at the surface and grain boundaries, acting as carrier recombination centers and greatly limiting the open-circuit voltage (V oc ) of PSCs. Meanwhile, these trap states can lead to the infiltration of moisture and oxygen into perovskite, and subsequently harm the device stability in ambient environment. [23][24][25][26] These trap states at the surface and grain boundaries are most likely induced by ions migration, oxidization of I − or evaporation of methylammonium iodide (MAI), which are mainly manifested as under-coordinated metal cations or halide anions. [27][28][29] So far, a variety of passivation materials (also known as passivator) have been added into perovskite films to induce defect passivation through forming coordination with under-coordinated metal cations or halide anions. For instance, phenyl-C61-butyric acid methyl ester (PCBM), as a Lewis acid could passivate the trap states by forming coordination with halide ions and thus eliminate the notorious photocurrent hysteresis. [28,30] On the contrary, Snaith and co-workers demonstrated that Lewis base molecules, such as thiophene or pyridine, could heal the trap states by forming coordination with under-coordinated Pb 2+ ions in perovskite films. [31] Since these initial results of defect passivation by reducing the uncoordinated ions in perovskite layer is proven to be effective, a defect passivator in perovskite layer should have more room for improvement. For example, a well-designed passivator in the perovskite layer should take the defect coordination and device air stability into consideration simultaneously. Thus, more effort is required to understand how to choose a suitable passivator in the perovskite layer.Among the large selection of functional groups, carboxyl (COOH) has been effectively used in other photovoltaic device as an indispensable anchoring group due to the strong coordination with metal oxide. [32] In the case of perovskite films, COOH is also found to have the interaction with perovskite films. [33,34] Small molecules such as amino acids, [35] acetate acids [8] were used to crosslink the perovskite boundaries or assist the crystallization process. However, the effect of charge recombination which is critical for the device performance is rarely mentioned in the previous work. It may because of small molecules were used as small amount of additives in the perovskite film which randomly distributed among the crystal boundaries. As the defects of perovskite film mainly locate at the top surface, [28] the controlling of stereochemical configuration is required for the film surface passivation.Organic-inorganic halide perovskites are efficient absorbers for solar cells. Nevertheless, the trap states at the surfaces and grain boundaries are a detri mental factor compromising the device performance. Here, an organic dye (AQ310) is employed as passivator to reduce the trap states of the perovs kites and promote better stability. The results demonstrate that the trap states of perovskite are minimized by the presence of AQ310's CO...
We discuss the motion of a triple line for a fluid spreading on a flat solid surface in conditions of partial wetting: the equilibrium contact angle θe is assumed to be finite but small: 0 < θe [Lt ] 1. We distinguish four regions: (1) a molecular domain of size a (≈ a few Ångströms) very near the triple line, where the continuum description breaks down; (2) a proximal region (of length a/θ2e and height a/θe) where the long-range Van der Waals forces dominate; (3) a central region, where capillary forces and Poiseuille friction are the only important ingredients; (4) a distal region where macroscopic features (related to the size of the droplet, or to gravitational forces) come into play. In regions (2, 3, 4) the flow may be described in a lubrication approximation, and with a linearized form of the capillary forces. We restrict our attention to low capillary numbers Ca and expand the profiles to first order in Ca near the static solution. The main results are: (a) the logarithmic singularity which would have occurred in a simple wedge picture is truncated by the long-range forces, at a fluid thickness a/θe. This effect is more important, at small θe, than the effects of slippage which have often been proposed to remove the singularity, and which would lead to a truncation thickness comparable with the molecular size a; (b) in the central region, the local slope θ(x) grows logarithmically with the distance x from the triple line; (c) one can match explicitly the solutions in the central and distal region: we do this for one specific example: a plate plunging into a fluid with an incidence angle exactly equal to θe. In this case we show that, far inside the distal region, the perturbation of the slope decays like 1/x2.
A portable vacuum interface allowing direct probing of the electrode-electrolyte interface was developed. A classical electrochemical system consisting of a gold working electrode, platinum counter electrode, platinum reference electrode, and potassium iodide electrolyte was used to demonstrate real-time observation of the gold iodide adlayer on the electrode and chemical species as a result of redox reactions using cyclic voltammetry (CV) and time-of-flight secondary ion mass spectrometry (ToF-SIMS, a vacuum-based surface technique) simultaneously. This microfluidic electrochemical probe provides a new way to investigate the surface region with adsorbed molecules and the region of the diffused layer with chemical speciation in liquids in situ by surface sensitive techniques.
The transport of hydrated ions across nanochannels is central to biological systems and membrane-based applications, yet little is known about their hydrated structure during transport due to the absence of in situ characterization techniques. Herein, we report experimentally resolved ion dehydration during transmembrane transport using modified in situ liquid ToF-SIMS in combination with MD simulations for a mechanistic reasoning. Notably, complete dehydration was not necessary for transport to occur across membranes with sub-nanometer pores. Partial shedding of water molecules from ion solvation shells, observed as a decrease in the average hydration number, allowed the alkali-metal ions studied here (lithium, sodium, and potassium) to permeate membranes with pores smaller than their solvated size. We find that ions generally cannot hold more than two water molecules during this sterically limited transport. In nanopores larger than the size of the solvation shell, we show that ionic mobility governs the ion hydration number distribution. Viscous effects, such as interactions with carboxyl groups inside the membrane, preferentially hinder the transport of the mono-and dihydrates. Our novel technique for studying ion solvation in situ represents a significant technological leap for the nanofluidics field and may enable important advances in ion separation, biosensing, and battery applications.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
customersupport@researchsolutions.com
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
This site is protected by reCAPTCHA and the Google Privacy Policy and Terms of Service apply.
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.