Evaluation of photovoltaic properties and effective conjugated length of DTTTD-based polymers as donor in BHJ solar cells; quantum chemical approach (original) (raw)
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2012
Conjugated polymers with donor−acceptor architectures have been successfully applied in bulk heterojunction solar cell devices. Tuning the electron-withdrawing capability in donor−acceptor (D−A) conjugated polymers allows for design of new polymers with enhanced electrical and optical properties. In this paper, a series of D−A copolymers, PBDFDTBT (P1a), PBDTDTBT (P2a), PNDTDTBT (P3a), and PQDTDTBT (P4a), were selected and theoretically investigated using PBE0/6-311G** and TD-PBE0/6-311G**//PBE0/6-311G** methods. The calculated results agree well with the available experimental data of HOMO energy levels and band gaps. We further designed and studied four novel copolymers, P1b, P2b, P3b, and P4b, by substituting the 2,1,3-benzothiadiazole (BT) unit in P1a−P4a with a stronger unit of naphtho[1,2-c:5,6-c]bis[1,2,5]thiadiazole (NT), respectively. Compared with P1a−P4a, the newly designed polymers of P1b−P4b show better performance with the smaller band gaps and lower HOMO energy levels. The PCEs of ∼5%, ∼7%, ∼7%, and ∼7% for P1b−P4b, predicted by Scharber diagrams, are much higher than those of P1a−P4a when used in combination with PCBM. These results clearly reveal that tuning the electron-withdrawing capability in D−A conjugated polymers is an effective way to improve the electrical and optical properties and the efficiency of the photovoltaic device.
Oxford Open Materials Science
The Density Functional Theory (DFT) and time-dependent-DFT method with Becke’s three-parameter Lee-Yang–Parr functional approach at a basis set of 6-311G was used to analyze the ground state and excited state properties of newly designed donor–acceptor–donor (D–A–D′) donor molecules based on triphenylamine and carbazole as donor units and benzothiadiazole and its derivatives as acceptor units to make a total of nine potential monomers. The energies associated with highest occupied molecular orbital, lowest occupied molecular orbital, energy gap (Eg), electron excitation (Eopt), exciton binding (Eb) and open-circuit voltage (Voc) were calculated, and the simulated absorption spectra in both gas and chlorobenzene solvent were plotted. The outcomes of replacing the acceptor building unit and substituting the donor units to tailor the optoelectronic properties of the designed monomers were discussed. The monomer molecules A7, A8 and A9 are suitable for [6,6]-phenyl-C61-butyric acid meth...
Polym. Chem., 2015
Donor-acceptor conjugated polymers with 2-(2-ethylhexyl)-3-hexyl thienyl substituted benzo [1,2-b:4,5b']dithiophene (BDT) as donor building block and 5,6-difluorobenzo[c][1,2,5]thiadiazole as acceptor building block have been synthesized by Stille coupling polymerization. The polymerization conditions were optimized to achieve high molecular weight polymers (number-average molecular weight, M n , up to 139 kg mol −1 ). The molecular weight dependent polymer properties were studied and compared. Photovoltaic applications of the polymers in bulk heterojunction (BHJ) solar cells revealed that the power conversion efficiency increased significantly (from 0.9% to 4.1%) as the M n increased from 10 kg mol −1 to 73 kg mol −1 while further increase of the molecular weight had less influence on the solar cell performance. † Electronic supplementary information (ESI) available. See
Theoretical and experimental study of low band gap polymers for organic solar cells
Physical Chemistry Chemical Physics, 2012
A combined theoretical and experimental investigation of the electronic structure and optical properties of poly(3-hexylthiophene) (P3HT), poly[3-(4-octylphenyl)thiophene] (POPT) and poly[3-(4-octylphenoxy)thiophene] (POPOT) is reported. In comparison with P3HT, POPT and POPOT exhibit better stabilities and the presence of an oxygen atom and/or a phenyl ring in the side chains enhances conjugation. Quantum chemical calculations have been performed on oligomers of increasing chain length to establish the changes in the electronic and optical properties when going from P3HT to the new derivative POPOT. The knowledge of the structure of these polymers is of utmost importance in understanding their optical properties in different phases (solution and condensed phase). The calculations indicate that, in opposition to P3HT and POPT polymers where the introduction of alkyl chains and the pendant phenyl disturbs the planarity of the backbone of the conjugated segment, POPOT has a better degree of organization in both states: the conjugated chain remains planar even in the presence of the phenoxy groups. Finally, the exciton binding energy is evaluated for these polymers and allows us to conclude that the POPOT is a promising polymer for photovoltaic applications when compared to P3HT and POPT.
THEORETICAL STUDY OF NEW CANDIDATE ORGANIC MATERIALS FOR PHOTOVOLTAIC APPLICATIONS
Granthaalayah Publications and Printers, 2023
Our work consists of a theoretical prediction, through DFT and TD-DFT methods, of the electronic and optical properties of six conjugated organic compounds used as electron donor materials in BHJ solar cells, of which PCBM is the acceptor material. This study is necessary to discuss the effect of substituents (donor units) on the different properties of these compounds, and to predict promising materials in organic solar cells using the AMPS-1D simulation software. The results obtained show that all the molecules have good geometric, electronic, and optical properties, thus showing an increase in the power conversion efficiency of photovoltaic cells based on these materials, which reaches a value of 17% for the molecule P-Eth-TEdotT-A.
Journal of Photochemistry and Photobiology A: Chemistry, 2013
After the discovery of photoinduced charge transfer in conjugated polymers, organic photovoltaic solar cells have been extensively studied due to many advantages that include flexibility and low-cost. In this context, we have synthesized a new class of conjugated polymer, poly(2-(4-{1-cyano-2-[5-(3-thiophen-2-yl-benzo[c]thiophen-1-yl)-thiophen-2-yl]-vinyl}-2,5bis-hexyloxy-phenyl)-but-2-enenitrile) (CN-PTBTBPB) for the fabrication of low cost organic solar cells. The electron donor properties of CN-PTBTBPB polymer was incorporated by means of facile Knoevenagel condensation process followed by a chemical oxidative polymerization method using oligo-5-(1-benzo[c]thiophen-3-yl)thiophene-2-carboxaldehyde with 1,4-bis(cyanomethyl) benzene linkages. The polymer was characterized by 1 H NMR and GPC techniques. The electronic and structural properties of the polymer were evaluated by UV-vis spectroscopy, fluorescence spectroscopy, and thermo gravimetric analysis. In order to establish the energy diagram of the prepared polymer, the energy gap between HOMO-LUMO was evaluated using electrochemical measurements and Density Functional Theory (DFT). The resulting CN-PTBTBPB polymer was experimentally found to possess low-lying HOMO (about −5.84 eV) and high-lying LUMO (about −3.87 eV) energy levels. This polymer exhibited a relatively wide optical band gap of ∼1.95 eV in the solid state. Using this polymer, organic photovoltaic cells were fabricated in open air of type ITO/PEDOT:PSS/CN-PTBTBPB:PCBM/Al showed promising photovoltaic properties.
Journal of Photonics for Energy, 2015
Conjugated polymers are potential materials for photovoltaic applications due to their high absorption coefficient, mechanical flexibility, and solution-based processing for low-cost solar cells. A bulk heterojunction (BHJ) structure made of donor-acceptor composite can lead to high charge transfer and power conversion efficiency. Active layer morphology is a key factor for device performance. Film formation processes (e.g., spray-coating, spin-coating, and dip-coating), post-treatment (e.g., annealing and UV ozone treatment), and use of additives are typically used to engineer the morphology, which optimizes physical properties, such as molecular configuration, miscibility, lateral and vertical phase separation. We will review electronic donoracceptor interactions in conjugated polymer composites, the effect of processing parameters and morphology on solar cell performance, and charge carrier transport in polymer solar cells. This review provides the basis for selection of different processing conditions for optimized nanomorphology of active layers and reduced bimolecular recombination to enhance open-circuit voltage, short-circuit current density, and fill factor of BHJ solar cells.
Recent Developments in Organic Polymers Based- Photovoltaic Cells
ABSTRACT: In this review article, the uses of organic polymers to make photovoltaic cells have been discussed. The focus is mainly on discussing organic polymer based photovoltaic (OPVs) solar cells, the development of new device technologies and donor polymers that are being researched on. The recent development in this field has led to improved OPV performances with power conversion efficiencies as phenomenal as 9%. However for commercial application of this kind of OPVs, an improved device structure and cost effective processing methods are required. This article reports the polymer design criteria, energy level matching, nano-morphing of polymer/acceptor blend films and local dipole moments of the polymer chains that have been developed in the research that took place over the past 4 years. We emphasize the importance of developing new methods for designing polymers with improved physical properties and development of new technologies to fully understand the fundamentals of OPV mechanisms, which will help improve the power conversion efficiency of the OPV.