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Tuning Optoelectronic Properties of Dithienopyrrole Donor Molecules for Organic Solar Cells
摘要： Theoretical analysis of physical properties of organic solar cells (OSCs) are important in order to reveal the correlation between power conversion efficiencies (PCE), structure and properties. Five new A?D?A type small molecules M1, M2, M3, M4, and M5 were designed by using dithienopyrrole (DTP) as electron rich donor unit with different types of π-spacers and end capped acceptor units. Functional MPW1PW91/6-31G(d,p) level of theory was used to optimize the geometry of all molecules. For excited state calculation TD-MPW1PW91/6-31G(d,p) level of theory was used. The geometries, electronic structures, dipole moment, open circuit voltage, reorganization energies and charge transport properties of designed molecules (M1 M5) have been scrutinized comparing with the reported compound R. The results revealed that the HOMO energy levels of molecules M1, M2, M3, and M5 were lower while M4 was of high energy level thus facilitate the donation of electron as compared to references molecule R. While LUMO energy level of all the molecules were slightly high energy due electron withdrawing effects of spacer and acceptor moiety. Highest energy gap of HOMO–LUMO was observed in M1 which was 2.48 eV and M3 showed low energy gap (2.11 eV) as compared to other designed molecules. All molecules showed low values for λe, so they have high rate of electron transfer as compared to R. All designed molecules exhibited higher value of dipole moment as compared to reference molecule R except M1. Higher value of dipole moment of donor molecules contrary to reference means good solubility towards organic solvents which is beneficial for further solar cell device fabrication. All designed molecules show higher Voc values except M4 which has comparable Voc with respect to reference molecule R. In short, choice of appropriate electron withdrawing and donating groups is very important for improving power conversion efficiencies of OSCs.
关键词： Dithienopyrrole,reorganization energy,open circuit voltages,density of states,density functional theory
更新于2025-09-12 10:27:22
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Interfacial Engineering through Chloride-Functionalized Self-Assembled Monolayers for High-Performance Perovskite Solar Cells
摘要： The family of organic-inorganic hybrid perovskite (OIHPs) materials is one of the most promising for very high efficiency photovoltaic solar cells application. In the present work, the effect of a series of self-assembled monolayers placed at the TiO2-perovskite junction, on the functioning of triple cation perovskite solar cells has been investigated. We show that employing 4-chlorobenzoic acid leads to the marked boosting of the solar cells performances. The starting pristine cell had a 20.3% power conversion efficiency (PCE) and the chemical engineering permitted to reach a PCE up to 21.35%. Our experimental study completed by density functional theory (DFT) calculations and modelling show that this improvement is due to the reduction of interfacial states, to the improvement of the quality of the OIHP material and to the structural continuity between TiO2 and the OIHP. Especially, we demonstrate that the interfacial chemical interactions are important to consider in the design of highly efficient devices.
关键词： Perovskite solar cells,Self-assembled monolayers,Hydrides,Benzoic acid derivatives,High efficiency,Density functional theory
更新于2025-09-12 10:27:22
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Stable Triple Cation Perovskite Precursor for Highly Efficient Perovskite Solar Cells Enabled by Interaction with 18C6 Stabilizer
摘要： Triple cation perovskites (Cs0.05(MA0.17FA0.83)0.95Pb(I0.83Br0.17)3) have received lots of attention owing to the excellent stability and photovoltaic performance. However, the development toward efficient solar cells has been significantly impeded by its intrinsic precursor instability, as well as defective crystal surface. Herein, a strategy for introducing the additive of 1,4,7,10,13,16-hexaoxacyclooctadecane (18C6) in the precursor solution, rendering an excellent stability of more than one month, and the defect passivation effect on the crystal surface are demonstrated. In those perovskite solar cells, a power conversion efficiency of 20.73% has been achieved with a substantially improved open-circuit voltage and fill factor. As evidenced by the density functional theory calculations, the fundamental reason relating to the enhanced performance is found to be the interaction effect between the 18C6 and cations, and in particular the formation of the 18C6/Pb complex. This finding represents an alternative strategy for achieving a stable precursor solution and efficient perovskite solar cells.
关键词： 18-crown-6,passivation,precursor stability,density functional theory
更新于2025-09-12 10:27:22
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N719 Derivatives for Application in a Dye-Sensitized Solar Cell (DSSC): A Theoretical Study
摘要： The primary goal of this investigation is to analyze the influence of the chemical modifications on the electronic structures of N719 derivatives for their use in Dye-Sensitized Solar Cells (DSSC), by employing Density Functional Theory (DFT). UV-Visible spectra indicate that the electronic configurations are essential to study the absorption of solar irradiation and to analyze the charge transport mechanism between the Electron Transport Layer (ETL), the electrolyte, and the dye. Open and closed-shell electronic configurations are related to the absorption and the excitation energies of the dye. According to the results reported here, it is possible to say that the best candidates are N719, N719-2, N719-7, and N719-8 (neutral and di-anionic). They may be used as useful dye sensitizers due to their bandgap and band alignment with the ETL, which contributes to having an effective charge transport during the functioning of the solar device. Another parameter that is reported in this investigation is the Light-Harvesting Efficiency (LHE) for all studied systems. This could help to improve the performance of the device since there is an increment in the generation of charge carriers. These results could be useful as a guide for experimental investigations on chemical modifications of these sensitizers.
关键词： UV-Visible Spectra,Light-Harvesting Efficiency,Molecular Structure,Spectroscopy,DFT,N719 Derivatives,Theoretical Study,Quantum Chemistry,Density Functional Theory,DSSC,Dye-Sensitized Solar Cell,LHE
更新于2025-09-12 10:27:22
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<i>Ab initio</i> study of temperature- and laser-induced phase transitions in
摘要： We analyze the bulk phase transitions of the three titanium dioxide polymorphs anatase, rutile, and brookite in thermodynamical equilibrium and after ultrafast laser excitation using the generalized solid-state nudged elastic band (G-SSNEB) method. For calculating the forces and stresses needed for G-SSNEB, we use electronic-temperature dependent density functional theory calculations. Our results show that the anatase-rutile and brookite-rutile phase transitions have a considerably lower energy barrier than the anatase-brookite phase transition in the thermodynamical equilibrium and upon laser excitation. The obtained transition temperatures in thermodynamical equilibrium are consistent with experimentally observed ones. Furthermore, our calculations show that the pathways of the phase transition are not affected considerably by the applied laser pulse. Although the pathways do not change considerably we see that the rutile phase is stabilized by the laser pulse.
关键词： phase transitions,density functional theory,G-SSNEB method,titanium dioxide,laser excitation
更新于2025-09-12 10:27:22
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Two-dimensional hydrogenated buckled gallium arsenide: An <i>ab-initio</i> study
摘要： First-principles calculations have been carried out to investigate the stability, structural and electronic properties of two?dimensional hydrogenated GaAs with three possible geometries: chair, zigzag?line and boat con?gurations. The e?ect of van der Waals interactions on 2D H?GaAs systems has also been studied. These con?gurations were found to be energetic and dynamic stable, as well as having a semiconducting character. Although two?dimensional GaAs adsorbed with H tends to form a zigzag?line con?guration, the energy di?erences between chair, zigzag?line and boat are very small which implies the metastability of the system. Chair and boat con?gurations display a Γ?Γ direct bandgap nature, while pristine 2D?GaAs and zigzag?line are indirect semiconductors. The bandgap sizes of all con?gurations are also hydrogen dependent, and wider than that of pristine 2D?GaAs with both PBE and HSE functionals. Even though DFT?vdW interactions increase the adsorption energies and reduce the equilibrium distances of H?GaAs systems, it presents, qualitatively, the same physical results on the stability and electronic properties of our studied systems with PBE functional. According to our results, two?dimensional buckled gallium arsenide is a good candidate to be synthesized by hydrogen surface passivation as its group III?V partners two-dimensional buckled gallium nitride and boron nitride. The hydrogenation of 2D-GaAs tunes the bandgap of pristine 2D-GaAs, which makes it a potential candidate for optoelectronic applications in the blue and violet ranges of the visible electromagnetic spectrum.
关键词： two-dimensional gallium arsenide.,hydrogen,bandgap tuning,Density Functional Theory
更新于2025-09-12 10:27:22
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Enhanced Moisture Stability by Butyldimethylsulfonium Cation in Perovskite Solar Cells
摘要： Many organic cations in halide perovskites have been studied for their application in perovskite solar cells (PSCs). Most organic cations in PSCs are based on the protic nitrogen cores, which are susceptible to deprotonation. Here, a new candidate of fully alkylated sulfonium cation (butyldimethylsulfonium; BDMS) is designed and successfully assembled into PSCs with the aim of increasing humidity stability. The BDMS-based perovskites retain the structural and optical features of pristine perovskite, which results in the comparable photovoltaic performance. However, the fully alkylated aprotic nature of BDMS shows a much more pronounced effect on the increase in humidity stability, which emphasizes a generic electronic difference between protic ammonium and aprotic sulfonium cation. The current results would pave a new way to explore cations for the development of promising PSCs.
关键词： perovskites solar cells,humidity stability,density functional theory (DFT),butylammonium iodide,butyldimethylsulfonium iodide
更新于2025-09-12 10:27:22
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The Effect of Chiral Ligand Concentration and Binding Mode on Chiroptical Activity of CdSe/CdS Quantum Dots
摘要： Chiroptically active fluorescent semiconductor nanocrystals, quantum dots (QDs), are of high interest from a theoretical and technological point of view as they are promising candidates for a range of potential applications. Optical activity can be induced in QDs by capping them with chiral molecules, resulting in circular dichroism (CD) signals in the range of the QD UV-Vis absorption. However, the effects of the chiral ligand concentration and binding modes on the chiroptical properties of QDs are still poorly understood. In the present study, we report the strong influence of the concentration of a chiral aminoacid (cysteine) on its binding modes upon the CdSe/CdS QD’s surface, resulting in varying QD chiroptical activity and corresponding CD signals. Importantly, we demonstrate that the increase of cysteine concentration is accompanied by the growth of the QD CD intensity, reaching a certain critical point after which it starts to decrease. The intensity of the CD signal varies by almost an order of magnitude across this range. NMR and FTIR data, supported by DFT calculations, reveal a change in the binding mode of cysteine molecules from tridentate to bidentate when going from low to high concentrations, which results in a change in the CD intensity. Hence, we conclude that the chiroptical properties of QDs are dependent on the concentration and binding modes of the capping chiral ligands. These findings are very important for understanding chiroptical phenomena at the nanoscale and for the design of advanced optically active nanomaterials.
关键词： cysteine,chiroptical activity,density functional theory,quantum dots,chirality,ligand concentration,binding mode
更新于2025-09-12 10:27:22
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Tuning the optoelectronic properties of oligothiophenes for solar cell applications by varying the number of cyano and fluoro substituents for solar cell applications: A theoretical study
摘要： Chemical modifications through substitution are observed to be effective in controlling the optoelectronic properties of various polymers for different applications. In this study, density functional theory–based calculations are employed to investigate the optoelectronic properties of several oligothiophenes based on poly(3-hexylthiophene-2,5-diyl) by varying the number of fluoro and cyano substituents attached. The resulting structures of the polymer derivatives are affected by the electrostatic interactions between the cyano or fluoro groups and the adjacent thiophene unit. Of the two, cyano substitution results in much lower frontier orbital energies for the same number of substituents. It was observed that a decrease in the highest occupied molecule orbital and lowest unoccupied molecular orbital energies correlates very strongly with the number of cyano and fluoro substituents. The effect of the cyano and fluoro groups on the frontier orbitals is also demonstrated and observed to correlate strongly with a lowering of the highest occupied molecule orbital and lowest unoccupied molecular orbital energies as the number of substituents is varied. The predicted solar cell characteristics reveal that most cyano and fluoro derivatives will have improved characteristics compared to unsubstituted poly(3-hexylthiophene-2,5-diyl). This theoretical study shows that by varying the number of electron-withdrawing substituents, the optoelectronic properties may be tuned for solar cell applications.
关键词： density functional theory,optoelectronic properties,organic solar cells,conjugated polymers,computational chemistry
更新于2025-09-12 10:27:22
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First-principles DFT insights into the structural, elastic, and optoelectronic properties of <i>α</i> and <i>β</i> -ZnP <sub/>2</sub> : implications for photovoltaic applications
摘要： Binary II–V semiconductors are highly optically active materials, possess high intrinsic mechanical and chemical durability, and have electronic properties ideal for optoelectronic applications. Among them, zinc diphosphide (ZnP2) is a promising earth-abundant absorber material for solar energy conversion. We have investigated the structural, mechanical, and optoelectronic properties of both the tetragonal (α) and monoclinic (β) phases of ZnP2 using standard, Hubbard-corrected and screened hybrid density functional theory methods. Through the analysis of bond character, band gap nature, and absorption spectra, we show that there exist two polymorphs of the β phase (denoted as β1 and β2) with distinct differences in the photovoltaic potential. While β1 exhibits the characteristics of metallic compounds, β2 is a semiconductor with predicted thin-film photovoltaic absorbing efficiency of almost 10%. The α phase is anticipated to be an indirect gap material with a calculated efficiency limited to only 1%. We have also analysed and gained insights into the electron localization function, projected density of states and projected crystal orbital Hamilton populations for the analogue bonds between the α and β-ZnP2. In light of these calculations, a number of previous discrepancies have been solved and a solid ground for future employment of zinc diphosphides in photovoltaics has been established.
关键词： photovoltaics,density functional theory,semiconductors,electronic structure
更新于2025-09-12 10:27:22