
Evaporated organic–MoO 3 composite hole transport layers toward stable perovskite solar cells
The release and diffusion of corrosive iodine species limit perovskite solar cell (PSC) stability. An organic-MoO 3 composite hole transport layer (HTL) with enhanced thermal stability is devised to suppress iodine diffusion and improve PSC stability.
Analysis of antifoam agent degradation products in an evaporator
A wetting agent used to control foaming in the Chemical Processing Cell at the Defense Waste Processing Facility degrades to form compounds that could volatilize to form vapor exceeding the lower flammability limit. Three identified components of concern were hexamethyl disiloxane, trimethyl silanol, and propanal. Analytical methods were developed and implemented on a real waste sample to monitor degradation products. In this work, using standards, an extraction method with dichloromethane and analysis by gas chromatography-mass spectrometry and hydrogen nuclear magnetic resonance was developed. Both methods had detection limits less than 1 mg/L for the analytes.
Effects of radiation pressure on the evaporative wind of HD 209458b
ABSTRACT The role of radiation pressure in shaping exoplanet photoevaporation remains a topic of contention. Radiation pressure from the exoplanet’s host star has been proposed as a mechanism to drive the escaping atmosphere into a ‘cometary’ tail and explain the high velocities observed in systems where mass-loss is occurring. In this paper, we present results from high-resolution 3D hydrodynamic simulations of a planet similar to HD 209458b. We self-consistently launch a wind flowing outwards from the planet by calculating the ionization and heating resulting from incident high-energy radiation, and account for radiation pressure. We first present a simplified calculation, setting a limit on the Lyman-α flux required to drive the photoevaporated planetary material to larger radii and line-of-sight velocities. We then present the results of our simulations, which confirm the limits determined by our analytic calculation. We thus demonstrate that, within the limits of our hydrodynamic simulation and for the Lyman-α fluxes expected for HD 209458, radiation pressure is unlikely to significantly affect photoevaporative winds or to explain the high velocities at which wind material is observed, though further possibilities remain to be investigated.
Effects of charge exchange on the evaporative wind of HD 209458b
ABSTRACT The role of charge exchange in shaping exoplanet photoevaporation remains a topic of contention. Exchange of electrons between stellar wind protons from the exoplanet’s host star and neutral hydrogen from the planet’s wind has been proposed as a mechanism to create ‘energetic neutral atoms’ (ENAs), which could explain the high absorption line velocities observed in systems where mass-loss is occurring. In this paper, we present results from three-dimensional hydrodynamic simulations of the mass-loss of a planet similar to HD 209458b. We self-consistently launch a planetary wind by calculating the ionization and heating resulting from incident high-energy radiation, inject a stellar wind into the simulation, and allow electron exchange between the stellar and planetary winds. We predict the potential production of ENAs by the wind–wind interaction analytically, and then present the results of our simulations, which confirm the analytic limits. Within the limits of our hydrodynamic simulation, we find that charge exchange with the stellar wind properties examined here is unable to explain the absorption observed at high Doppler velocities.
Evaporating the Milky Way halo and its satellites with inelastic self-interacting dark matter
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Quarkonium polarization in Pb + Pb collisions in the improved color evaporation model
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Level densities for Ga 69 , 71 nuclei using a particle-evaporation technique
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Quantum evaporation of classical breathers
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Ensemble from coarse graining: Reconstructing the interior of an evaporating black hole
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