Effect of Bromine Substitution on the Ion Migration and Optical Absorption in MAPbI₃ Perovskite Solar Cells: The First-Principles Study

In the past few years, the remarkable energy conversion efficiency of lead-halide-based perovskite solar cells (PSCs) has drawn extraordinary attention. However, some exposed problems in PSCs such as the low chemical stability and so forth are tough to eliminate. A fundamental understanding of ionic transport at the nanoscale is essential for developing high-performance PSCs based on the anomalous hysteresis current–voltage (<i>I</i>–<i>V</i>) curves and the poor stability. Our work is to understand the ionic transport mechanism by introducing suitable halogen substitution with insignificant impact on light absorption to hinder ion diffusion and thereby to seek a method to improve the stability. Herein, we used first-principles density functional theory (DFT) to calculate the band gaps and the optical absorption coefficients, and the interstitial and the vacancy defect diffusion barriers of halide in the orthogonal phase MAPbX₃ (MA = CH₃NH₃, X = I, Br, I_0.5Br_0.5) perovskite, respectively. The research results show that a half bromine substitution not only prevents ion migration in perovskite, but also maintains a favorable light absorption capacity. It may be helpful to maintain the PSC’s property of light absorption with a similar atomic substitution. Furthermore, smaller atomic substitution for the halogen atoms may be essential for increasing the diffusion barrier

First-Principles Screening and Design of Novel Triphenylamine-Based D−π–A Organic Dyes for Highly Efficient Dye-Sensitized Solar Cells

We screen a series of π-conjugated bridge groups and design a range of metal-free organic donor−π–acceptor (D−π–A) <b>SPL101</b>–<b>SPL108</b> dyes based on the experimentally synthesized <b>C217</b> dye for highly efficient dye-sensitized solar cells (DSSC) using density functional theory (DFT) and time-dependent DFT (TDDFT), and further calculate their physical and electronic properties, including geometrical structures, electronic cloud distribution, molecular orbital energy levels, absorption spectra, light harvesting efficiency (LHE), driving force of injection (Δ<i>G</i>_inj) and regeneration (Δ<i>G</i>_reg), and electron dipole moment (μ_normal). Results reveal that the π-conjugated bridge groups in <b>SPL103</b> and <b>SPL104</b> are promising functional groups for D−π–A organic dyes. In particular,<b> SPL106 </b>and<b> SPL108</b> have not only smaller energy gaps, higher molar extinction coefficients, and 128 and 143 nm redshifts, but also a broader absorption spectrum covering the entire visible range up to the near-IR region of 1200 nm compared to <b>C217</b> dye

Rational Design of Dithienopicenocarbazole-Based Dyes and a Prediction of Their Energy-Conversion Efficiency Characteristics for Dye-Sensitized Solar Cells

A series of metal-free organic donor–acceptor (D–A) derivatives (<b>ME01</b>–<b>ME06</b>) of the known dye <b>C281</b> were designed using first-principles calculations in order to evaluate their potential for applications in dye-sensitized solar cells (DSSCs). Their physical and electronic properties were calculated using density functional theory (DFT) and time-dependent density functional theory (TD-DFT). These include molecular properties that are required to assess the feasibility of a dye to function in DSSCs: UV–vis absorption spectra, light-harvesting efficiency (LHE), and driving forces of electron injection (<i>Δ<i>G</i></i>_inj). <b>ME01</b>, <b>ME02</b>, and <b>ME04</b> are predicted to exhibit broad absorption optical spectra that cover the entire visible range, rendering these three dyes promising DSSC prospects. Device-relevant calculations on these three short-listed dyes and the parent dye <b>C281</b> were then performed, whereupon the dye molecules were adsorbed onto anatase TiO₂ surfaces to form the DSSC working electrode. Associated DSSC device characteristics of this dye···TiO₂ interfacial structure were determined. These include the light-harvesting efficiency, the number of injected electrons, the electron-injection lifetime, and the quantum-energy alignment of the adsorbed dye molecule to that of its device components. In turn, these calculated parameters enabled the derivation of the DSSC device performance parameters: short-circuit current density, <i>J</i>_SC, incident photon-to-electron conversion efficiency, IPCE, and open-circuit voltage, <i>V</i>_OC. Thus, we demonstrate a systematic <i>ab initio</i> approach to screen rationally designed D–A dyes with respect to their potential applicability in high-performance DSSC devices

Image_1_The effect of weighted blankets on sleep and related disorders: a brief review.pdf

BackgroundSleep disorders such as insomnia can lead to a range of health problems. The high risk of side effects and drug abuse of traditional pharmacotherapy calls for a safer non-pharmacotherapy.AimsTo examine the use and efficacy of weighted blankets in improving sleep and related disorders in different populations and explore the possible mechanisms.MethodsA literature search was conducted using PubMed, Embase, Web of Science, MEDLINE, Cochrane Library and CNKI databases. Eligible studies included an intervention with weighted blankets and outcomes covering sleep and/or related disorders (behavioral disturbance, negative emotions and daytime symptoms). Studies using other deep pressure, compression, or exercise-related interventions were excluded.ConclusionsMost of the included studies showed that weighted blankets could effectively improve sleep quality and alleviate negative emotions and daytime symptoms in patients with sleep disorders, attention deficit hyperactivity disorder, autism spectrum disorder, and other related disorders, with a possible mechanism of deep pressure touch.RecommendationsWeighted blankets might be a promising tool for sleep interventions among individuals with sleep disorders in clinical settings. More high-quality and large-scale randomized controlled trials are needed to further validate the safety and efficacy of weighted blankets and explore precise mechanisms.</p