End-capped Acceptor Research Articles

Quantum chemical study of end-capped acceptor and bridge on triphenyl diamine based molecules to enhance the optoelectronic properties of organic solar cells

This research project focuses on quantum chemical study of triphenyl diamine based molecules and DFT analysis of reference XSln847 and nine designed molecules to boost the efficiencies of organic solar cells and to make viable competitive solar cell. To study photovoltaic features, computational DFT and TD-DFT simulations are used to conduct extensive research at the molecular level of the investigated compounds. CAM-B3LYP/6-31G (d, p) level has been used to perceive molecules analytically for their predicted values of absorption maximum, highest light harvesting efficiency, frontier molecular orbitals and quantum chemical parameters i.e. chemical potential, chemical softness, chemical hardness, and electrophilicity index. Amongst TPDM-1 to TPDM-9 structures, TPDM-9 shows maximum absorption (530 nm) and lowest bandgap (3.19 eV). TPDM-7 has highest power conversion efficiency. While TPDM-4 shows better light harvesting efficiency to enhance organic solar cells efficiency. After successfully verifying the compatibility of the donor and acceptor interfaces, the PTB7-Th (donor) is used for electrophilic designed molecules while for donor designed molecules PC16BM (acceptor) is used as their HOMO LUMO values for the estimation of Voc values. All the proposed molecules show computationally amplified metrics, which is a compelling argument for their potential experimental use in creating effective solar cells.

Tuning the optoelectronic properties of indacenodithiophene based derivatives for efficient photovoltaic applications: A DFT approach

In this study, five novel push-pull acceptor molecules with A-B-D-B-A arrangement have been formulated in the quest to boost the organic solar cells (OSCs), with respect to their electrical, optical, and chemical characteristics. Substitution of end-capped acceptor moieties in non-fullerene materials is an effective approach of molecular modeling, which finely tunes the optoelectronic attributes of OSCs. The recently altered molecules (Y1-Y5) were flanked with different electron withdrawing units carrying indacenodithiophene (IDT) as the central electron donating core. The density functional theory (DFT) and time-dependent density functional theory (TD-DFT) analysis were executed at B3LYP functional with 6-31G (d,p) basis set to investigate the geometrical as well as optical parameters such as quantum mechanical descriptors, light harvesting efficiency, ionization potential energy, absorption properties, electron affinity, dipole moment, molecular electrostatic potential, transition density matrix, the density of states, and reorganization energies. All of these studied molecules revealed greater electronic transitions, superior optical properties, fast charge mobilities, and better solubility in the polar solvent when compared to the reference molecule. Amongst all these derived molecules, Y1 emerged as a distinctive candidate, exhibiting the highest maximum absorption wavelength (884 nm) in chloroform along with the smallest energy gap (1.72 eV) as well as the lowest optical gap (1.40 eV). Moreover, it has the highest electron affinity and ionization potential energy, least interaction coefficient, exciton binding energy, and reorganization energy (λe = 0.00340 eV), which can be ascribed to its potent electron withdrawing moieties, which intensifies the transfer of charge between the donor and acceptor units within a molecule. We expect these modifications in the terminal groups around the central core to provide strong theoretical strategies to construct and amplify the photovoltaic parameters of OSCs in the future.

Exploration of the interesting photovoltaic behavior of the fused benzothiophene dioxide moiety as a core donor with modification in acceptors for high-efficacy organic solar cells.

Non-fullerene-based chromophores with end-capped acceptor modification used in organic solar cells (OSCs) have proven to offer improved performance. Therefore, eight unique benzothiophene-based molecules (D2-D9) were designed by the end-capped acceptor manipulation of a reference molecule (R1). Density functional theory (DFT) and time-dependent density functional theory (TD-DFT) calculations at the B3LYP level were performed to investigate various parameters such as the optical properties, frontier molecular orbitals (FMOs), transition density matrix (TDM), binding energy, density of states (DOS), open-circuit voltage (V oc), and reorganization energies of electrons (λ e) and holes (λ h), to better understand the optoelectronic properties of the newly designed compounds. All the derivatives had broader absorption spectra of 737.562-700.555 nm with a reduced energy gap of 2.132-1.851 eV compared to those of the reference (719.082 nm), except for D8 and D9. A comparable value of V oc and lower reorganization energies were found in the derivatives compared to those of R1. Within the studied compounds, D3 was predicted to be a good optoelectronic material for environmentally friendly organic solar cells (EFOSCs) because of its superior optoelectronic capabilities, low-energy band gap (1.851 eV), highest λ max values of 794.516 and 744.784 nm in chloroform and the gas phase, respectively, and lowest transition energy (1.561 eV) than those of the reference and the other derivatives. Subsequently, end-capped acceptor modification was proven to be an effective method to achieve desired optoelectronic characteristics.

Synergistic engineering of end-capped acceptor and bridge on arylborane-arylamine macrocycles to boost the photovoltaic properties of organic solar cells

A new stream of donor- π -acceptor (D- π -A) type arylborane-arylamine based donor contributors namely (BN1, BN2, BN3, BN4, BN5) have been drafted by substituting the terminal 2,4,6-tris-(trifluoromethyl)phenyl groups of reference B4N2-FMes (designated as BNR in the current study) with thiophene followed by W1 (4-(5-methylthiophen-2-yl)benzothiadiazole), W2 (2-(3-methyl-5-methylene-4-oxothiazolidin-2-ylidene)malononitrile), W3 (3-methyl-5-methylene-2-thioxothiazolidin-4-one), W4 (2-methylenemalononitrile), W5 (2-cyanoacrylicaidmethylester) acceptor moieties respectively. The computational characterization was performed via reliable density functional theory at B3LYP/6–31G (d,p). The optoelectronic parameters of newly planned molecules have been cross-checked with the reference (BNR). The newly planned (BN1-BN5) conjugated macrocycles have manifested outperformed results. Amongst all, BN4 has displayed the lowest band gap (2.07 eV), highest λmax (672 nm) in dichloromethane (DCM), highest ionization potential (IP) and electron affinity (EA) owing to its functionalization with cyano (CN) containing strong electron pulling moieties. Out of all reported molecules, BN1 has explored the lowest reorganization energy (RE) value for the electron (λ- = 0.00224 eV) and hole (λ+ = 0.00266 eV) demonstrating its augmented charge transition. BN1 is characterized by the highest dipole moment (6.31 D) in DCM addressing its enhanced solubility. Amongst all, BN4 has explored the highest VOC (1.51 eV) due to its low-lying HOMO. To sum up, the thiophene bridged end-capped acceptor alteration approach has been proved persuasive in providing the gateway to devise optimistic photovoltaic materials. All currently planned donor contributors (BN1-BN5) ought to be targeted to assemble upcoming proficient organic solar cells (OSCs).

DFT analysis of different substitutions on optoelectronic properties of carbazole-based small acceptor materials for Organic Photovoltaics

In this present study, we have investigated a series of six new novels A-π-D-π-A type small non-fullerene acceptor molecules to enhance the efficiency of organic solar cells. The designed acceptors consist of carbazole moiety as donor (central core) and 3-ethylrhodanine moiety as end-capped acceptor group which is linked via different conjugated π-linkers namely benzo[c][1,2,5]thiadiazole, benzo[c][1,2,5]oxadiazole, thiophene, furan, and [1,2,5]oxadiazolo[3,4-c]pyridine. DFT (HSE06) and TD-DFT (M05) calculations have been carried out with 6-311G(d,p) basis set to investigate the effect of different π-linkers on the charge transfer rate, stability, and optoelectronic properties. Different π-linkers have resulted in smaller HOMO-LUMO energy gap as compared to reference. All investigated molecules M1, M2, M4, M5 and M6 have shown significant bathochromic shift of 31, 12, 92, 78 and 47 nm compared to R except M3 which has shown slightly blue shift of 22 nm, respectively. The reorganization energy analysis predicted the ambipolar behavior of designed molecules. Molecular electrostatic potential maps (MEP), the density of state (DOS), and electron density difference maps (EDDM) analysis have shown the stability parameters and confirmed the higher charge transfer between different fragments within the designed molecules. Thusly, energy level analysis indicates that designed molecules M1, M2, M4 and M5 could act as suitable non-fullerenes acceptors with previously designed PffBT4T-2OD donor for practical solar cells applications.

Exploration of efficient electron acceptors for organic solar cells: rational design of indacenodithiophene based non-fullerene compounds

The global need for renewable sources of energy has compelled researchers to explore new sources and improve the efficiency of the existing technologies. Solar energy is considered to be one of the best options to resolve climate and energy crises because of its long-term stability and pollution free energy production. Herein, we have synthesized a small acceptor compound (TPDR) and have utilized for rational designing of non-fullerene chromophores (TPD1–TPD6) using end-capped manipulation in A2–A1–D–A1–A2 configuration. The quantum chemical study (DFT/TD-DFT) was used to characterize the effect of end group redistribution through frontier molecular orbital (FMO), optical absorption, reorganization energy, open circuit voltage (Voc), photovoltaic properties and intermolecular charge transfer for the designed compounds. FMO data exhibited that TPD5 had the least ΔE (1.71 eV) with highest maximum absorption (λmax) among all compounds due to the four cyano groups as the end-capped acceptor moieties. The reorganization energies of TPD1–TPD6 hinted at credible electron transportation due to the lower values of λe than λh. Furthermore, open circuit voltage (Voc) values showed similar amplitude for all compounds including parent chromophore, except TPD4 and TPD5 compounds. These designed compounds with unique end group acceptors have the potential to be used as novel fabrication materials for energy devices.

Deciphering the role of end-capped acceptor units for amplifying the photovoltaic properties of donor materials for high-performance organic solar cell applications

Non-fullerene organic solar cells (OSCs) deliver the highest efficiency gains overall in reported literature. Efforts are being made to refine efficacies and stabilities of organic solar cells through the designing of acceptor molecules that contain powerful electron-withdrawing groups. Here, we computed four acceptors (Y1-Y4) by end-capped alterations on reference R and optimize photophysical, optoelectronic and photovoltaic properties. Therefore, certain properties such as orientation of FMO’s, excitation and binding energy, open-circuit voltage (Voc), transition density matrix and reorganizational energy of hole and electron are observed in comparison with reference. The calculated molecular structures of Y1 and Y4 show a high red-shift, while that of Y2 and Y3 display slightly blue-shift, along with very fine excitation energies and high charge mobilities. All these molecules (Y1-Y4) and the reference R presents band-gaps as small as 1.5–2.5 eV, and considerable charge transfer potential. This theoretical system shows that end-capped acceptors alteration is quite remarkable to establish desired optoelectronic properties. Thus, Y1-Y4 are suggested to researchers aiming at the potential commercialization of highly efficient solar cells systems.

Tuning the optoelectronic properties of benzodithiophene based donor materials and their photovoltaic applications

To improve the quantum efficiency and device performance of OSCs, four new BDTS-2DPP based donor molecules were designed, flanked with variable non-fullerene end-capped acceptor units namely, 2-methylenemalanonitrile (BDTS1), methyl 2-cyanoacrylate (BDTS2), 2-(5,6-difluoro-2-methylene-3-oxo-2,3-dihydroinden-1-ylidene)malononitrile (BDTS3), and 3-methyl-5-methylene-2-thioxothiazolidin-4-one (BDTS4). A detailed computational study was carried out on designed molecules using DFT and TD-DFT to examine their optoelectronic properties. Optical parameters such as maximum absorption, dipole moments, excitation energies, etc. were recorded at excited optimized states using dichloromethane solvent. Next, to analyze the charge density distribution and energy level differences, DOS and FMOs were interpreted. Reorganization energies were calculated to find out electron-hole mobilities and exciton coherence is indicated by TDM maps. The results illustrate that these molecules (BDTS1-BDTS4) excelled the reference molecule in all the computed properties. BDTS3 exhibited the highest λmax (865 nm) and least band gap (1.80 eV) while BDTS1 endured the highest electron-hole mobilities and open-circuit voltage (1.61 eV). All the theoretically computed parameters suggest that these designed molecules could be used as proficient donor materials in OSCs.

Quantum Chemical Approach of Donor−π–Acceptor Based Arylborane–Arylamine Macrocycles with Outstanding Photovoltaic Properties Toward High-Performance Organic Solar Cells

A theoretical quantum chemical investigation of D−π–A conjugated molecules based on arylborane–arylamine is proposed with the motive of suggesting new organic materials for organic solar cells (OSCs). Optoelectronic properties and geometries of organic donor molecules MC1R–MC1M5 encompassing a caged ring as the donor, thiophene as the bridge, and end-capped moieties as the acceptor are characterized using DFT and TD-DFT. Study involved forecasting the photophysical descriptors such as frontier molecular orbitals, ionization potential, electron affinity, molecular electrostatic potential, transition density matrix, binding energy (Eb), dipole moment, reorganization energy, and open-circuit voltage (VOC) at ground state geometries using the MPW1PW91/6-31G(d,p) basis set. By modulation of end-capped acceptor groups, comprehensive analysis of newly tailored molecules is conducted to reveal insight about π-conjugation contribution on the performance of OSCs. The structure–property relationship of the reference (MC1R) is contrasted with newly organized molecules (MC1M1–MC1M5). The proposed strategy effectively enhanced the absorption (λmax) of all designed molecules. MC1M1 exhibited λmax at 530 nm in DCM (dichloromethane) solvent with the lowest band gap (2.86 eV) and lowest excitation energy of 2.34 eV. An elevated VOC of 2.27 eV is revealed by MC1M4. MC1M2 presented a lowest binding energy of 0.42 eV. The highest hole and electron mobility is ascertained in all newly designed molecules because of their low reorganization energy values which validated preferrable photovoltaic properties as compared to the reference MC1R. MC1M1 showed the lowest electron mobility (λe = 0.009301 eV), and MC1M2 demonstrated the lowest hole mobility (λh = 0.001 874 eV). Our comparative outcomes are proposed to be possible choices for designing efficient OSCs.

Efficient tuning of small acceptor chromophores with A1-π-A2-π-A1 configuration for high efficacy of organic solar cells via end group manipulation

Now a days, non-fullerene organic compounds are considered with keen interest for the greener energy and potential photovoltaic devices. Herein, novel acceptor chromophores (DPDVD1-DPDVD4) were designed via small acceptor DPDVR compound with A1-π-A2-π-A1 architecture using promising approach by redistribution of end-capped acceptor moieties. The effect of end-capped acceptor moieties on designed architecture for the photophysical, photovoltaic and electronic behavior was explored using quantum chemical study. Frontier molecular orbital (FMO) findings revealed that all the molecules (DPDVD1-DPDVD4) contained narrow band gaps. The central acceptor moiety (PzDP) was responsible for the transformation of charge in DPDVD1-DPDVD4. UV–Vis data disclosed that λmax values of DPDVD1-DPDVD4 compounds were existed in visible region (537.36–517.05 nm). Interestingly, DPDVD2 exhibited the reduced band gap with broader absorption spectra among all chromophores might be due to the negative inductive effect (−I) of the terminal acceptors. The open circuit voltage (Voc) analysis was performed at the interface between standard donor polymer (PTB7) and DPDVD2. The higher value (3.34 V) of Voc was observed for DPDVD2 among reference and designed compounds. Furthermore, reorganization energy findings exploited DPDVR-DPDVD4 shown lower values of λe than λh which indicated that these chromophores were the promising candidates for electron transportation mobilities. The larger charge mobilities with greater exciton dissociation in excited state for DPDVD2 were examined, subsequently this compound showed minimum value of λe (0.015739 eV) among all chromophores. Detailed studies reveal that the entitled molecules can behave as efficient electron acceptor molecules in organic solar cells (OSCs) that make them interesting candidates for the development of inexpensive optoelectronic devices.

Computational and theoretical study of subphthalocyanine based derivatives by varying acceptors to increase the efficiency of organic solar cells

To enhance power conversion efficiency (PCE) of organic solar cells, four new small molecules were designed with subphthalocyanines (SubPc) as a common donor and different benzene bridged end-capped acceptor groups named as prop-1-yne (X1), 1,2,3,4,5-pentaflouro-6-methoxycyclohexane (X2), benzene-1,2,4,5-tetracarbonitrile (X3), and 1,2-diphenylethyne (X4). Photovoltaic effect and quantum parameters of X1-X4 were computed through DFT and TD-DFT by using a selected hybrid functional B3LYP at 6-31G (d, p). Opto-electronic properties such as, absorption maxima (λmax), band gap, charge mobilities and exciton dynamics of X1-X4 were characterized by analyzing the UV–Visible absorption spectra, frontier molecular orbitals (FMOs), reorganization energies and transition density matrix (TDM), respectively. The computed parameters of all the designed molecules were found to be more efficient than reference molecule R. Among all the designed molecules, the molecule X3 has highest absorption (λmax) at 562 nm, reduced band gap (2.07 eV), least reorganization energies of electrons (λe = 0.00462), hole (λh = 0.00232), better charge delocalization in Transition density matrix analysis, and maximum open-cicuit voltage (Voc) of 1.87 eV as compared with other molecules while least exciton binding energy is exhibited by X1 (0.295 eV). These results indicate that our designed molecules are promising donor materials in improving the device performance of OSCs.

Designing of benzodithiophene (BDT) based non-fullerene small molecules with favorable optoelectronic properties for proficient organic solar cells

To extinguish the thirst of extraordinary tailback in the stock of energy and to jack up the operational effectiveness of organic solar cells, 5 new donor molecules namely BDTM1, BDTM2, BDTM3, BDTM4, BDTM5 have been designed by the structural tailoring of the already experimentally synthesized POBDT-4Cl. POBDT-4Cl is taken as a reference designated as BDTR. All the designed chromophores constitute benzodithiophene as donor and thiophene bridged end-capped (3-methyl-5-methylene-2-thioxothiazolidin-4-one) BDTM1, (2-methylenemalononitrile) BDTM2, (methyl 2-cyanoacrylate) BDTM3, (2-(3-methyl-5-methylene-4-oxothiazolidin-2-ylidene)malononitrile) BDTM4, (4-(5-methylthiophen-2-yl)benzo[c][1,2,5]thiadiazole) BDTM5 acceptor groups. Influence of different terminal acceptor moieties on the molecular orbitals, density of states (DOS), maximum absorption (λmax), energy required for the generation of electron and hole carrier, transition density matrix (TDM), dipole moment, reorganization energy (RE), and open-circuit voltage (VOC) has been inquired via density-functional theory (DFT) and time-dependent density functional theory (TDDFT) methodology using B3LYP/6-31G (d,p) and these afore-mentioned features of newly devised molecules have been compared with the reference (BDTR). Among all newly designed molecules (BDTM1-BDTM5), BDTM1 exhibited the highest λmax value of 725 nm. BDTM3, BDTM4, and BDTM5 have displayed the highest dipole moment than the reference (BDTR). Cation (hole) transport rate of BDTM5 (0.00578 eV) and BDTM2 (0.00632 eV) has been explored lower than BDTR (0.00662 eV). Similarly, BDTM5 has displayed lower anion (electron) transport rate (0.00578 eV) relative to BDTR (0.00603 eV). Among all designed molecules, BDTM5 has expressed formidable and unique results accompanied by the lowest band gap (1.90 eV), comparable λmax (720 nm), and VOC. All newly constructed molecules have exposed enhanced VOC. Briefly, the thiophene bridged end-capped acceptor modification approach has been demonstrated compelling in providing the door to plan profoundly effective photovoltaic materials accompanied by exquisite optoelectronic parameters.

Synergistic effects of fluorine, chlorine and bromine-substituted end-capped acceptor materials for highly efficient organic solar cells

Non-fullerene small molecules are more attractive due to their adjustable energy levels, easier synthesis, and low cost of production. Novel non-fullerene acceptor designed materials retain the advantages of fullerene derivatives, as well as overcome the disadvantages of fullerene materials. Modification of novel molecules of end-capped groups was involved to improve the optoelectrical properties of acceptor molecules of OSCs. Herein, the optoelectronic properties of four small new acceptor molecules (PA1-PA4), configured according to the A-D-C-D-A scheme, were studied after the modification of the recently synthesized molecule R (IEICO-4F). The newly designed molecules (PA1-PA4) are comprised of 4,4,9,9-tetra-p-tolyl-4,9-dihydro-s-indaceno[1,2-b:5,6-b']dithiophene (as central core), 3-methoxy thiophene as a donor, which is directly attached with different end-capped acceptors. Some geometric parameters like density of states, binding energy, transition density matrix, absorption maxima, charge transfer analysis and frontier molecular orbitals are performed in order to examine the photovoltaic characteristics of newly designed molecules. Designed molecule (PA1) showed the lowest energy band gap (3.30 eV) with a red-shift in the absorption spectrum (λmax = 870.222 nm) in chloroform which revealed a perfect relationship between end-capped acceptor with large electron-withdrawing character through extended conjugation. PA4 exhibited the highest value of Voc (2.73) among all designed molecules to PTB7-Th donor material. Further, molecular electrostatic potential analysis confirmed the efficient designing of newly designed molecules. Results of all analysis suggested that designed molecules are efficient candidates for high performance organic solar cells.

First principle theoretical designing of W-shaped Dithienosilole-based acceptor materials having efficient photovoltaic properties for high-performance organic solar cells

The key strategy to enhance the intra-molecular push-pull effects by broadening the optial absorption of small molecule based organic photovoltaic (SM-OPV) materials is considered an effective approach to enhance the power conversion efficiencies (PCEs) of SM-OPV devices. However, in case of acceptor materials, the highly desirable molecular modelling strategy of halogenation generally effects in downward-shifting of molecular energy levels, resulting decrease in open-circuit voltages (Voc) in the devices. Herein, we investigate a fluorinated, chlorinated and cyanide (CN) based end-capped acceptor materials, which shows a broader optical absorption phenomenon and exhibited a good voltages than it chlorinated counterparts. These new molecularly engineered SM-OPV were characterize theoretically by density functional theory (DFT) and time-dependent (TD-DFT) approaches. The estimation of electron/hole mobility, and Voc was done by calculating the geometric parameters, electronic structures, frontier molecular orbitals (FMOs), charge transfer rates, and exciton binding energies of the designed OPV materials. The outcomes of these investigations revealed that all newly engineered SM-OPV acceptor materials displays an enhanced exciton dissociation and absorption efficiency and underneath LUMO levels which might be responsible to improve the Voc, reorganization energies, and photo-current density parametrs, resulting enhancement in the PCEs of the organic solar cells (OSC) 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 (683-749nm) of UV-Vis-NIR absorption spectrum with narrowing of HOMO-LUMO energy gap from 2.31eV 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 1.08V in R to 1.20V 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.

In Silico Modeling of New "Y-Series"-Based Near-Infrared Sensitive Non-Fullerene Acceptors for Efficient Organic Solar Cells.

This work was inspired by a previous report [Janjua, M. R. S. A. Inorg. Chem. 2012, 51, 11306–11314] in which the optoelectronic properties were improved with an acceptor bearing heteroaromatic rings. Herein, we have designed four novel Y-series non-fullerene acceptors (NFAs) by end-capped acceptor modifications of a recently synthesized 15% efficient Y21 molecule for better optoelectronic properties and their potential use in solar cell applications. Density functional theory (DFT) along with time-dependent density functional theory (TDDFT) at the B3LYP/6-31G(d,p) level of theory is used to calculate the band gap, exciton binding energy along with transition density matrix (TDM) analysis, reorganizational energy of electrons and holes, and absorption maxima and open-circuit voltage of investigated molecules. In addition, the PM6:YA1 complex is also studied to understand the charge shifting from the donor polymer PM6 to the NFA blend. Results of all parameters suggest that the DA’D electron-deficient core and effective end-capped acceptors in YA1–YA4 molecules form a perfect combination for effective tuning of optoelectronic properties by lowering frontier molecular orbital (FMO) energy levels, reorganization energy, and binding energy and increasing the absorption maximum and open-circuit voltage values in selected molecules (YA1–YA4). The combination of extended conjugation and excellent electron-withdrawing capability of the end-capped acceptor moiety in YA1 makes YA1 an excellent organic solar cell (OSC) candidate owing to promising photovoltaic properties including the lowest energy gap (1.924 eV), smallest electron mobility (λe = 0.0073 eV) and hole mobility (λh = 0.0083 eV), highest λmax values (783.36 nm (in gas) and 715.20 nm (in chloroform) with lowest transition energy values (Ex) of 1.58 and 1.73 eV, respectively), and fine open-circuit voltage (Voc = 1.17 V) with respect to HOMOPM6–LUMOacceptor. Moreover, selected molecules are observed to have better photovoltaic properties than Y21, thus paving the way for experimentalists to look for future developments of Y-series-based highly efficient solar cells.

Designing Star-Shaped Subphthalocyanine-Based Acceptor Materials with Promising Photovoltaic Parameters for Non-fullerene Solar Cells.

Star-shaped three-dimensional (3D) twisted configured acceptors are a type of nonfullerene acceptors (NFAs) which are getting considerable attention of chemists and physicists on account of their promising photovoltaic properties and manifestly promoted the rapid progress of organic solar cells (OSCs). This report describes the peripheral substitution of the recently reported highly efficient 3D star-shaped acceptor compound, STIC, containing a 2-(3-oxo-2,3-dihydroinden-1-ylidene)malononitrile (IC) end-capped group and a subphthalocyanine (SubPc) core unit. The 3D star-shaped SubPc-based NFA compound STIC is peripherally substituted with well-known end-capped groups, and six new molecules (S1–S6) are quantum chemically designed and explored using density functional theory (DFT) and time-dependent DFT (TDDFT). Density of states (DOS) analysis, frontier molecular orbital (FMO) analysis, reorganization energies of electrons and holes, open-circuit voltage, transition density matrix (TDM) surface, photophysical characteristics, and charge-transfer analysis of selected molecules (S1–S6) are evaluated with the synthesized reference STIC. The designed molecules are found in the ambience of 2.52–2.27 eV with a reduction in energy gap of up to 0.19 eV compared to R values. The designed molecules S3–S6 showed a red shift in the absorption spectrum in the visible region and broader shift in the range of 605.21–669.38 nm (gas) and 624.34–698.77 (chloroform) than the R phase values of 596.73 nm (gas) and 616.92 nm (chloroform). The open-circuit voltages are found with the values larger than R values in S3–S6 (1.71–1.90 V) and comparable to R in the S1 and S2 molecules. Among all investigated molecules, S5 due to the combination of extended conjugation and electron-withdrawing capability of end-capped acceptor moiety A5 is proven as the best candidate owing to promising photovoltaic properties including the lowest band gap (2.27 eV), smallest λe = 0.00232 eV and λh = 0.00483 eV, highest λmax values of 669.38 nm (in gas) and 698.77 nm (in chloroform), and highest Voc = 1.90 V with respect to HOMOPTB7-Th–LUMOacceptor. Our results suggest that the selected molecules are fine acceptor materials and can be used as electron and/or hole transport materials with excellent photovoltaic properties for OSCs.

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=0.0044-0.0104eV and λh=0.0060-0.0090eV). Moreover, H1-H5 molecules demonstrate red-shifting in absorption spectrum (λmax=741-812nm) as compare to R (λmax=728nm). 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.

Isatin-derived non-fullerene acceptors for efficient organic solar cells

Geometries optimization, electronic structure, electronic absorption spectra, charge transport rate, morphology, and photovoltaic properties of indacenodithiophene as donor core unit tie with isatin derive different end-capped electron acceptor groups have been performed using Density Functional Theory (DFT) and time dependent density functional theory (TD-DFT). Isatin unit connected with 2-(3-oxo-2,3-dihydro-1H-inden-1-ylidene)malononitrile in M1, 2-(5,6-difluoro-3-oxo-2,3-dihydro-1H-inden-1-ylidene)malononitrile in M2, 2-thioxothiazolidin-4-one in M3, 2-(4-fluorothiophen-2-yl)acetonitrile in M4 and geometries, opto-electronic properties have been computed at TD-DFT MPW1PW91/6-31G level of theory and compared with reference molecule R. Among all novel structures, M2 has lowest value of energy band gap (1.99 eV) and has maximum absorption (λmax = 824.0 nm) in chloroform by TD-MPW1PW91/6-31G (d,p) using IEFPCM model. The red shift in M2 was due presence of strong electron withdrawing acceptor moiety and more extended conjugation as compared to other structures. Indeed, electron withdrawing functionality i.e fluorine and cyno moieties in M2 structure stabilized its LUMO orbital and hence improved its opto-electronic properties. Transition density matrix (TDM) maps results revealed obvious influence of end-capped acceptor group on the exciton. M2 has lower probability of coupling of electron and hole owing easy exciton dissociation as compared to other designed molecules. Theoretically calculated reorganization energy indicates that M1 has the highest hole transfer rate due to the lowest value of λh (0.0068 eV). Similarly, M4 has the highest electron mobility due to lowest value of λe (0.0053 eV). In short, choice of appropriate electron withdrawing end capped acceptor groups is very important for improving the performance of organic solar cells.

Molecular engineering of A–D–C–D–A configured small molecular acceptors (SMAs) with promising photovoltaic properties for high-efficiency fullerene-free organic solar cells

Non fullerene small acceptor molecules in organic photovoltaics are proven beneficial than the traditional fullerene based acceptors for their fine contribution in organic solar cells. Researchers are constantly doing efforts for designing novel acceptor materials with promising photovoltaic properties. Designing of novel molecules by end-capped modifications is a convenient strategy to obtain high efficiency acceptor molecules for OSCs. Herein, we studied optoelectronic characteristics of five novel acceptor–donor–core–donor–acceptor configured small acceptor molecules (S1–S5) after end-capped modifications of recently synthesized DF-PCIC molecule. Designed molecules S1–S5 consist of 1,4-difluorobenzene (as central core), 4,4-bis(2-ethylhexyl)-2,6-dimethyl-4H-cyclopenta[1,2-b:5,4-b′]dithiophene as donor which directly attached with different end-capped acceptors. The electronic and optical properties of newly designed (S1–S5) molecules are examined and compared with reference molecule with the aid of DFT and TD-DFT. Certain key parameters like frontier molecular orbitals analysis, density of states, dipole moment, binding energy along with transition density matrix, excitation energy, charge mobility, absorption maxima and charge transfer analysis have been performed in order to explore the photo-physical, optoelectronic and photovoltaic properties of designed and reference molecule. Out of newly designed structures, S4 displayed lowest energy band-gap (2.25 eV) with red-shifting in absorption spectrum (λmax = 712.43 nm) in chloroform which disclosed the perfect relationship between end-capped acceptor with large electron withdrawing character through extended conjugation. Similarly, S1 exhibited highest value (1.53 V) of open circuit voltage (Voc) with respect to PTB7-Th donor material owing to lower values of λe. Designed molecules exhibit better electron and hole mobility as compared to reference molecule R. All molecules express better absorption maximum, open circuit voltage, low excitation energies, comparable binding energies, large dipole moment and efficient electron and hole transport as compared to reference molecules. So, results these parameters suggest that end-capped modification is a convenient strategy in order to enhance the efficiency of OSCs. Therefore, conceptualized molecules are recommended to experimentalist for out-looking future developments of highly efficient solar cells.