Anthracene-bridged sensitizers for environmentally compatible dye-sensitized solar cells: In silico modelling and prediction.

Advancement in solar cells has gained the attention of researchers due to increasing demand and renewable energy sources. Modeling of electron absorbers and donors has been performed extensively for the development of efficient solar cells. In this regard, efforts are being made for designing effective units for the active layer of solar cells. In this study, CXC22 was utilized as a reference in which acetylenic anthracene acted as a π bridge and infrastructure was D-π-A. We theoretically designed four novel dye-sensitized solar cells JU1-JU4 by utilizing reference molecules to improve the photovoltaic and optoelectronic properties. All designed molecules differ from R by donor moiety modifications. Different approaches were done to R and all molecules to explore different analyses like binding energies, excitation energies, dipole moment, TDM (transition density matrix), PDOS (partial density of states), absorption maxima, and charge transfer analysis. For the evaluation of results, we used the DFT technique and the findings demonstrated that the JU3 molecule showed a better redshift absorption value (761 nm) as compared to all other molecules due to the presence of anthracene in the donor moiety which lengthens the conjugation. JU3 was proven to be the best candidate among all due to improved excitation energy (1.69), low energy band gap (1.93), higher λmax value, and improved electron and hole energy values leading toward higher power conversion efficiency. All the other theoretically formed molecules exhibited comparable outcomes as compared to a reference. As a result, this work revealed the potential of organic dyes with anthracene bridges for indoor optoelectronic applications. These unique systems are effective contributors to the development of high-performance solar cells. Thus, we provided efficient systems to the experimentalists for the future development of solar cells.

High electron mobility due to extra π-conjugation in the end-capped units of non-fullerene acceptor molecules: a DFT/TD-DFT-based prediction.

A combination of high open-circuit voltage (Voc) and short-circuit current density (Jsc) typically creates effective organic solar cells (OSCs). To enhance the open-circuit voltage, we have designed three new fullerene-free acceptor molecules with elongated π-conjugation in the end-capped units. Y-series-based newly designed molecules (CPSS-4F, CPSS-4Cl, CPSS-4CN) exhibited a narrow energy bandgap with high electron mobility. Red shift in the absorption spectrum with high intensities is also noted for designed molecules. Low binding and excitation energies of designed molecules favor easy excitation of exciton in the excited state. Further, CPSS-4F, CPSS-4Cl, and CPSS-4CN exhibited better open-circuit voltage with favorable molecular orbitals contributions. Transition density analysis (TDM) was also performed to locate the total transitions in the designed molecules. Outcomes of all analyses suggested that designed molecules are effective contributors to the active layer of organic solar cells.

Efficient designing of half-moon-shaped chalcogen heterocycles as non-fullerene acceptors for organic solar cells.

One key strategy to further improve the power conversion efficiency (PCE) of organic solar cells (OSCs) is to incorporate various complementary functional groups in a molecule. Such strategies proved attractive for tuning the photovoltaic performances of the materials and can show a much higher absorption phenomenon with narrower band gaps. Despite the outstanding benefits, materials selection and their efficient modeling is also an extremely challenging job for the development of OSCs materials. In this manuscript, we proficiently developed an efficient series of small molecule-based non-fullerene acceptors (SM-NFAs) SN1-SN9 for OSCs and characterized by density functional theory (DFT) and time-dependent DFT (TD-DFT). The characteristics required to estimate electron and hole mobility, and open-circuit voltage (Voc) were investigated by optimizing the geometrical parameters, absorption spectra, exciton binding energy, frontier molecular orbitals (FMOs), electronic structures, and charge transfer rates. The outcomes of these materials showed that all newly constructed small-molecule-based non-fullerene acceptors exhibit broader and better absorption efficiency (λmax = 761 to 778 nm) and exciton dissociation, while much lower LUMO energy levels which may help to enhance the reorganizational energies. Further, a narrow bandgap also offers better photovoltaic properties. Hence, the designed molecules exhibited narrow bandgap values (Eg = 2.82 to 2.98 eV) which are lower than that of the reference molecule (3.05 eV). High Voc and photocurrent density values with lower excitation and binding energies eventually increase the PCEs of the OSC devices. The obtained results have shown that designed molecules could be effective aspirants for high-performance OSCs.

Quinoxaline based unfused non-fullerene acceptor molecules with PTB7-Th donor polymer for high performance organic solar cell applications.

Unfused non-fullerene acceptors possess advantages such as simplicity of synthesis, low toxicity, high yield with less manufacturing cost. In the present era, the rapid emergence of new unfused acceptors with high yields and stability is an urgent need. This report has developed four new fullerene-free quinoxaline-based unfused acceptor molecules (QX1 to QX4) for high-performance organic solar cell applications. All designed molecules have a long conjugating backbone which facilitates easy charge transportation between donor and acceptor ends. Different physiochemical, optoelectrical, and photovoltaic properties of designed molecules have been explored through density functional theory (DFT), and time-density functional theory (TD-DFT). A significant reduction in energy bandgap with red-shifting in absorption spectrum was noted for QX1 to QX4. Further, QX1 to QX4 exhibited good values of open-circuit voltage with low excitation and binding energies. Transition density matrix (TDM) analysis was also performed to explore the charge transfer behavior in the designed molecule. In addition, QX1 to QX4 expressed high mobility of electrons and holes with high molecular orbitals contributions. Outcomes of different geometric parameters suggested that QX1 to QX4 are excellent acceptor molecules (when blended with PTB7-Th polymer) for the active layer of organic solar cells.

Quantum chemical designing of novel fullerene-free acceptor molecules for organic solar cell applications.

Organic solar cells (OSCs) with bulk heterojunction (BHJ) structures consisting of electron-donor and electron-acceptor materials have achieved impressive progress over the past decade, demonstrating their great potential in practical applications. In this study, we have designed five fullerene-free acceptor-based molecules containing indaceno-dithiophene as a central core moiety. We studied the optoelectronic features of these newly architecture molecules by using DFT and TD-DFT approaches. For the investigation of the optoelectronic characteristics of the reference and newly designed molecules, we performed different parameters including FMO's, absorption maxima, excitation energy, transition density matrix (TDM) along with binding energy, dipole moment, the partial density of states, charge mobility, and charge transfer analysis. Among all engineered molecules, SK1 has proven to be the most efficient solar cell due to its promising optoelectronic and photovoltaic properties. SK1 reveals smaller band-gap (Egap = 1.959 eV) and lesser λh (0.0070 eV) and λe (0.0051 eV). SK1 illustrated comparable binding energy value (0.33 eV) and lowest excitation energy (1.62 eV) which will lead to improved power conversion efficiency values. The SK1 molecule demonstrated the highest λmax value (764 nm) in the solvent phase which could lead to redshift absorption for achieving the high efficiency of OSCs. This molecular modeling approves that the best working efficiency of organic solar devices can be achieved by terminal group modifications due to their promising photovoltaic and optoelectronic properties. It is evident from the current analysis that all the theoretically fabricated molecules (SK1-SK5) are fabulous and highly suggested to experimental workers for their synthesis and advancement of these highly competent solar devices in the future.

Role of acceptor guests in tuning optoelectronic properties of benzothiadiazole core based non-fullerene acceptors for high-performance bulk-heterojunction organic solar cells.

Recently, end-capped acceptors tailoring approach has attracted many researchers because of unceasing higher power conversion efficiencies (PCEs) of resulted compounds. By keeping in view, the crucial role of NFAs in bulk-heterojunction OSCs, herein, we molecularly engineered five new non-fullerene acceptor materials (Y6A1-Y6A5) by modifying a recently synthesized Y6 molecule (R), having 18% power conversion efficiency when combined with D18 donor polymer. The structural-elemental connection, physical-chemical, optoelectronic, and photovoltaic characteristics of novel deigned and reference material (R) are studied with advanced quantum-chemical modulations. Density functional theory and time dependent-density functional theory has been employed through various basis sets to investigate the designed molecules theoretically. Interestingly, all of the newly modeled materials displayed lower excitation energies with lower HOMO-LUMO energy-gaps in-contrast with R molecule. Moreover, a red-shifted absorption and lower reorganizational energies of electron and hole are also a novel feature of these designed materials. The lower binding energy values of modeled materials offers better charge separation and high photo-current density (Jsc) as compared to R. Transition density analysis, open circuit voltage, and molecular electrostatic potential analysis suggested that end-capped acceptors alteration of R molecule is an efficient approach for tuning the optoelectronic properties of non-fullerene-based acceptor molecules (Y6A1-Y6A5). In last, composite study of donor: acceptor (D18:Y6A2) complex has also been carried-out to realize the charge transfer process at the donor-acceptor interface. After all investigations, we hope that our theoretical modeled materials are superior than Y6 molecule, therefore, we endorse these materials for the synthesis to prepare highly-efficient BHJ-OSCs devices.

First theoretical framework of Z-shaped acceptor materials with fused-chrysene core for high performance organic solar cells.

Chrysene core containing fused ring acceptor materials have remarkable efficiency for high performance organic solar cells. Therefore, present study has been carried out with the aim to design chrysene based novel Z-shaped electron acceptor molecules (Z1-Z6) from famous Z-shaped photovoltaic material FCIC (R) for organic photovoltaic applications. End-capped engineering at two electron-accepting end groups 1,1-dicyanomethylene-3-indanone of FCIC is made with highly efficient end-capped acceptor moieties and impact of end-capped modifications on structure-property relationship, photovoltaic and electronic properties of newly designed molecules (Z1-Z6) has been studied in detail through DFT and TDDFT calculations. The efficiencies of the designed molecules are evaluated through energy gaps, exciton binding energy along with transition density matrix (TDM) analysis, reorganizational energy of electron and hole, absorption maxima and open circuit voltage of investigated molecules. The designed molecules exhibit red-shift and intense absorption in near-infrared region (683-749 nm) of UV-Vis-NIR absorption spectrum with narrowing of HOMO-LUMO energy gap from 2.31 eV in R to 1.95 in eV in Z5. Moreover, reduction in reorganization energy of electron from 0.0071 (R) to 0.0049 (Z5), and enhancement in open circuit voltage from 1.08 V in R to 1.20 V in Z5 are also observed. Twisted Z-shape of designed molecules prevents self-aggregation that facilitates miscibility of donor and acceptor. Low values of binding energy, excitation energy, and reorganizational energy (electron and hole) suggest that novel designed molecules offer high charge mobilities as compared to FCIC. Our findings indicate that these novel designed molecules can display better photovoltaic parameters and are suitable candidates if used in organic solar cells.

Designing of benzodithiophene core-based small molecular acceptors for efficient non-fullerene organic solar cells.

Nowadays, organic solar cells (OSCs) with non-fullerene electron acceptors provide the highest efficiencies among all studied OSCs. To further improve the efficiencies of fullerene-free organic solar cells, end-capped acceptor modification is made with strong electron withdrawing groups. In this report, we have theoretically designed five new novel Benzodithiophene core-based acceptor molecules (H1-H5) with the aim to study the possible enhancement in photophysical, optoelectronic, and photovoltaic properties of newly designed molecules. The end-capped acceptor modification of famous and recently synthesized FBDIC molecule has been made with strong electron withdrawing groups. Density functional theory and time-dependent-density functional theory are extensively used to study the structural-property relationship, optical properties and various geometrical parameters like frontier molecular orbitals alignment, excitation and binding energy, transition density matrix along with open circuit voltage, density of states and dipole moment. Commonly, low reorganization energies (hole and electron) afford high charge mobility and our all designed systems are enriched in aspect (λe = 0.0044-0.0104 eV and λh = 0.0060-0.0090 eV). Moreover, H1-H5 molecules demonstrate red-shifting in absorption spectrum (λmax = 741-812 nm) as compare to R (λmax = 728 nm). Low excitation and binding energies with low HOMO (highest occupied molecular orbital)-LUMO (lowest unoccupied molecular orbital) energy gap of H1-H5 suggested that designed molecules are better and suitable candidates for high performance organic solar cell. Results of all analysis indicate that this theoretical framework demonstrates that end-capped acceptors modification is a simple and effective alternative strategy to achieve the desirable optoelectronic properties. Therefore, H1-H5 are recommended to experimentalist for out-looking future developments of highly efficient solar cells.

Efficient tuning of zinc phthalocyanine-based dyes for dye-sensitized solar cells: a detailed DFT study.

The growing energy demand speed up the designing of competent photovoltaic materials. Herein, five zinc phthalocyanine-based donor materials T1-T5 are designed by substituting various groups (isopropoxy, cyano, fluoro, methoxycarbonyl, and dicyanomethyl) around zinc phthalocyanine. B3LYP/6-31G (d,p) level density functional theory (DFT) was used to investigate the optoelectronic properties of five zinc phthalocyanine-based dyes T1-T5 for dye-sensitized solar cells. The designed molecule T1 shows maximum absorption wavelength (λ max) in the absorption spectrum at 708.89 and 751.88 nm both in gaseous state and in THF (tetrahydrofuran) solvent. The E g value of T1 (1.86 eV) is less than reference R, indicating a greater charge transfer rate for T1 among the molecules. The values of open-circuit voltages achieved with acceptor polymer PC71BM are higher than R except for T1 and are 0.69 V, 1.95 V, 1.20 V, 1.44 V, and 1.84 V for T1, T2, T3, T4, and T5, respectively. The lower the reorganization energy, the higher the charge transfer for T1 due to its lower hole mobility (0.06297 eV) than R. Thus, the designed T1-T5 molecules are expected to exhibit superior performance in dye-sensitized solar cells.

Designing Novel Zn-Decorated Inorganic B12P12 Nanoclusters with Promising Electronic Properties: A Step Forward toward Efficient CO2 Sensing Materials.

Gas sensing materials have been widely explored recently owing to their versatile environmental and agriculture monitoring applications. The present study advocates the electronic response of Zn-decorated inorganic B12P12 nanoclusters to CO2 gas. Herein, a series of systems CO2-Zn-B12P12 (E1-E4) are designed by adsorption of CO2 on Zn-decorated B12P12 nanoclusters, and their electronic properties are explored by density functional theory. Initially, placement of Zn on B12P12 delivers four geometries named as D1-D4, with adsorption energy values of -57.12, -22.94, -21.03, and -14.07 kJ/mol, respectively, and CO2 adsorption on a pure B12P12 nanocage delivers one geometry with an adsorption energy of -4.88 kJ/mol. However, the interaction of CO2 with D1-D4 systems confers four geometries named as E1 (E ad = -75.12 kJ/mol), E2 (E ad = -25.89 kJ/mol), E3 (E ad = -42.43 kJ/mol), and E4 (E ad = -28.73 kJ/mol). Various electronic parameters such as dipole moment, molecular electrostatic potential analysis, frontier molecular orbital analysis, Q NBO, global descriptor of reactivity, and density of states are also estimated in order to understand the unique interaction mechanism. The results of these analyses suggested that Zn decoration on B12P12 significantly favors CO2 gas adsorption, and a maximum charge separation is also noted when CO2 is adsorbed on the Zn-B12P12 nanocages. Therefore, the Zn-decorated B12P12 nanocages are considered as potential candidates for application in CO2 sensors.

Designing indenothiophene-based acceptor materials with efficient photovoltaic parameters for fullerene-free organic solar cells.

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. Graphical abstract.

Adsorption of Phosgene Gas on Pristine and Copper-Decorated B12N12 Nanocages: A Comparative DFT Study.

Nanostructured gas sensors find diverse applications in environmental and agricultural monitoring. Herein, adsorption of phosgene (COCl2) on pure and copper-decorated B12N12 (Cu-BN) is analyzed through density functional theory (DFT) calculations. Adsorption of copper on B12N12 results in two optimized geometries, named Cu@b66 and Cu@b64, with adsorption energies of -193.81 and -198.45 kJ/mol, respectively. The adsorption/interaction energies of COCl2 on pure BN nanocages are -9.30, -6.90, and -3.70 kJ/mol in G1, G2, and G3 geometries, respectively, whereas the interaction energies of COCl2 on copper-decorated BN are -1.66 and -16.95 kJ/mol for B1 and B2, respectively. To examine the changes in the properties of pure and Cu-BN nanocages, geometric parameters, dipole moment, Q NBO, frontier molecular orbitals, and partial density of states (PDOS) are analyzed to comprehensively illustrate the interaction mechanism. The results of these parameters reveal that COCl2 binds more strongly onto copper-doped BN nanocages. Moreover, a higher charge separation is observed in COCl2-Cu-BN geometries as compared to copper-decorated BN geometries. Therefore, these nanocages may be considered as potential candidates for application in phosgene sensors.

Density functional theory study of palladium cluster adsorption on a graphene support.

The geometric, thermodynamic and electronic properties of Pd-graphene nanocomposites are comprehensively studied through quantum mechanical methods. Geometries of these clusters are optimized with the well-calibrated Minnesota functional M06-2X. The adsorption energies calculated at the M06-2X/LANL2DZ level show better agreement with those calculated from MP2/ANO-RCC-VDZP. Two different representative models for graphene, coronene and hexabenzocoronene, are used. The adsorption energies analysis reveals that the interaction energies increase with the size of the adsorbed cluster. However, for Pd n /hexabenzocoronene, the interaction energies show a sudden drop at Pd8/hexabenzocoronene. The difference in behavior between the interaction energies of Pd n /hexabenzocoronene and Pd n /coronene is attributed to the edge effect present in coronene. The electronic properties, including highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO), Fermi level, molecular electrostatic potential (MEP), dipole moment, vertical ionization potential (VIP), vertical electron affinity (VEA), chemical hardness (η), softness (S) and chemical potential (µ) are studied. The VIP and VEA reveal that Pd n /coronene clusters are stable in nature with the least reactivity. The HOMO-LUMO energy gaps are reduced with the increase in cluster size. The electronic properties show irregular trends, where the most favorable electronic properties are obtained for Pd7/coronene and Pd10/coronene.