Tuning of a A-A-D-A-A-Type Small Molecule with Benzodithiophene as a Central Core with Efficient Photovoltaic Properties for Organic Solar Cells

Photophysical properties of donor (D)-acceptor (A)-donor (D) diketopyrrolopyrrole (A) systems as donors for applications to organic electronic devices

Fourteen substituted diketopyrrolopyrrole (DPP) molecules in a donor (D)-acceptor (DPP)-donor (D) arrangement were designed. We employed density functional theory, time-dependent DFT, DFT-MRCI and the ab initio wave function second-order algebraic diagrammatic construction (ADC(2)) methods to investigate theoretically these systems. The examined aromatic substituents have one, two, or three hetero- and non-hetero rings. We comprehensively investigated their optical, electronic, and charge transport properties to evaluate potential applications in organic electronic devices. We found that the donor substituents based on one, two, or three aromatic rings bonded to the DPP core can improve the efficiency of an organic solar cell by fine-tuning the highest occupied molecular orbital/lowest unoccupied molecular orbital levels to match acceptors in typical bulk heterojunctions acceptors. Several properties of interest for organic photovoltaic devices were computed. We show that the investigated molecules are promising for applications as donor materials when combined with typical acceptors in bulk heterojunctions because they have appreciable energy conversion efficiencies resulting from their low ionization potentials and high electron affinities. This scenario allows a more effective charge separation and reduces the recombination rates. A comprehensive charge transfer analysis shows that D-A (DDP)-D systems have significant intramolecular charge transfer, further confirming their promise as candidates for donor materials in solar cells. The significant photophysical properties of DPP derivatives, including the high fluorescence emission, also allow these materials to be used in organic light-emitting diodes.

Unveiling peripheral symmetric acceptors coupling with tetrathienylbenzene core to promote electron transfer dynamics in organic photovoltaics

Non-fullerene organic compounds are promising materials for advanced photovoltaic devices. The photovoltaic and electronic properties of the derivatives (TTBR and TTB1-TTB6) were determined by employing density functional theory (DFT) and time-dependent density functional theory (TD-DFT) analyses using the M06/6-311G(d,p) functional. To enhance the effectiveness of fullerene-free organic photovoltaic cells, modifications were applied to end-capped acceptors by using strong electron-withdrawing moieties. The structural tailoring showed a significant electronic impact for HOMO and LUMO for all chromophores, resulting in decreased band gaps (3.184-2.540 eV). Interestingly, all the designed derivatives exhibited broader absorption spectra in the range of 486.365-605.895 nm in dichloromethane solvent. Among all derivatives, TTB5 was observed to be the promising candidate because of its lowest energy gap (2.54 eV) and binding energy (0.494 eV) values, along with the bathochromic shift (605.895 nm). These chromophores having an A-π-A framework might be considered promising materials for efficient organic cells.

Computational method on highly efficient D-π-A-π-D-based different molecular acceptors for organic solar cells applications and non-linear optical behaviour

Eight molecular structures (BT-A1 to BT-A8) with high-performance non-fullerene acceptor (NFA) were selected for organic solar cells (OSCs) and non-linear optical (NLO) applications. Their electronic, photovoltaic (PV) and optoelectronic properties were tuned by adding powerful electron-withdrawing groups to the acceptor (A) of the D-π-A-π-D structure. Using time-dependent density functional theory (TD-DFT) techniques, based on the laws of quantum chemical calculations, the absorption spectra, stability of the highest and lowest-energy molecular orbitals (HOMO/LUMOs), electron density, intramolecular charge transfer (ICT), transition density matrix (TDM), were examined. The binding energy (Eb) and density of states (DOS) were probed to realize the optoelectronic analysis of the structures BT-A1 to BT-A8. Noncovalent interactions (NCIs) based on a reduced density gradient (RDG) were used to describe the nature and strength of D-A interactions in the molecules BT-A1 to BT-A8. The new refined molecules BT-A1 to BT-A8 exhibited strong absorbance bands between 408-721 nm and high electron transfer contribution (ETC) ranges between 87-96 %, along with the smallest excitation energies (Ex) between 1.71-3.55 eV in the solvent dichloromethane. Dipolar moment strengths ranging from 0.38 to 4.72 Debye in both the excited and ground states have determined with good solubility properties of BT-A1 to BT-A8 in polar solvent. Highly effective charge mobilities and prevention of charge recombination have been demonstrated by the electron (0.18-0.41 eV) and hole RE values (0.13-0.89 eV) for the new compounds. Power conversion efficiencies (PCE) of BT-A1 to BT-A8 were nearly the same because of better outcomes compared to the molecules in the BT. Compared to poly[4.8-bis(5-(2-ethylhexyl)thiophen-2-yl)benzo[1,2-b: 4,5-b']dithiophene-2,6- diyl-alt-(4-2-ethylhexyl)-3-fluorothieno[3,4-b]thiophene-)-2-carboxylate-2-6-diyl)] (PTB7-Th), the open circuit voltages (Voc) of compounds BT-A1 to BT-A8 were ranged from 1.52 to 2.13 eV. The polarizability (α) and hyperpolarizability (β) of the molecules BT-A1 to BT-A8 were used to determine the non-linear optical (NLO) properties. The results showed that BT-A2, BT-A6 and BT-A7 have good NLO activity. This computational analysis demonstrates the superiority of the molecules with NFA. Hence the compounds are advised for the use in production of high-performance OSCs and NLO activity.

DFT-Computational Modeling and TiberCAD Frameworks for Photovoltaic Performance Investigation of Copper-Based 2D Hybrid Perovskite Solar Absorbers

In this work, we use a combination of dispersion-corrected density functional theory (DFT-D3) and the TiberCAD framework for the first time to investigate a newly designed and synthesized class of (C6H10N2)[CuCl4] 2D-type perovskite. The inter- and intra-atomic reorganization in the crystal packing and the type of interaction forming in the active area have been discussed via Hirshfeld surface (HS) analyses. A distinct charge transfer from CuCl4 to [C6H10N2] is identified by frontier molecular orbitals (FMOs) and density of states (DOS). This newly designed narrow-band gap small-molecule perovskite, with an energy gap (E g) of 2.11 eV, exhibits a higher fill factor (FF = 81.34%), leading to an open-circuit voltage (V oc) of 1.738 V and a power conversion efficiency (PCE) approaching ∼10.20%. The interaction between a donor (D) and an acceptor (A) results in a charge transfer complex (CT) through the formation of hydrogen bonds (Cl-H), as revealed by QTAIM analysis. These findings were further supported by 2D-LOL and 3D-ELF analyses by visualizing excess electrons surrounding the acceptor entity. Finally, we performed numerical simulations of solar cell structures using TiberCAD software.

Unveiling the influence of end-capped acceptors modification on photovoltaic properties of non-fullerene fused ring compounds: a DFT/TD-DFT study

Herein, unique A-D-A configuration-based molecules (NBD1-NBD7) were designed from the reference compound (NBR) by utilizing the end-capped acceptor modification approach. Various electron-withdrawing units -F, -Cl, -CN, -NO2, -CF3, -HSO3, and -COOCH3, were incorporated into terminals of reference compound to designed NBD1-NBD7, respectively. A theoretical investigation employing the density functional theory (DFT) and time-dependent DFT (TD-DFT) was performed at B3LYP/6-311G(d,p) level. To reveal diverse opto-electronic and photovoltaic properties, the frontier molecular orbitals (FMOs), absorption maxima (λ max), density of states (DOS), exciton binding energy (E b), open-circuit voltage (V oc) and transition density matrix (TDM) analyses were executed at the same functional. Moreover, the global reactivity parameters (GRPs) were calculated using the HOMO-LUMO energy gaps from the FMOs. Significant results were obtained for the designed molecules (NBD1-NBD7) as compared to NBR. They showed lesser energy band gaps (2.024-2.157 eV) as compared to the NBR reference (2.147 eV). The tailored molecules also demonstrated bathochromic shifts in the chloroform (671.087-717.164 nm) and gas phases (623.251-653.404 nm) as compared to NBR compound (674.189 and 626.178 nm, respectively). From the photovoltaic perspectives, they showed promising results (2.024-2.157 V). Furthermore, the existence of intramolecular charge transfer (ICT) in the designed compounds was depicted via their DOS and TDM graphical plots. Among all the investigated molecules, NBD4 was disclosed as the excellent candidate for solar cell applications owing to its favorable properties such as the least band gap (2.024 eV), red-shifted λ max in the chloroform (717.164 nm) and gas (653.404 nm) phases as well as the minimal E b (0.126 eV). This is due to the presence of highly electronegative -NO2 unit at the terminal of electron withdrawing acceptor moiety, which leads to increased conjugation and enhanced the intramolecular charge transfer (ICT) rate. The obtained insights suggested that the designed molecules could be considered as promising materials for potential applications in the realm of OSCs.

Rational Design of New Small Derivatives of 2,2'-Bithiophene as Hole Transport Material for Perovskite Solar Cells

Using Density Functional Theory (DFT) and Time Dependent DFT (TD-DFT) methods, this inquiry theoretically examines seven novel hole-transport materials (HTMs) namely DFBT1, DFBT2, DFBT3, DFBT4, DFBT5, DFBT6, and DFBT7 based on the 2,2'bithiophene core for future use as HTMs for perovskite solar cells (PSCs). The model molecule has been modified through substituting the end groups situated on the diphenylamine moieties with a tow acceptor bridged by thiophene, this modification was performed to test the impact of the π-bridge and acceptor on the electronic, photophysical, and photovoltaic properties of the newly created molecules. DFBT1 - DFBT7 displayed a lower band gap (1.49 eV to 2.69 eV) than the model molecule (3.63 eV). Additionally, the newly engineered molecules presented a greater λmax ranging from 393.07 nm to 541.02 nm in dimethylformamide solvent, as compared to the model molecule (380.61 nm). The PCEs of all newly designed molecules (22.42% to 29.21%) were high compared with the reference molecule (19.62%). Thus, this study showed that all seven newly small molecules were excellent candidates for a novel PSC.

Design a New D-π-A Formation Dyes as Dye-sensitized Solar Cells Applications/ a DFT and TD-DFT Study

Dye-sensitized solar cells (DSSCs) have garnered significant interest among researchers in the field of photovoltaics due to their promising performance, low cost and easy process of fabrication. In this study, we have designed new D-π-A systems as derivatives of the reference (Ref. A) D-A-D scaffold, incorporating different π-bridges to enhance and optimize their efficiency as sensitizing dyes for DSSCs applications. Density functional theory (DFT) and time-dependent DFT (TD-DFT) methods were employed to investigate the geometrical and electronic structures, chemical reactivity indices, optical properties, exciton binding energy, and electrochemical properties of these dyes. We also examined the preferred adsorption process of the two selected dyes on a (TiO2)15 cluster model. The results demonstrate that all the dyes exhibit improved open-circuit photovoltage, enhanced light-harvesting efficiencies, higher electron injection efficiency, and excellent photovoltaic efficiency. Moreover, there is evidence of electron injection occurring from each studied dye to the conduction band of TiO2, followed by efficient regeneration. The introduced bridges in the molecular systems play a crucial role in facilitating electron transfer from the donor to the acceptor region. Comparatively, the D-π-D systems exhibit superior performance in DSSCs compared to Ref. A, which can be attributed to their higher energy levels of the lowest unoccupied molecular orbital and larger oscillator strengths for the most excited states involving intramolecular electron transfer and the electron injection process occurring from each examined molecule to the conduction band of TiO2, followed by subsequent regeneration. Overall, the results of our study highlight the potential of all the D-π-A systems as promising sensitizers for DSSCs applications, owing to their favorable optical and electronic properties and impressive photovoltaic parameters.

Influence of acceptors on the optical nonlinearity of 5H-4-oxa-1,6,9-trithia-cyclopenta[b]-as-indacene-based chromophores with a push-pull assembly: a DFT approach

Herein, a series of compounds (TPD1-TPD6) having a D-π-A architecture was quantum chemically designed via the structural modulation of TPR. Quantum chemical calculations were employed to gain a comprehensive insight into the structural and optoelectronic properties of the designed molecules at the M06/6-311G(d,p) level. Interestingly, all the designed chromophores displayed narrow energy gaps (2.123-1.788 eV) and wider absorption spectra (λmax = 833.619-719.709 nm) with a bathochromic shift in comparison to the reference compound (λmax = 749.602 nm and Egap = 3.177 eV). Further, Egap values were utilized to evaluate global reactivity parameters (GRPs), which indicate that all the chromophores expressed higher softness (σ = 0.134-0.559 eV-1) and lower hardness (η = 4.155-4.543 eV) values than the reference chromophore. Efficient charge transfer from donors towards acceptors was noted through FMOs, which was also supported by DOS and TDM analyses. Overall, the TPD3 derivative exhibited a remarkable reduction in the HOMO-LUMO band gap (1.788 eV) with a red shift as λmax = 833.619 nm. Furthermore, it exhibited prominent linear and non-linear characteristics such as μtotal = 24.1731 D, 〈α〉 = 2.89 × 10-22 esu, and βtotal = 7.24 × 10-27 esu, among all derivatives. The above findings revealed that significant non-linear optical materials could be achieved through structural tailoring with studied efficient acceptors.

A computational insight into enhancement of photovoltaic properties of non-fullerene acceptors by end-group modulations in the structural framework of INPIC molecule

Improving the open circuit voltage is a major challenge for enhancing the overall efficiency of organic solar cells. Current work has concentrated on improving open-circuit voltage by designing new molecular frameworks from an INPIC molecule having a conjugated fused core. We modulated the structure by changing the terminal groups of the reference molecule (INPIC) with seven strong electron-withdrawing units. We investigated various optoelectronic attributes, charge transfer, and photovoltaic and geometrical parameters by compiling the B3LYP/6-31G(d,p) functional of the DFT approach. The optical absorption for modulated molecules ranges from 748.51 nm to 845.96 nm while showing higher oscillation strength than INPIC. At the same time, their impressive charge transport is attributed to their smaller excitation and exciton binding energy, higher electron/hole mobility, narrower band gap, and a more than 99 % intramolecular charge transfer. The larger dipole moments help in the dense interaction of acceptors with employed donor J61 which, in turn, improves charge transfer at the donor-acceptor interface. One of the triumphs that are difficult to get in organic molecules is success in achieving a higher open circuit voltage (VOC). Our conceptualized molecular frameworks of acceptors are featured with a notable VOC improvement in the range of 1.84-2.05 eV. Thus, the results of the current investigation pave the root for architecting the acceptor molecules with impressive optoelectrical properties that may be capable of providing high photovoltaic output. Thus these acceptors can be utilized for the development of advanced organic solar cells in future.

Theoretical study of the Tetraaminelithium and Tetraaminesodium molecules complexed with H-, Li- and Na- anions: static and dynamic NLO parameters

CONTEXT

This work focuses on the study of six molecules composed of the TetraAmineLithium (TALi+) and TetraAmineSodium (TANa+) structures linked with the anions H-, Li- and Na-. The NLO results obtained by these calculations showed significant values of static first hyperpolarizabilities (βtot) ranging from 8.74 * 10-30 to 691.99 * 10-30 esu. The two molecules TALi-Li and TALi-Na gave the highest values of static βtot equal to 563.20 and 691.99 * 10-30 esu respectively and static second hyperpolarizabilities (γav) of 680.02 and 779.05 * 10-35 esu. The highest dynamic first hyperpolarizabilities (β||) values are around 1474080.00 * 10-30 esu and 6,145,080.00 * 10-30 esu at 720 nm lasers and which are attributed to the two molecules TANa-Li and TANa-Na respectively. Four molecules have push-pull behavior where the anions are donor groups, the Li+-NH3 and Na+-NH3 groups are acceptor groups and a bridge composed by the three remaining NH3 ligands. The maximum wavelengths (λmax) in vacuum and in the presence of solvents for all molecules are in the range 240 to 870 nm.

METHOD

The software used in this study is Gaussian 16. The optimizations of the molecules were calculated by B3LYP-D3/6-31 +  + G(d,p). The static first hyperpolarizability (βtot) was calculated by different functionals: CAM-B3LYP, LC-wPBE, LC-BLYP, M11, wB97X, HSEh1PBE and M06-2X and the MP2 method, the basis-set used is 6-31 +  + G(d,p). Other calculations of static βtot were carried out by the CAM-B3LYP functional combined with several basis-sets: 6-31G(d,p), 6-31 +  + G(d,p), cc-pVDZ, AUG-cc- pVDZ, 6-311G(d,p), 6-311 +  + G(d,p), cc-pVTZ and AUG-cc-pVTZ. The calculations of the first (β||) and second (γ||) hyperpolarizabilities in second harmonic generation (SHG) were calculated by CAM-B3LYP/6-31 +  + G(d,p). The delocalization energies (E(2)) were determined by the NBO approach and calculated by the same functional and basis-set cited before. The solvation Gibbs energies (ΔGsolv) were calculated using the implicit SMD model. Maximum wavelengths (λmax) and oscillator strengths ([Formula: see text]) were calculated by TD-CAM-B3LYP/6-31 +  + G(d,p) in the presence of the implicit CPCM model.

Exploring the Electronic, Optical, and Charge Transfer Properties of A-D-A-Type IDTV-ThIC-Based Molecules To Enhance Photovoltaic Performance of Organic Solar Cells

Improving the charge mobility and optoelectronic properties of indacenodithiophene-based small molecule acceptors is a key challenge to improving overall efficiency. In this current research, seven newly designed molecules (DT1-DT7) comprising the indacenodithiophene-based core are presented to tune energy levels, enhance charge mobility, and improve the photovoltaic performance of IDTV-ThIC molecules via density functional theory. All the molecules were designed by end-capped modification by substituting terminal acceptors of IDTV-ThIC with strong electron-withdrawing moieties. Among all the examined structures, DT1 has proved itself a superior molecule in multiple aspects, including higher λmax in chloroform (787 nm) and gaseous phase (727 nm), narrow band gap (2.16 eV), higher electron affinity (3.31 eV), least excitation energy (1.57 eV), and improved charge mobility due to low reorganization energy and higher excited state lifetime (2.37 ns) when compared to the reference (IDTV-ThIC) and other molecules. DT5 also showed remarkable improvement in different parameters, such as the lowest exciton binding energy (0.41 eV), leading to easier charge moveability. The improved open-circuit voltage of DT4 and DT5 makes them proficient molecules exhibiting the charge transfer phenomenon. The enlightened outcomes of these molecules can pave a new route to develop efficient organic solar cell devices using these molecules, especially DT1, DT4, and DT5.

A comprehensive analysis of charge transfer effects on donor-pyrene (bridge)-acceptor systems using different substituents

The alternant polycyclic aromatic hydrocarbon pyrene has photophysical properties that can be tuned with different donor and acceptor substituents. Recently, a D (donor)-Pyrene (bridge)-A (acceptor) system, DPA, with the electron donor N,N-dimethylaniline (DMA), and the electron acceptor trifluoromethylphenyl (TFM), was investigated by means of time-resolved spectroscopic measurements (J. Phys. Chem. Lett. 2021, 12, 2226-2231). DPA shows great promise for potential applications in organic electronic devices. In this work, we used the ab initio second-order algebraic diagrammatic construction method ADC(2) to investigate the excited-state properties of a series of analogous DPA systems, including the originally synthesized DPAs. The additionally investigated substituents were amino, fluorine, and methoxy as donors and nitrile and nitro groups as acceptors. The focus of this work was on characterizing the lowest excited singlet states regarding charge transfer (CT) and local excitation (LE) characters. For the DMA-pyrene-TFM system, the ADC(2) calculations show two initial electronic states relevant for interpreting the photodynamics. The bright S1 state is locally excited within the pyrene moiety, and an S2 state is localized ~0.5 eV above S1 and characterized as a donor to pyrene CT state. HOMO and LUMO energies were employed to assess the efficiency of the DPA compounds for organic photovoltaics (OPVs). HOMO-LUMO and optical gaps were used to estimate power conversion and light-harvesting efficiencies for practical applications in organic solar cells. Considering the systems using smaller D/A substituents, compounds with the strong acceptor NO2 substituent group show enhanced CT and promising properties for use in OPVs. Some of the other compounds with small substituents are also found to be competitive in this regard.

Tuning the Photophysical Properties of Acceptor-Donor-Acceptor Di-2-(2-oxindolin-3-ylidene) Malononitrile Materials via Extended π-Conjugation: A Joint Experimental and Theoretical Study

Many optoelectronic applications require organic semiconductor (OSC) materials with high electron affinity. In this work, a series of novel acceptor-donor-acceptor (A-D-A) materials with low-lying LUMO energy levels were designed and characterized. In this strategy, two acceptor dyes, bis-isatin and di-2-(2-oxindolin-3-ylidene) malononitrile, were connected by various π-bridges (benzene ring, benzo[c][1,2,5]thiadiazole, monothiophene, trithiophene). We varied the length of the π-conjugation of the central core and the linkage position of the acceptor core (4- vs. 6-position of the phenyl ring) to investigate the effect on the optical and electrochemical properties of the materials. We performed density functional theory (DFT) and time-dependent DFT (TD-DFT) studies to gain insight into the dyes' electronic properties by determining the energy levels. Our findings demonstrate that with increasing acceptor strength and π-conjugation length of the core, the wavelength of the longest absorption maximum as well as their respective extinction coefficients are enhanced, which results in band-gap reduction either by lowering the LUMO and/or raising the HOMO energy level of the molecules. The potential practical utility of these materials as electron-transport materials for perovskite solar cells (PSCs) has been demonstrated.

Quantum Modification of Indacenodithieno[3,2-b]thiophene-Based Non-fullerene Acceptor Molecules for Organic Solar Cells of High Efficiency

In order to enhance the efficacy of organic solar cells, six new three-dimensional small donor molecules (IT-SM1 to IT-SM6) have been computationally designed by modifying the peripheral acceptors of the reference molecule (IT-SMR). The frontier molecular orbitals revealed that IT-SM2 to IT-SM5 had a smaller band gap (E_gap) than IT-SMR. They also had smaller excitation energies (E_x) and exhibited a bathochromic shift in their absorption maxima (λ_max) when compared to IT-SMR. In both the gas and chloroform phases, IT-SM2 had the largest dipole moment. IT-SM2 also had the best electron mobility, while IT-SM6 had the best hole mobility owing to their smallest reorganization energy for electron (0.1127 eV) and hole (0.0907 eV) mobility, respectively. The analyzed donor molecules' open-circuit voltage (V_OC) indicated that all of these proposed molecules had greater V_OC and fill factor (FF) values than the IT-SMR molecule. In accordance with the evidence of this work, the altered molecules can seem to be quite proficient for usage by experimentalists and have prospective use in future in the manufacture of organic solar cells with improved photovoltaic properties.

Tuning the optoelectronic properties of acridine-triphenylamine (ACR-TPA) based novel hole transporting material for high efficiency perovskite and organic solar cell

In this research, five distinct small donor molecules (designated as ACR-TPA-X1, ACR-TPA-X2, ACR-TPA-X3, ACR-TPA-X4, ACR-TPA-X5) are constructed by replacing the methoxy groups on both sides of the model molecule (ACR-TPA-R) with thiophene bridged acceptor moieties. We have used the B3LYP/6-31G (d,p) model for our computational studies. Our model molecule's morphological alteration has resulted in a lowered E_g of 1.77-2.51 eV as compared to model (ACR-TPA-R=3.84 eV). ACR-TPA-X2 investigated the λ_max at 776 nm. ACR-TPA-X4 was found to be most miscible with dichloromethane (DCM). The greatest V_OC(1.21 eV) was observed in ACR-TPA-X1. Among all of the variants, ACR-TPA-X1 had the highest PCE (23.42%). It was found that ACR-TPA-X4 had the highest electron mobility (0.00370 eV) and ACR-TPA-X5 had the highest hole mobility (0.00324 eV) of all the materials examined. The findings prove the worth of the methods used, paving the way for the development of effective small donors for OSCs and HTMs for PSCs.

Theoretical framework for achieving high V oc in non-fused non-fullerene terthiophene-based end-capped modified derivatives for potential applications in organic photovoltaics

Non-fused ring-based OSCs are an excellent choice, which is attributed to their low cost and flexibility in applications. However, developing efficient and stable non-fused ring-based OSCs is still a big challenge. In this work, with the intent to increase V _oc for enhanced performance, seven new molecules derived from a pre-existing A-D-A type A3T-5 molecule are proposed. Different important optical, electronic and efficiency-related attributes of molecules are studied using the DFT approach. It is discovered that newly devised molecules possess the optimum features required to construct proficient OSCs. They possess a small band gap ranging from 2.22-2.29 eV and planar geometries. Six of seven newly proposed molecules have less excitation energy, a higher absorption coefficient and higher dipole moment than A3T-5 in both gaseous and solvent phases. The A3T-7 molecule exhibited the maximum improvement in optoelectronic properties showing the highest λ _max at 697 nm and the lowest E _x of 1.77 eV. The proposed molecules have lower ionization potential values, reorganization energies of electrons and interaction coefficients than the A3T-5 molecule. The V _oc of six newly developed molecules is higher (V _oc ranging from 1.46-1.72 eV) than that of A3T-5 (V _oc = 1.55 eV). Similarly, almost all the proposed molecules except W6 exhibited improvement in fill factor compared to the A3T-5 reference. This remarkable improvement in efficiency-associated parameters (V _oc and FF) proves that these molecules can be successfully used as an advanced version of terthiophene-based OSCs in the future.

Alteration of the central core of a DF-PCIC chromophore to boost the photovoltaic applications of non-fullerene acceptor based organic solar cells

Modifying the central core is a very efficient strategy to boost the performance of non-fullerene acceptors. Herein five non-fullerene acceptors (M1-M5) of A-D-D'-D-A type were designed by substituting the central acceptor core of the reference (A-D-A'-D-A type) with different strongly conjugated and electron donating cores (D') to enhance the photovoltaic attributes of OSCs. All the newly designed molecules were analyzed through quantum mechanical simulations to compute their optoelectronic, geometrical, and photovoltaic parameters and compare them to the reference. Theoretical simulations of all the structures were carried out through different functionals with a carefully selected 6-31G(d,p) basis set. Absorption spectra, charge mobility, dynamics of excitons, distribution pattern of electron density, reorganization energies, transition density matrices, natural transition orbitals and frontier molecular orbitals, respectively of the studied molecules were evaluated at this functional. Among the designed structures in various functionals, M5 showed the most improved optoelectronic properties, such as the lowest band gap (2.18 e V), highest maximum absorption (720 nm), and lowest binding energy (0.46 eV) in chloroform solvent. Although the highest photovoltaic aptitude as acceptors at the interface was perceived to be of M1, its highest band gap and lowest absorption maxima lowered its candidature as the best molecule. Thus, M5 with its lowest electron reorganization energy, highest light harvesting efficiency, and promising open-circuit voltage (better than the reference), amongst other favorable features, outperformed the others. Conclusively, each evaluated property commends the aptness of designed structures to augment the power conversion efficiency (PCE) in the field of optoelectronics in one way or another, which reveals that a central un-fused core having an electron-donating capability with terminal groups being significantly electron withdrawing, is an effective configuration for the attainment of promising optoelectronic parameters, and thus the proposed molecules could be utilized in future NFAs.

Quantum modeling of dimethoxyl-indaceno dithiophene based acceptors for the development of semiconducting acceptors with outstanding photovoltaic potential

In the current DFT study, seven dimethoxyl-indaceno dithiophene based semiconducting acceptor molecules (ID1-ID7) are designed computationally by modifying the parent molecule (IDR). Here, based on a DFT exploration at a carefully selected level of theory, we have compiled a list of the optoelectronic properties of ID1-ID7 and IDR. In light of these results, all newly designed molecules, except ID5 have shown a bathochromic shift in their highest absorbance (λ _max). ID1-ID4, ID6 and ID7 molecules have smaller band gap (E _gap) and excitation energy (E _x). IP of ID5 is the smallest and EA of ID1 is the largest among all others. Compared to the parent molecule, ID1-ID3 have increased electron mobility, with ID1 being the most improved in hole mobility. ID4 had the best light harvesting efficiency in this investigation, due to its strongest oscillator. The acceptor molecules' open-circuit voltages (V _OC) were computed after being linked to the PTB7-Th donor molecule. Fill factor (FF) and normalized V _OC of ID1-ID7 were calculated and compared to the parent molecule. Based on the outcomes of this study, the modified acceptors may be further scrutinised for empirical usage in the production of organic solar cells with enhanced photovoltaic capabilities.

Impact of end-capped modification of MO-IDT based non-fullerene small molecule acceptors to improve the photovoltaic properties of organic solar cells

Density functional theory, along with its time dependent computational approach were employed in order to fine tune the photovoltaic attributes along with the efficiency of the MO-IDIC-2F molecule. Thus, five new molecules were designed by substitution of the different notable acceptor fragments in the MO-IDIC-2F molecule, along with the addition of the "[1, 2, 5] thiadiazolo[3,4-d] pyridazine" spacer moieties between donor core and newly substituted acceptor groups. In this research work, various photovoltaic properties, which could affect the efficiency of an organic chromophores, such as bandgap, oscillator strength, dipole moment, binding energy, light-harvesting efficiency, etc. were studied. All the newly proposed molecules demonstrated significantly improved outcomes in comparison to that of the reference molecule, in their absorption spectrum, excitation, as well as binding energy values, etc. In order to confirm the results of optoelectronic properties, density of states, transition density matrix, and electrostatic potential analyses of molecules were also performed, which supported our computational findings. All of the results confirmed the high potential of all the newly proposed molecules for the development of improved OSCs.

Theoretical investigation by DFT and TDDFT the extension of π-conjugation of novel carbazole-based donor materials for bulk heterojunction organic solar cell applications

In this study, we have proposed seven designed symmetrical compounds (C₂-C₈) having a D-π-A-π-D structure based on derivative carbazole as a donor by introducing various π-spacer groups into the reference compound C₁-Ref having a D-A-D structure in order to understand the influence of different π-spacers on their efficiency in BHJ solar cells. Various parameters such as geometrical structures, frontier molecular orbitals (FMOs), molecular electrostatic potential (MEP), nonlinear optical properties (NLO), optical properties, light-harvesting efficiency (LHE), reorganization energy, chemical reactivity indices, exciton binding energy (E_b), open-circuit voltage (V_OC), and fill-factor (FF) have been investigated using the density functional theory (DFT) and time-dependent DFT (TD-DFT) methods. The results show that the extended π-conjugation of the designed compounds (C₂-C₈) produces a lower energy gap (E_g), a stronger and broader absorption spectrum, lower reorganization energies and exciton binding, and higher nonlinear optical properties compared to C₁-Ref, indicating that these designed compounds are promising as electron donors in BHJ-OSCs. Additionally, the calculated V_oc, FF, and LHE of all compounds showed that the C₂, C₃, C₄, C₅, and C₇ compounds have the best performance in BHJ solar cells compared to the others. In particular, C₄ and C₅ are excellent candidates for the effective donor materials of BHJ solar cells due to their large V_oc, FF, and LHE than the other compounds. This theoretical investigation is expected to provide new strategies to synthesize efficient donor materials for BHJ-OSCs.

Designing dibenzosilole core based, A2-π-A1-π-D-π-A1-π-A2 type donor molecules for promising photovoltaic parameters in organic photovoltaic cells

In this research work, four new molecules from the π-A-π-D-π-A-π type reference molecule "DBS-2PP", were designed for their potential application in organic solar cells by adding peripheral A2 acceptors to the reference. Under density functional theory, a comprehensive theoretical investigation was conducted to examine the structural geometries, along with the optical and photovoltaic parameters; comprising frontier molecular orbitals, density of states, light-harvesting effectiveness, excitation, binding, and reorganizational energies, molar absorption coefficient, dipole moment, as well as transition density matrix of all the molecules under study. In addition, some photo-voltaic characteristics (open circuit photo-voltage and fill factor) were also studied for these molecules. Although all the developed compounds (D1-D4) surpassed the reference molecule in the attributes mentioned above, D4 proved to be the best. D4 possessed the narrowest band-gap, as well as the highest absorption maxima and dipole moment of all the molecules in both the evaluated phases. Moreover, with PC61BM as the acceptor, D4 showed the maximum V OC and FF values. Furthermore, while D3 had the greatest hole mobility owing to its lowest value of hole reorganization energy, D4 exhibited the maximum electron mobility due to its lowermost value of electron reorganization energy. Overall, all the chromophores proposed in this study showed outstanding structural, optical, and photovoltaic features. Considering this, organic solar cell fabrication can be improved by using these newly derived donors at the donor-acceptor interfaces.

Quantum chemical modification of indaceno dithiophene-based small acceptor molecules with enhanced photovoltaic aspects for highly efficient organic solar cells

In this computational work, with the aim of boosting the ultimate efficiency of organic photovoltaic cells, seven small acceptors (IDST1-IDST7) were proposed by altering the terminal-acceptors of reference molecule IDSTR. The optoelectronic characteristics of the IDSTR and IDST1-IDST7 molecules were investigated using the MPW1PW91/6-31G(d,p) level of theory, and solvent-state computations were examined using time-dependent density functional theory (TD-DFT) simulation. Nearly all the investigated photovoltaic aspects of the newly proposed molecules were found to be better than those of the IDSTR molecule e.g. in comparison to IDSTR, IDST1-IDST7 exhibit a narrower bandgap (E _gap), lower first excitation energy (E _x), and a significant red-shift in the absorbance maxima (λ _max). According to the findings, IDST3 has the lowest E _x (1.61 eV), the greatest λ _max (770 nm), and the shortest E _gap (2.09 eV). IDST1-IDST7 molecules have higher electron mobility because their RE of electrons is less than that of IDSTR. Hole mobility of IDST2-IDST7 is higher than that of the reference owing to their lower RE for hole mobility than IDSTR. By coupling with the PTB7-Th donor, the open circuit voltage (V _OC) of the investigated acceptor molecules (IDSTR and IDST1-IDST7) was calculated and investigation revealed that IDST4-IDST6 molecules showed higher V _OC and fill factor (FF) values than IDSTR molecules. Accordingly, the modified molecules can be seriously evaluated for actual use in the fabrication of OSCs with enhanced photovoltaic and optoelectronic characteristics in light of the findings of this study.

Engineering of W-shaped benzodithiophenedione-based small molecular acceptors with improved optoelectronic properties for high efficiency organic solar cells

In the current study, with the objective to improve the overall performance of organic solar cells, seven new W-shaped small molecular acceptors – were developed theoretically by the end-group alteration of the reference (WR) molecule. The MPW1PW91 functional with the basis set 6-31G(d,p) was used to explore the optoelectronic properties of the WR and W1–W7 molecules and the time-dependent self-consistent filed (TD-SCF) simulation was used to investigate the solvent-state calculations. The several explored photovoltaic attributes were the absorption spectra, excitation energies, bandgap between the FMOs, oscillator strength, full width at half maximum, light-harvesting efficiency, transition density matrices, open-circuit voltage, fill factor, density of states, binding energy, interaction coefficient, etc. Overall, the results revealed a bathochromic shift in the absorption maxima (λ_max), a reduced HOMO–LUMO gap (E_gap), and smaller excitation energy (E_x) of the altered molecules as compared to the WR molecule. Some of the optoelectronic aspects of a well-known fused ring based acceptor named Y6 are also compared with the studied W-shaped molecules. Additionally, the W1 molecule presented the smallest E_gap, along with highest λ_max and the lowest E_x, amongst all, in both the evaluated media (gas and solvent). The open circuit voltage (V_OC) of all the considered small molecular acceptors was calculated by pairing them with the PTB7-Th donor. Here, W6 and W7 displayed the best results for the V_OC (1.48 eV and 1.51 eV), normalized V_OC (57.25 and 58.41) and FF (0.9131 and 0.9144). Consequently, in light of the results of this research, the altered molecules could be considered for practical implementation in the manufacturing of OSCs with improved photovoltaic capabilities.

The developed molecules have a reduced band gap and lower excitation energy. Their V_OC was calculated by making complexes of them with the PTB7-Th donor.

Spirothienoquinoline-based acceptor molecular systems for organic solar cell applications: DFT investigation

In this research, eight three-dimensional benzothiadiazole and spirothienoquinoline-based donor molecules of the A-D-A-D-A configuration were formulated by introducing new acceptor groups (A1-A4) to the terminal sites of recently synthesized potent donor molecule (^tBuSAF-Th-BT-Th-^tBuSAF). Frontier molecular orbital analysis, reorganization energies, the density of states analysis, transition density matrix analysis, dipole moment, open-circuit voltage, and some photophysical properties were all assessed using CAMB3LYP/LanL2DZ. The optoelectronic properties of freshly proposed compounds were compared to the reference molecule (SQR). Due to the existence of robust electron-attracting acceptor moiety, SQM3 and SQM7 had the greatest maximum absorption of all other investigated molecules, with the values of 534 and 536 nm, respectively. The maximum dipole moment, narrow bandgap (3.81 eV and 3.66 eV), and HOMO energies (- 5.92 eV, 5.95 eV) are also found in SQM3 and SQM7, respectively. The SQM3 molecule also possesses the least reorganization energy for hole mobility (0.007237 eV) than all other considered molecules. The open-circuit voltage of all the molecules considered to be donors, was calculated with respect to PC₆₁BM and it is estimated that except SQM7 and SQM3 all other newly developed molecules have improved open-circuit voltage. The findings show that most of the designed donor molecules can perform better experimentally and should be employed for practical implementations in the future.

Nonfullerene Near-Infrared Sensitive Acceptors "Octacyclic Naphtho[1,2-b:5,6-b] Dithiophene Core" for Organic Solar Cell Applications: In Silico Molecular Engineering

End-capped modification is an efficient approach for enhancing the power conversion efficiency of organic solar cells (OSCs). Herein, five novel acceptor molecules have been designed by end-capper modification of the recently synthesized molecule NTIC (R). Different geometric and photovoltaic properties like frontier molecular orbital analysis, absorption maximum, transition density matrix analysis, reorganizational energy, binding energy, oscillator strength, energy of excitation, and charge transfer analysis of designed and reference molecules have been computed by employing density functional theory and time-dependent density functional theory. Designed molecules expressed a narrow energy band gap (E _g) with red-shifting in the absorption spectrum. Additionally, low excitation and binding energies are also noted in designed molecules. Excellent values of hole and electron reorganizational energies suggested that designed molecules are effective contributors to the development of the active layer of the organic solar cells. Further, a complex study is also performed for evaluation of charge transfer between the acceptor molecule and the donor polymer. Results of all analyses recommended that designed molecules are effective candidates for high-performance organic solar cell applications.

Symmetrical end-capped molecular engineering of star-shaped triphenylamine-based derivatives having remarkable photovoltaic properties for efficient organic solar cells

In the present research work, four novel triphenylamine (TPA)-based acceptor molecules have been architectured to step up the solar efficiency of organic solar cells. The four designed molecules abbreviated as T1-T4 have a common TPA donor core and different strong electron pulling peripheral acceptor groups connected through thiophene spacers. Computational simulations of T1-T4 were performed to compute and compare their optoelectronic properties with well-known reference molecule S(TPA-DPP) designated as R in the current project. For geometric optimizations of designed molecules, MPW1PW91 functional along with a basis set of 6-31G (d, p) was enforced. Assessment of the optoelectronic features of newly reported 3-D molecules (T1-T4) has been executed through density functional theory (DFT) and time-dependent density functional theory (TD-DFT) computations. Transition density matrix (TDM) and density of state (DOS) evaluations were performed for the investigation of exciton dynamics and electronic contribution between two states. All the derived molecules exhibited admirable photovoltaic features when compared to that of the reference molecule. Amidst all these newly modified molecules, T3 manifested itself as the finest candidate having the least energy band gap (1.84 eV) and the highest λ_max (865 nm) in dichloromethane solvent. Also, T1 molecule has the lowest hole reorganization energy (0.0036 eV) value. These designed candidates (T1-T4) confirm that peripheral acceptor tempering is an effectual approach for the attainment of the desirable optoelectronic properties.

Synergistic end-capped engineering on non-fused thiophene ring-based acceptors to enhance the photovoltaic properties of organic solar cells

In this study, a series of non-fused thiophene ring-based small molecular acceptors (4T1-4T7) of A-D-A type are developed by the replacement of the end-groups of the 4TR molecule. The optoelectronic characteristics of the 4TR and 4T1-4T7 molecules are investigated employing the MPW1PW91 functional with the 6-31G (d,p) basis set, and solvent-state computations are studied using the TD-SCF. All the parameters estimated in this research are improved to a substantial level for the developed molecules as compared to the 4TR molecule, e.g. all the newly developed molecules have shown a red shift in their maximum absorption (λ max) and a reduced bandgap compared to the 4TR molecule, with ranges of 646 nm to 692 nm (in chlorobenzene solvent) and 2.34 eV to 2.47 eV, respectively. The reorganization energies of electron and hole mobility for almost all developed molecules are smaller than those for the 4TR molecule, with ranges of 0.00766-0.01034 eV and 0.01324-0.01447 eV, respectively. Hence, all the modified chromophores exhibit better charge capabilities than the 4TR molecule. The charge mobility of almost all the developed molecules is improved because of their reduced reorganization energies. The 4T2 molecule has minimum RE values for both electrons (0.00766) and holes (0.01324). The V OC values of all acceptor molecules are calculated with respect to the PTB7-Th donor. An elevation in V OC and FF values is exhibited by the 4T5 and 4T7 molecules. As a result, these end-capped engineered molecules should be proposed for the future manufacturing of highly efficient organic solar cells.