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Hydrated electrons are anionic species that are formed when an excess electron is introduced into liquid water. Building an understanding of how hydrated electrons behave in solution has been a long-standing effort of simulation methods, of which density functional theory (DFT) has come to the fore in recent years. The ability of DFT to model the reactive chemistry of hydrated electrons is an attractive advantage over semi-classical methodologies; however, relatively few density functional approximations (DFAs) have been used for the hydrated electron simulations presented in the literature. Here, we simulate hydrated electron systems using a series of exchange–correlation (XC) functionals spanning Jacob’s ladder. We calculate a variety of experimental and other observables of the hydrated electron and compare the XC functional dependence for each quantity. We find that the formation of a stable localized hydrated electron is not necessarily limited to hybrid XC functionals and that some hybrid functionals produce delocalized hydrated electrons or electrons that react with the surrounding water at an unphysically fast rate. We further characterize how different DFAs impact the solvent structure and predicted spectroscopy of the hydrated electron, considering several methods for calculating the hydrated electron’s absorption spectrum for the best comparison between structures generated using different density functionals. None of the dozen or so DFAs that we investigated are able to correctly predict the hydrated electron’s spectroscopy, vertical detachment energy, or molar solvation volume. 

Abstract Semiconducting polymers are of interest due to their solution processibility and broad electronic applications. Electrochemistry allows these wide bandgap semiconductors to be converted to conducting polymers by doping such polymers at various potentials. When polymers arep‐doped to improve their conductivity via electrochemical oxidation, various positively‐charged carriers are created, including polarons (singly‐charged) and bipolarons (doubly‐charged). Carrier creation is accompanied by anion intercalation from the electrolyte for charge balance, and this insertion requires ion mobility. In this work, poly(3‐hexylthiophene) (P3HT) with different regioregularities is used to understand the relationship between solvent swelling, which affects anion intercalation, and electrochemical doping. Cyclic voltammetry, optical absorption spectroscopy, and grazing incidence wide‐angle X‐ray scattering (GIWAXS) measurements are used to correlate the doping level with structural changes. In situ electrochemical quartz crystal microbalance (EQCM) measurements are used to quantify the swelling of the polymers dynamically during electrochemical cycling. Lastly, in situ conductivity measurements are done to measure the effect of swelling on the ionic and electronic conductivity. The results indicate that solvent swelling is required for bipolaron formation, and that swelling facilitates both the small structural changes need for polaron formation and the disordering required for bipolaron formation. 

To improve their electrical conductivity for various applications, semiconducting polymer films are often chemically doped to increase their equilibrium charge carrier density. Recently, a novel doping method involving anion exchange has provided control over the identity of the counterions that reside in such films, leading to increased stability under ambient conditions. In this work, however, we show that by ion-exchanging 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane-doped poly(3-hexylthiophene-2,5-diyl) films with hygroscopic salts like bis(trifluoromethane)sulfonimide lithium or LiPF6, the doped film's electrical conductivity drops significantly when exposed to ambient humidity. The change in electrical conductivity depends directly on the degree of hygroscopicity of the counterion and can be over 50% with relatively modest changes in relative humidity (RH), and up to a factor of four between ambient and completely dry conditions. The film's humidity response is entirely reversible when adsorbed water is removed, potentially allowing the doped semiconducting polymer films to function as humidity sensors. Hall effect measurements show that the cause of the drop in conductivity with increasing RH is due to a decrease in carrier mobility and not due to de-doping. Our results emphasize that it is important to control the sample environment when making electrical measurements on anion-exchange doped semiconducting polymer films. 

We report a comparative study of the well-known fluorophore 9,10-diphenylanthracene with a synthetic aza analog. OLED devices were prepared and showed that nitrogen atom incorporation leads to an unexpected red shift in electroluminescence.