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Effect of the alkyl chain length on the optoelectronic properties of organic dyes: theoretical approach
摘要： In recent years, investigating organic compounds for Dye Sensitized Solar Cells (DSSCs) applications has received particular attention for its interesting optoelectronics properties. In this article, we have conducted a theoretical study on a series of D–π–A molecules, which have carbazole as a donor (D) and cyanoacrylic acid as acceptor (A) linked by a conjugated bridge. Theoretical calculations were conducted using Density Functional Theory (DFT) and Time-Dependent-DFT to evaluate the substitution effect of linear chains and to elucidate the effects of alkyl chain length (R: H, CH3 to C6H13). We have studied the geometrical structures, the electronic and optical properties, the conduction band shift, as well as the charge transfer parameters: IP, EA, PEE, HEP, λ, LHE, Voc, ΔGinject and ΔGreg of the studied dyes. According to the results obtained, the substitution of hydrogen H (Dye 1) by the methyl group CH3 (Dye 2) has, on the one hand, a significant effect on the values of the energies HOMO and LUMO, and on the other hand, the absorption peak is redshifted and the contribution of the electronic transition (H → L) has been improved (664.17 nm and 70%, respectively). However, the substitution of CH3 (Dye 2) by the other alkyl groups CnH2n+1 (n = 2 to 6) (Dye 3 to Dye 7) has low effects. The best results are obtained by substitution with methyl CH3, and the increase in chain length, which will require additional computing time, has a low effect on the properties of the dyes studied.
关键词： DFT,Optoelectronic properties,Alkyl chain length,Dyes
更新于2025-09-23 15:21:01
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DFT and TD-DFT studies of new pentacene-based organic molecules as a donor material for bulk-heterojunction solar cells
摘要： The performance of organic cells based on bulk heterojunctions (BHJs) has improved recently, but further improvements are necessary. In this work, we have carried out a thorough examination using density functional theory (DFT) and time-dependent (TD)-DFT to investigate the structural and optoelectronic properties of pentacene-based organic molecules (PbOMs) as potential donor material for organic photovoltaic BHJ devices. Our results show that oxadiazole prefers to attach via its nitrogen atoms to the carbon atoms of the pentacene monomer with an adsorption energy about ? 32.86 kcal/mol, which means that oxadiazole is efficiently adsorbed on the edge of the pentacene. The HOMO energy level of the PbOM with the lowest bandgap is ? 4.00 eV wide, i.e., about 0.86 eV lower and more positive than pentacene, thus providing an ideal open-circuit voltage for photovoltaic devices. The bandgap of the PbOM compounds are about 1.61 and 1.80 eV affording an efficient charge transfer from donor to acceptor. Furthermore, the donor PbOMs are also more stable than the pentacene. We have examined, additionally, the reactivity and absorption properties of individual molecules and PbOM systems. Our results suggest that the PbOM, as a donor material, may significantly improve the efficiency of BHJ solar cells.
关键词： TD-DFT,Pentacene,Bulk-heterojunction,Donor material
更新于2025-09-23 15:21:01
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Computational design of new organic (Da????a??A) dyes based on benzothiadiazole for photovoltaic applications, especially dye-sensitized solar cells
摘要： A theoretical study on four organic dyes based on bis(4-hexyloxy)triphenylamine as donor and electron acceptor cyanoacrylic acid with a donor–π–acceptor structure (D–π–(D–A–)–A) using DFT/DFT (TD-DFT)/6-31G(d,p) having a difference of π spacer was designed. The theoretical study of the structural, electronic and optical properties of these dyes (D1, D4) suggests that these materials would be excellent sensitizers as a candidate for the production of dye solar cells, due to the efficient photoinduced electron transfer and strong absorption as well as the electronic properties (HOMO, LUMO, Egap) low band gap, The improved light-harvesting efficiency and free energy change of electron injection (ΔGinject), of new designed sensitizers revealed that these materials would be excellent sensitizers. This theoretical designing paves the way for experimentalists to synthesize more efficient sensitizers for solar cells.
关键词： DFT,Dye-sensitized solar cells,Organic dyes,Photovoltaic organic
更新于2025-09-23 15:21:01
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Designing indenothiophene-based acceptor materials with efficient photovoltaic parameters for fullerene-free organic solar cells
摘要： Non-fullerene small molecular acceptors (NFSMAs) exhibit promising photovoltaic performance which promoted the rapid progress of organic solar cells (OSCs). In this study, an attempt is done to explore indenothiophene-based high-performance small molecular electron acceptors for organic solar cells. We have designed five acceptor molecules (M1–M5) with strong donor moiety indenothiophene linked to five different end-capped group acceptor moieties: diflouro-2-methylene-3-oxo-2,3-dihydroindene-1-ylidene)malononitrile (A1), 1-(dicyanomethylene)-2-methylene-3-oxo-2,3-dihydro-1H-indene-5,6-dicarbonitrile (A2), methyl-6-cyano-3-(dicyanomethylene)-2-methylene-1-oxo-2,3-dihydro-1H-indene-5-carboylate (A3), 2-(6-cyano-5-fluoro-2-methylene-3-oxo-2,3 dihydro-1H-indene-1-ylidene)malononitrile (A4), and (Z)-methyl 3-(benzo [c][1,2,5]thiadiazol-4-yl)-2-cyanoacrylate (A5) respectively. The structure–property relationship was studied and effects of structural modification on the optoelectronic properties of these acceptors (M1–M5) were determined systematically by comparing it with reference molecule R, which is recently reported as excellent non-fullerene-based small acceptor molecule. Among all designed molecules, M5 is proven as a suitable candidate for organic solar cell applications due to better photovoltaic properties including narrow HOMO-LUMO energy gap (2.11 eV), smallest electron mobility (λe = 0.0038 eV), highest λmax values (702.82 nm in gas) and (663.09 nm in chloroform solvent) and highest open-circuit voltage (Voc = 1.49 V) with respect to HOMOPTB7-Th–LUMOacceptor. Our results indicate that introducing more end-capped electron-accepting units is a simple and effective alternative strategy for the design of promising NFSMAs. This theoretical framework also proves that the conceptualized NFSMAs are superior and thus are recommended for the future construction of high-performance organic solar cell devices.
关键词： Photovoltaic properties,Indenothiophene,Density functional theory (DFT),Non-fullerene acceptor materials,Organic solar cells (OSCs)
更新于2025-09-23 15:21:01
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Investigation of the structural and electronic properties of InP1-xSbx alloy for mid-infrared optoelectronic applications: A TB-mBJ DFT study
摘要： The structural and electronic properties of InP1(cid:1)xSbx supercell structure at different percent of Sb incorporation have been studied under the Density Functional Theory formalism employing WIEN2K package. From the total energy calculations, the supercell lattice structures have been optimized. The structural properties have been calculated from the equation of state which suggests the supercell structures to be signi?cantly stable with a higher degree of compressive ?exibility (speci?cally, at lower percent of Sb incorporation). The contribution of the partial and total DOS (Density of States) of constituent elements to total DOS of the supercell structure has been investigated. The relativistic effects have been assimilated into the band structure calculation, along various high symmetry k directions for each supercell structure. The values obtained for band gap (both, direct and indirect), spin-orbit splitting energy and bowing coef?cient have been observed to vary signi?cantly as a function of Sb mole fraction. Moreover, a relationship has been established between band gap (both, direct and indirect) values and spin-orbit splitting energy with Sb mole fraction. The in?uence of SOC (spin-orbit coupling) effect on the parameters concerning electronic properties has also been analyzed. The effective mass values for conduction and valence sub-bands (heavy hole, light hole and spin orbit split-off hole) near the Brillouin zone has been calculated at different percent of Sb incorporation in InP1(cid:1)xSbx supercell structure. The interpretation of these results obtained suggests InP1(cid:1)xSbx material to be competent for mid-infrared optoelectronic applications.
关键词： III-V semiconductor,Electronic band structure,DOS,DFT calculation,Effective mass calculation,Structural and electronic property
更新于2025-09-23 15:21:01
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Chromophores in cellulosics, XVIII. Degradation of the cellulosic key chromophore 5,8-dihydroxy-[1,4]-naphthoquinone under conditions of chlorine dioxide pulp bleaching: a combined experimental and theoretical study
摘要： DHNQ is one of the key chromophores occurring in all types of aged cellulosics. This study investigates the degradation of DHNQ by chlorine dioxide at moderately acidic (pH 3) conditions, corresponding to the conditions of industrial bleaching ("D stage"). The degradation involves three major pathways. As initial reaction, a hydrogen transfer from DHNQ to chlorine dioxide via a PCET mechanism occurs to form a radical DHNQ(cid:2) and chlorous acid. DHNQ(cid:2) is then attacked by water to give a pentahydroxynaphthalene radical PHN(cid:2) that is stabilized by strong delocalization of the non-paired electron into its aromatic ring. PHN(cid:2) immediately disproportionates to give the observable intermediate 1,2,4,5,8-pentahydroxynapththalene (I), which was comprehensively con?rmed by NMR and MS (path A). In the presence of excess ClO2, I is immediately further oxidized into acetic acid, glycolic acid, oxalic acid and CO2 as the ?nal, stable, and non-colored products (path C). In the absence of excess ClO2, elimination of water from I regenerates DHNQ (path B), so that at roughly equimolar DHNQ/ClO2 ratios ClO2 is fully consumed while a major part of DHNQ is recovered. To avoid such DHNQ "recycling" under ClO2 consumption—and to completely degrade DHNQ to colorless degradation products instead—ClO2 must be applied in at least ?vefold molar excess relative to DHNQ.
关键词： Density functional theory (DFT),Ab initio calculations,Yellowing,Cellulose,Brightness,Chromophores,5,8-dihydroxy-[1,4]-naphthoquinone,Chlorine dioxide,Brightness reversion,Pulp bleaching
更新于2025-09-23 15:21:01
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Ti, Zn co-doped hematite photoanode for solar driven photoelectrochemical water oxidation
摘要： Although there have been many reports of metal doping to ameliorate the drawbacks of hematite as the photoanode for water oxidation, most of them focused on monometallic doping, and only a few of them payed attention to bimetallic doping. What is worse, the synergetic mechanism between two metal dopants was not su?ciently studied, especially the density functional theory (DFT) calculation. In this work, the n-type hematite was synthesized by introducing Ti dopant into hematite through the hydrothermal method, and dipping-sintering treatment was employed to further introduce homogeneously dispersed Zn dopant into that, forming the Ti, Zn co-doped hematite. Under the optimal condition, Ti-doped hematite photoanode reached approximately 2-times enhancement of the photocurrent density compared with the pristine one at 1.23 V vs. RHE, while Ti, Zn co-doped hematite anode obtained another 25% elevation. UV –Vis spectroscopy, Mott –Schottky plots, EIS analysis, photo-oxidation of hole scavenger (H 2 O 2 ), and DFT calculation were employed to understand the role of Ti, Zn dopant. Based on the obtained results, the synergetic mechanism of two dopants was discussed, i.e., the improvement of PEC performance of Ti, Zn co-doped hematite photoanode was possibly attributed to greater carrier density and improved charge separation e?ciency at the surface of hematite. This work provides new strategy and understanding of the improvement of PEC performance of hematite by doping engineering.
关键词： Photoelectrochemical water oxidation,Zn co-doping,Ti,DFT calculation,Hematite
更新于2025-09-23 15:21:01
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Theoretical studies on D-A-??-A and D-(A-??-A)2 dyes with thiophene-based acceptor for high performance p-type dye-sensitized solar cells
摘要： Eight p-type dyes with D-A-π-A or D-(A-π-A)2 structures were designed to investigate the effect of thiophene derivatives acting as acceptors on the properties of the sensitizers. Structure optimizations were performed by the density functional theory (DFT) method, and the electronic and absorption characters were obtained with the time-dependent DFT (TD-DFT). The results show that all the eight dyes have an excellent light harvesting efficiency (LHE) performance (0.99–1.00). And the driving forces of hole injection (ΔGinj) and dye regeneration (ΔGreg) of all dyes are more negative than (cid:0) 0.2 eV, resulting in an efficient hole injection and dye regeneration. Furthermore, the dyes with 2,3-dimethylpyrazine thiophene moiety (DMPZT-1) have the narrowest energy gaps. Importantly, the dyes with DMPZT-1 moiety display red shifts of the UV–vis absorption and enhanced absorptions of visible light (400–800 nm) in comparison to their prototype. In addition, the charge recombination (ΔGCR) performance of A1 and B1 is improved by DMPZT-1. Compared with the D-A-π-A dyes, the additional -A-π-A chain in D-(A-π-A)2 could decrease energy gap further and improve the visible light adsorption, LHE, and driving forces for hole injection and charge regeneration (ΔGinj and ΔGreg). Replacing thiophene with DMPZT-1 acceptor is an effective way to improve the performance of the dyes.
关键词： DFT,p-type organic sensitizers,DSSCs,D-A-π-A,Thiophene derivatives
更新于2025-09-23 15:21:01
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Synthesis, DFT studies, fabrication, and optical characterization of the [ZnCMC] <sup>TF</sup> polymer (organic/inorganic) as an optoelectronic device
摘要： A novel carboxymethyl cellulose zinc thin film [ZnCMC]TF was fabricated using the sol–gel technique. Different characterization techniques such as Fourier-transform infrared spectroscopy (FTIR), Raman spectroscopy, ultraviolet–visible spectroscopy (UV-Vis), X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDX), and the optical properties were used to study the properties of [ZnCMC]TF. The molecular structure, FTIR, and optical properties were optimized. The Raman spectrum of the [ZnCMC]TF complex shows several bands in the range of 72–556 cm?1 due to (nZn–O) stretching and (Zn–O) bending, which is an obvious distinction between the FTIR and Raman spectra of [ZnCMC]TF. The optimization was performed using density functional theory (DFT) by DMol3 and Cambridge Serial Total Energy Package (CASTEP) program. The chemical structure was confirmed by spectroscopic and structural properties for both CMC and [ZnCMC]TF; the XRD results showed the same crystal structure (Monoclinic 2). [ZnCMC]TF has a larger grain size than CMC and has a similar behavior in the optical gap energy. The optical constants increased with increasing photon energy, refractive index n, absorption index k, and optical conductivity. The SEM images provide very good evidence in favor of the reaction of zinc transition metal with CMC for the formation of the [ZnCMC]TF complex. The resulting [CMC] spherical thin film and the [ZnCMC]TF polymeric nanorods were examined by different techniques including TEM and EDX. The optical properties obtained from the simulated FTIR, XRD, and CASTEP are in good agreement with those obtained from the experimental studies on CMC and ZnCMC. Based on the optical findings, [ZnCMC]TF is a promising candidate in applications such as solar cells and optoelectronic devices.
关键词： TEM,DMol3,zinc thin film,carboxymethyl cellulose,UV-Vis,DFT,optoelectronic devices,XRD,EDX,CASTEP,sol–gel technique,SEM,FTIR,optical properties,Raman spectroscopy
更新于2025-09-23 15:21:01
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Theoretical study of new conjugated compounds with a low bandgap for bulk heterojunction solar cells: DFT and TD-DFT study
摘要： Bulk heterojunction solar cells have attracted scientific and economic interest in recent years, and have just been one of the future photovoltaic technologies to produce energy at low cost. To study the electronic and geometric properties of a novel conjugated polymer called r-PTTDPP50, which is formed from a derivative of diketopyrrolopyrrole (DPP), thiophene conjugated side chain and 2, 5-bis (trimethylstannyl) thiophene, functional density theory (DFT) has been used with several methods such as B3LYP, PBEPBE, B3PW91 and mPW1PW91 and the basis set 6-31G (d, p),to obtain the most appropriate method. The absorption properties have been obtained by the CAM-B3LYP method. Then, the functional tests giving the closest result to the experimental ones will be used to propose other structure candidates for applications in the domain of organic electronics. This research has been used to conduct next syntheses to compounds more helpful as active materials in optoelectronic.
关键词： Bulk heterojunction,DFT,solar cells,diketopyrrolopyrrole (DPP),thiophene
更新于2025-09-23 15:21:01