Twenty Little Studies

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Knowledge is power: A theory of information, income and welfare spending

No voters cast their votes based on perfect information, but better educated and richer voters are on average better informed than others. We develop a model where the voting mistakes resulting from low political knowledge reduce the weight of poor voters, and cause parties to choose political platforms that are better aligned with the preferences of rich voters. In US election survey data, we find that income is more important in affecting voting behavior for more informed voters than for less informed voters, as predicted by the model. Further, in a panel of US states we find that when there is a strong correlation between income and political information, Congress representatives vote more conservatively, which is also in line with our theory.Political Economics

Exploring the Early Time Behavior of the Excited States of an Archetype Thermally Activated Delayed Fluorescence Molecule

Optical pump–probe techniques allow for an in-depth study of dark excited states. Here, we utilize them to map and gain insights into the excited states involved in the thermally activated delayed fluorescence (TADF) mechanism of a benchmark TADF emitter DMAC-TRZ. The results identify different electronic excited states involved in the key TADF transitions and their nature by combining pump–probe and photoluminescence measurements. The photoinduced absorption signals are highly dependent on polarity, affecting the transition oscillator strength but not their relative energy positions. In methylcyclohexane, a strong and vibronically structured local triplet excited state absorption (3LE → 3LE n ) is observed, which is quenched in higher polarity solvents as 3CT becomes the lowest triplet state. Furthermore, ultrafast transient absorption (fsTA) confirms the presence of two stable conformers of DMAC-TRZ: (1) quasi-axial (QA) interconverting within 20 ps into (2) quasi-equatorial (QE) in the excited state. Moreover, fsTA highlights how sensitive excited state couplings are to the environment and the molecular conformation

Real building implementation of a deep reinforcement learning controller to enhance energy efficiency and indoor temperature control

Deep Reinforcement Learning (DRL) has emerged as a promising approach to address the trade-off between energy efficiency and indoor comfort in buildings, potentially outperforming conventional Rule-Based Controllers (RBC). This paper explores the real-world application of a Soft-Actor Critic (SAC) DRL controller in a building’s Thermally Activated Building System (TABS), focusing on optimising energy consumption and maintaining comfortable indoor temperatures. Our approach involves pre-training the DRL agent using a simplified Resistance-Capacitance (RC) model calibrated with real building data. The study first benchmarks the DRL controller against three RBCs, two Proportional-Integral (PI) controllers and a Model Predictive Controller (MPC) in a simulated environment. In the simulation study, DRL reduces energy consumption by 15% to 50% and decreases temperature violations by 25% compared to RBCs, reducing also energy consumption and temperature violations compared to PI controllers by respectively 23% and 5%. Moreover, DRL achieves comparable performance in terms of temperature control but consuming 29% more energy than an ideal MPC. When implemented in a real building during a two-month cooling season, the DRL controller performances were compared with those of the best-performing RBC, enhancing indoor temperature control by 68% without increasing energy consumption. This research demonstrates an effective strategy for training and deploying DRL controllers in real building energy systems, highlighting the potential of DRL in practical energy management applications

A deep blue B,N-doped heptacene emitter that shows both thermally activated delayed fluorescence and delayed fluorescence by triplet-triplet annihilation

Authors thank the Leverhulme Trust (RPG-2016-047). This project has received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska Curie grant agreement No 838885 (NarrowbandSSL) and 812872 (TADFlife). We thank Umicore for their generous supply of catalysts. S.S. acknowledges support from the Marie Skłodowska-Curie Individual Fellowship. SB acknowledges support from the Bayrisches Staatsministerium für Wissenschaft und Kunst (Stmwk) in the framework of the initiative "SolTech", as well as from the German Science foundation (DFG) (No. 392306670). Computational resources have been provided by the Consortium des Équipements de Calcul Intensif (CÉCI), funded by the Fonds de la Recherche Scientifiques de Belgique (F.R.S.-FNRS) under Grant No. 2.5020.11, as well as the Tier-1 supercomputer of the Fédération Wallonie-Bruxelles, infrastructure funded by the Walloon Region under the grant agreement n111754.An easy-to-access, near-UV-emitting linearly extended B,N-doped heptacene with high thermal stability is designed and synthesized in good yields. This compound exhibits thermally activated delayed fluorescence (TADF) at ambient temperature from a multiresonant (MR) state and represents a rare example of a non-triangulene-based MR-TADF emitter. At lower temperatures triplet–triplet annihilation dominates. The compound simultaneously possesses narrow, deep-blue emission with CIE coordinates of (0.17, 0.01). While delayed fluorescence results mainly from triplet–triplet annihilation at lower temperatures in THF solution, where aggregates form upon cooling, the TADF mechanism takes over around room temperature in solution when the aggregates dissolve or when the compound is well dispersed in a solid matrix. The potential of our molecular design to trigger TADF in larger acenes is demonstrated through the accurate prediction of ΔEST using correlated wave-function-based calculations. On the basis of these calculations, we predicted dramatically different optoelectronic behavior in terms of both ΔEST and the optical energy gap of two constitutional isomers where only the boron and nitrogen positions change. A comprehensive structural, optoelectronic, and theoretical investigation is presented. In addition, the ability of the achiral molecule to assemble on a Au(111) surface to a highly ordered layer composed of enantiomorphic domains of racemic entities is demonstrated by scanning tunneling microscopy.PostprintPeer reviewe

Improving processability and efficiency of Resonant TADF emitters : a design strategy

This work is funded by the EC through the Horizon 2020 Marie Sklodowska-Curie ITN project TADFlife. The St Andrews team would also like to thank the Leverhulme Trust (RPG-2016- 047) and EPSRC (EP/P010482/1) for financial support. Computational resources have been provided by the Consortium des Équipements de Calcul Intensif (CÉCI), funded by the Fonds de la Recherche Scientifiques de Belgique (F.R.S.-FNRS) under Grant No. 2.5020.11, as well as the Tier-1 supercomputer of the Fédération Wallonie-Bruxelles, infrastructure funded by the Walloon Region under the grant agreement n1117545. AP acknowledges the financial support from the Marie Curie Fellowship (MILORD project, N°. 748042). DB is a FNRS Research Director. We thank Franck-Julian Kahle for support with data analysis.A new design strategy is introduced to address a persistent weakness with resonance thermally activated delayed fluorescence (R-TADF) emitters to reduce aggregation-caused quenching effects, which we identify as one of the key limiting factors. The emitter Mes3DiKTa shows an improved photoluminescence quantum yield of 80% compared to 75% for the reference DiKTa in 3.5 wt% mCP. Importantly, emission from aggregates, even at high doping concentrations, is eliminated and aggregation-caused quenching is strongly curtailed. For both molecules, triplets are almost quantitatively upconverted into singlets in electroluminescence, despite a significant (~0.21 eV) singlet-triplet energy gap (ΔEST), in line with correlated quantum-chemical calculations, and a slow reverse intersystem crossing. We speculate that the lattice stiffness responsible for the narrow fluorescence and phosphorescence emission spectra also protects the triplets against non-radiative decay. An improved EQEmax of 21.1% for Mes3DIKTa compared to the parent DiKTa (14.7%) and, importantly, reduced efficiency roll- off compared to literature resonance TADF OLEDs, shows the promise of this design strategy for future design of R-TADF emitters for OLED applications.Publisher PDFPeer reviewe