Alternating Donor Acceptor Research Articles

Transforming Thermally Activated Delayed Fluorescence to Room-Temperature Phosphorescence through Modulation of the Donor in Charge-Transfer Cocrystals.

A cocrystallization strategy is used through incorporation of 1,2,4,5-tetracyanobenzene (TCNB) as an acceptor with halogen-substituent thioxanthone (TX) derivatives as donors. The resulting cocrystals TT-R (R = H, F, Cl, Br, or I) transform the thermally activated delayed fluorescence emission in the TT-H, TT-F, and TT-Cl cocrystals to room-temperature phosphorescence in the TT-Br and TT-I cocrystals. Definite crystal packing structures demonstrate a 1:1 alternative donor-acceptor stacking in the TT-H cocrystal, a 2:1 alternative donor-acceptor stacking in the TT-F and TT-Cl cocrystals, and a separate stacking of donor and acceptor in the TT-Br and TT-I cocrystals. A transformation law can be revealed that with an increase in atomic number from H, F, Cl, Br, to I, the cocrystals show the structural transformation of the number of aggregated TX-R molecules from monomers to dimers and finally to multimers. This work will facilitate an understanding of the effect of halogen substituents on the crystal packing structure and luminescence properties in the cocrystals.

Preparation and Physicochemical Properties of Organic Semiconducting Materials from the Reaction of Imidazo[1,2‐a]pyridines with Tetracyanoethylene

AbstractOrganic donor‐acceptor (DA) complexes have emerged in recent years as materials of choice for organic binary electronics. The reactivity descriptors derived from the conceptual DFT reveal imidazo[1,2‐a]pyridines as potential donors. Thus, four imidazo[1,2‐a]pyridines were reacted with tetracyanoethylene (TCNE) in 1 : 2 molar ratio to afford four new DA complexes. The spectral studies, namely IR, 1H, 13C, DEPT 135, 2D HMQC NMR, and HRMS were used to establish structures of the products. The UV‐vis. spectroscopy reveals intramolecular charge transfer. All the four compounds fluoresce giving excitation emission fluorescence spectra with a red shift ranging from 64 to 151 nm and quantum yields from 0.004 to 16.35. Unexpectedly, nitro group in one of the products does not act as quencher; instead, it enhances the quantum yield to make it highest in this series. The products exhibit electrical conductivity which increases with temperature. The FESEM and HRTEM images reveal distinct and homogenous surface morphology with holes which facilitate flow of electrons as manifested by electrical conductivity. The powder XRD and SAED results establish the polycrystalline nature of the products. The theoretical studies indicate an alternate donor acceptor stacking pattern.

Through-Space Charge-Transfer Thermally Activated Delayed Fluorescence Alternating Donor–Acceptor Copolymers for Nondoped Solution-Processable OLEDs

Through-Space Charge-Transfer Thermally Activated Delayed Fluorescence Alternating Donor–Acceptor Copolymers for Nondoped Solution-Processable OLEDs

A Mini Review on the Development of Conjugated Polymers: Steps towards the Commercialization of Organic Solar Cells

This review article covers the synthesis and design of conjugated polymers for carefully adjusting energy levels and energy band gap (EBG) to achieve the desired photovoltaic performance. The formation of bonds and the delocalization of electrons over conjugated chains are both explained by the molecular orbital theory (MOT). The intrinsic characteristics that classify conjugated polymers as semiconducting materials come from the EBG of organic molecules. A quinoid mesomeric structure (D-A ↔ D+ = A-) forms across the major backbones of the polymer as a result of alternating donor-acceptor segments contributing to the pull-push driving force between neighboring units, resulting in a smaller optical EBG. Furthermore, one of the most crucial factors in achieving excellent performance of the polymer is improving the morphology of the active layer. In order to improve exciton diffusion, dissociation, and charge transport, the nanoscale morphology ensures nanometer phase separation between donor and acceptor components in the active layer. It was demonstrated that because of the exciton's short lifetime, only small diffusion distances (10-20 nm) are needed for all photo-generated excitons to reach the interfacial region where they can separate into free charge carriers. There is a comprehensive explanation of the architecture of organic solar cells using single layer, bilayer, and bulk heterojunction (BHJ) devices. The short circuit current density (Jsc), open circuit voltage (Voc), and fill factor (FF) all have a significant impact on the performance of organic solar cells (OSCs). Since the BHJ concept was first proposed, significant advancement and quick configuration development of these devices have been accomplished. Due to their ability to combine great optical and electronic properties with strong thermal and chemical stability, conjugated polymers are unique semiconducting materials that are used in a wide range of applications. According to the fundamental operating theories of OSCs, unlike inorganic semiconductors such as silicon solar cells, organic photovoltaic devices are unable to produce free carrier charges (holes and electrons). To overcome the Coulombic attraction and separate the excitons into free charges in the interfacial region, organic semiconductors require an additional thermodynamic driving force. From the molecular engineering of conjugated polymers, it was discovered that the most crucial obstacles to achieving the most desirable properties are the design and synthesis of conjugated polymers toward optimal p-type materials. Along with plastic solar cells (PSCs), these materials have extended to a number of different applications such as light-emitting diodes (LEDs) and field-effect transistors (FETs). Additionally, the topics of fluorene and carbazole as donor units in conjugated polymers are covered. The Stille, Suzuki, and Sonogashira coupling reactions widely used to synthesize alternating D-A copolymers are also presented. Moreover, conjugated polymers based on anthracene that can be used in solar cells are covered.

Moving Beyond Cyanoarene Thermally Activated Delayed Fluorescence Compounds as Photocatalysts: An Assessment of the Performance of a Pyrimidyl Sulfone Photocatalyst in Comparison to 4CzIPN.

Carbazolyl dicyanobenzene (CDCB) derivates exhibiting thermally activated delayed fluorescence (TADF) have shown themselves to be excellent photocatalysts over recent years, particularly 4CzIPN, although investigation into organic TADF compounds as photocatalysts outside of the CDCB group has been limited. Herein, we report an alternative donor-acceptor TADF structure, 9,9'-(sulfonylbis(pyrimidine-5,2-diyl))bis(3,6-di-tert-butyl-9H-carbazole), pDTCz-DPmS, for use as a photocatalyst (PC). A comparison of the electrochemical and photophysical properties of pDTCz-DPmS with 4CzIPN in a range of solvents identifies the former as a better ground state reducing agent and photoreductant, while both exhibit similar oxidation capabilities in the ground and excited state. The increased conjugation of pDTCz-DPmS relative to 4CzIPN presents a more intense CT band in the UV-vis absorption spectrum, aiding in the light absorption of this molecule. Prompt and delayed emission lifetimes are observed for pDTCz-DPmS, confirming the TADF nature, both of which are sufficiently long-lived to participate in productive photochemistry. These combined properties make pDTCz-DPmS useful in photocatalysis reactions, covering a range of photoredox oxidative and reductive quenching reactions, as well as those involving a dual Ni(II) cocatalyst, alongside energy transfer processes. The higher triplet energy and increased photostability of pDTCz-DPmS compared with 4CzIPN were found to be advantages of this organic PC.

Synthetic Route to Conjugated Donor-Acceptor Polymer Brushes via Alternating Copolymerization of Bifunctional Monomers.

Alternating donor–acceptor conjugated polymers, widely investigated due to their applications in organic photovoltaics, are obtained mainly by cross-coupling reactions. Such a synthetic route exhibits limited efficiency and requires using, for example, toxic palladium catalysts. Furthermore, the coating process demands solubility of the macromolecules, provided by the introduction of alkyl side chains, which have an impact on the properties of the final material. Here, we present the synthetic route to ladder-like donor–acceptor polymer brushes using alternating copolymerization of modified styrene and maleic anhydride monomers, ensuring proper arrangement of the pendant donor and acceptor groups along the polymer chains grafted from a surface. As a proof of concept, macromolecules with pendant thiophene and benzothiadiazole groups were grafted by means of RAFT and metal-free ATRP polymerizations. Densely packed brushes with a thickness up to 200 nm were obtained in a single polymerization process, without the necessity of using metal-based catalysts or bulky substituents of the monomers. Oxidative polymerization using FeCl3 was then applied to form the conjugated chains in a double-stranded (ladder-like) architecture.

Design, Synthesis, and Application in OFET of a Quinoxaline-Based D-A Conjugated Polymer.

A novel alternating donor–acceptor polymer PQ1 is designed and synthesized by palladium-catalyzed Stille coupling between quinoxaline as an electron-deficient unit and indacenodithiophene (IDT) as electron-rich groups. Polymer PQ1 presents not only a strong intramolecular charge transfer effect, which is beneficial for the charge transport within single molecules but also a narrow electrochemical band gap and a high highest occupied molecular orbital (HOMO) energy level. In addition, the optical absorption study indicates that the PQ1 film exhibits good aggregation, which is an advantage for the charge transport between neighboring molecules. As a consequence, PQ1 presents p-type semiconductor properties with a high hole mobility of up to 0.12 cm2 V−1 s−1. This study reveals the great potential of quinoxaline-type chromophores in constructing novel organic semiconductors.

A Thiazole-Based Polymer Donor for Efficient Organic Solar Cells

The development of new materials plays a critical role in improving the efficiency of organic solar cells (OSCs). At present, the relatively high-lying highest occupied molecular orbital (HOMO) level of the high-efficiency polymer donor is regarded as one of the main reasons for the low open-circuit voltage (Voc). In this work, we introduced the strong electron-withdrawing thiazole unit into the construction of a polymer donor. We designed and prepared an alternating donor–acceptor material, namely PSZ, by copolymerizing 4-methyl thiazole with an electron-donating benzodithiophene unit and studied its application in high-efficiency OSCs. The optical and electrical properties of the new material were characterized by UV–Vis absorption spectroscopy and electrochemical cyclic voltammetry. Results show that PSZ is a typical wide-bandgap material with a high optical bandgap of 2.0 eV and a deep HOMO level of − 5.70 eV. When a non-fullerene BTP-eC9 was selected as the acceptor material, Voc reached 0.88 V in the resulting device, and the corresponding power conversion efficiency (PCE) was 8.15%. In addition, when PSZ was added as the third component to the binary photoactive combination with PBDB-TF as the donor and BTP-eC9 as the acceptor, Voc of the cell device could be increased, thereby obtaining a high PCE of 17.4%. These results indicated that introducing thiazole units into polymer donors can remarkably reduce the HOMO levels and improve Voc and PCE in OSCs.

Chirality-Controlled Supramolecular Donor-Acceptor Copolymerization with Distinct Energy Transfer Efficiency.

Chirality delivers substantial value to the field of supramolecular polymers, not only serving as a probe to monitor the dynamic assembly process but providing access to chiroptical materials. The current study demonstrates that, for supramolecular donor-acceptor copolymers, their comonomer organization modes can be greatly influenced by stereocommunication at the molecular level. The enantiopure N-[(1R or 1S)-phenylethyl]benzamides are incorporated into two structurally similar comonomers, locating between the π-aromatic diethynylacene core and the alkyl chain peripheries. Parallel arrangement of the stereogenic methyl units brings steric hindrance between the homochiral comonomers, which is relieved for the heterochiral comonomers due to the adoption of staggered arrangement. It consequently steers randomly mixed organization for the homochiral supramolecular copolymers within the nanofibers. In comparison, the heterochiral counterparts form nanoparticles in an alternate donor-acceptor organization manner. The variation of comonomer arrangement modes gives rise to distinct energy transfer efficiency at the supramolecular level. Overall, the elaborate manipulation of stereogenic centers in the comonomer structures exerts significant impacts on the characteristics of supramolecular copolymers, which could be useful for chiral sensing, recognition, and optoelectronic applications.

Alternating Donor–Acceptor π‐Conjugated Macrocycle Exhibiting Efficient Thermally Activated Delayed Fluorescence and Spontaneous Horizontal Molecular Orientation

A versatile design of thermally activated delayed fluorescence (TADF) π‐conjugated macrocycles incorporating electron‐donor (D) and acceptor (A) units into a cyclo‐meta‐phenylene motif with an alternating pattern is presented. The new π‐conjugated macrocycle, which combines three 5‐(N‐carbazolyl)‐phenylen‐1,3‐diyl as D units and three 6‐phenyl‐1,3,5‐triazin‐2,4‐diyl as A units, possesses a small singlet–triplet energy gap and hence can emit efficient green TADF both in solution and doped thin films. Comparative experimental and computational investigations of the electronic and photophysical properties of the macrocycle with its analogous noncyclic compound reveal key advantages of the cyclic molecular configuration for actual emitters. Organic light‐emitting diodes incorporating the TADF π‐conjugated macrocycle as an emitter demonstrate high external electroluminescence quantum efficiencies of up to 15.7%, outperforming the devices based on the noncyclic emitter. Herein, the importance of geometric design for producing novel organic emitters with fascinating optoelectronic and morphological characteristics is highlighted.

Revealing Donor Substrate-Dependent Mechanistic Control on DXPS, an Enzyme in Bacterial Central Metabolism.

The thiamin diphosphate-dependent enzyme 1-deoxy-d-xylulose 5-phosphate synthase (DXPS) catalyzes the formation of DXP from pyruvate (donor) and d-glyceraldehyde 3-phosphate (d-GAP, acceptor). DXPS is essential in bacteria but absent in human metabolism, highlighting it as a potential antibacterial drug target. The enzyme possesses unique structural and mechanistic features that enable development of selective inhibition strategies and raise interesting questions about DXPS function in bacterial pathogens. DXPS distinguishes itself within the ThDP enzyme class by its exceptionally large active site and random sequential mechanism in DXP formation. In addition, DXPS displays catalytic promiscuity and relaxed acceptor substrate specificity, yet previous studies have suggested a preference for pyruvate as the donor substrate when d-GAP is the acceptor substrate. However, such donor specificity studies are potentially hindered by a lack of knowledge about specific, alternative donor–acceptor pairs. In this study, we exploited the promiscuous oxygenase activity of DXPS to uncover alternative donor substrates for DXPS. Characterization of glycolaldehyde, hydroxypyruvate, and ketobutyrate as donor substrates revealed differences in stabilization of enzyme-bound intermediates and acceptor substrate usage, illustrating the influence of the donor substrate on reaction mechanism and acceptor specificity. In addition, we found that DXPS prevents abortive acetyl-ThDP formation from a DHEThDP carbanion/enamine intermediate, similar to transketolase, supporting the potential physiological relevance of this intermediate on DXPS. Taken together, these results offer clues toward alternative roles for DXPS in bacterial pathogen metabolism.

Donor–Acceptor Polymers Containing 4,8-Dithienylbenzo[1,2-b:4,5-b′]dithiophene via Highly Selective Direct Arylation Polymerization

While palladium-catalyzed direct arylation polymerization (DArP) is an easy and safe method to synthesize semiconducting polymers with alternating donor–acceptor units (DA polymers), branching and cross-linking defects arising from unintended side reactions are common. When these polymers are used as electronic materials in organic solar cells (OSCs) and similar devices, these defects may adversely affect device performance. We have recently shown that the side reactions can be inhibited by the simultaneous presence of two ligands, P(2-MeOC6H4)3 and N,N,N′,N′-tetramethylethylenediamine (TMEDA). In this study, an efficient donor polymer for OSCs (P1), based on 4,8-dithienylbenzo[1,2-b:4,5-b′]dithiophene (DTBDT) units, was prepared with this mixed-ligand method. The DA polymer is found to exhibit a well-controlled structure, with homocoupling defects of 2.0%, compared to 14.8% observed in the Migita–Stille product (P2). The power conversion efficiency (PCE) was 9.9% when P1 was used, compared to 9.8% for P2 in bulk-heterojunction-type OSC with a nonfullerene acceptor. This demonstrates the effectiveness of the DArP method as a clean and safe alternative method to synthesize DTBDT-based DA polymers for OSCs.

Synthesis and third-order nonlinear optical properties of low band gap 3,4-ethylenedioxythiophene-thiophene copolymers

Alternate donor–acceptor 3,4-ethylenedioxythiophene (EDOT) based copolymers with thiophene and 3-methyl thiophene were designed by employing density functional theory (DFT) in the periodic boundary condition using HSE06 exchange correlation functional and 6-31G basis set. The designed copolymers were synthesized via a simple and facile route, i.e., direct arylation and their third-order nonlinear optical properties were investigated by Z-scan technique. The resultant copolymers, P(EDOT-THP) and P(EDOT-MeTHP) were characterized by spectroscopic analysis. The photophysical and electrochemical properties of EDOT-thiophene copolymers were investigated by UV–visible spectra and cyclic voltammetry, respectively. The copolymers revealed low band gap and better electronic properties as compared to the homopolymers. The introduction of EDOT unit in the polythiophene leads to decreased HOMO-LUMO energy levels, and the absorption spectra was red shifted when compared with that of the parent compound. The nonlinear absorption and nonlinear refraction coefficient of copolymers have been investigated at 532 nm. The optical limiting properties of copolymers have also been measured. The copolymers exhibited strong optical nonlinearity owing to the presence of alternate donor-π-acceptor scheme in the polymers.

Rational design of novel isoindigo based donor–acceptor type conjugated polymers with low bandgaps as solution-processed high-performance electrochromic materials

Isoindigo, an electron deficient heteroaromatic compound, was developed as a great potential building block in the construction of low bandgap conjugated polymers with enhanced optoelectronic performances. Herein, via the Donor–Acceptor approach, a novel range of conjugated copolymers were rationally designed and synthesized by employing isoindigo as acceptor, electron rich fused thiophenes (i.e. thieno[3,2-b]thiophene, cyclopentadithiophene) as donors. The polymeric films can be easily obtained via spray-coating method due to their excellent solubility in common solvent. The optoelectronic properties of these copolymers were detailedly studied by electrochemical and spectroelectrochemical methods. Owing to the alternating donor–acceptor structure in the polymer backbones, as-prepared copolymers showed outstanding reversible redox activity and stability as well as tunable spectroscopic properties (e.g. bandgaps, colors) depending on the composition (i.e. D–A ratio) of the copolymers. These polymeric films demonstrated low bandgaps (Eg) ranging from 1.50 to 1.53 eV. Importantly, the as-prepared films revealed distinct electrochromic switching behaviors. Highly enhanced electrochromic performance, such as high optical contrast (56.9–80.8%), fast response time (0.36–0.94 s) and high coloring efficiency (300–466.67 cm2 C−1) were found for the polymeric films in the visible or near-IR region due to the rationally designed D–A structure. Furthermore, these polymeric films showed remarkable thermal stability. All the above features make this kind of D–A typed copolymers a promising candidate for the electrochromic application.

Structure and Doping Optimization of IDT-Based Copolymers for Thermoelectrics.

π-conjugated backbones play a fundamental role in determining the thermoelectric (TE) properties of organic semiconductors. Understanding the relationship between the structure–property–function can help us screen valuable materials. In this study, we designed and synthesized a series of conjugated copolymers (P1, P2, and P3) based on an indacenodithiophene (IDT) building block. A copolymer (P3) with an alternating donor–acceptor (D-A) structure exhibits a narrower band gap and higher carrier mobility, which may be due to the D-A structure that helps reduce the charge carrier transport obstacles. In the end, its power factor reaches 4.91 μW m−1 K−2 at room temperature after doping, which is superior to those of non-D-A IDT-based copolymers (P1 and P2). These results indicate that moderate adjustment of the polymer backbone is an effective way to improve the TE properties of copolymers.

Optoelectronic properties of cyclopentadithiophene-based donor–acceptor copolymers as donors in bulk heterojunction organic solar cells: A theoretical study

Cyclopentadithiophene and benzothiadiazole derivatives have promising characteristics for use in organic solar cells. In this study, we theoretically investigated two donor–acceptor copolymers comprising 2-(benzo[c][1,2,5]thiadiazol-4-yl)-4H-cyclopenta[2,1-b:3,4-b']dithiophen-4-one and 2-(2-(benzo[c][1,2,5]thiadiazol-4-yl)-4H-cyclopenta[2,1-b:3,4-b']dithiophen-4-ylidene)malononitrile with alternating donor–acceptor building units. Different copolymer chain lengths (n = 1–5) were extended to investigate their structural, electronic, and photo-physical properties based on density functional theory calculations. The copolymers exhibited high planarity, reduced band gap energies, and broad absorption in the visible range, and thus they may enhance the performance of organic solar cells. The transition density matrix plots were simulated for the copolymers and used to evaluate hole–electron localization interactions, donor–acceptor interactions, and the electronic excitation processes in their excited states. The charge transfer properties, fill factors, and open-circuit voltages were estimated. Based on our simulations, we found that the trimer was the most suitable conformation among the copolymers for designing high performance bulk heterojunction (BHJ) solar cells. The power conversion efficiency of the BHJ-based blended copolymers-[70]PCBM was estimated as 9.5%. Thus, the appropriate design of conjugated materials could considerably enhance the donor properties to further improve the performance of BHJ solar cells.

Efficient Blue Phosphorescent OLEDs with Improved Stability and Color Purity through Judicious Triplet Exciton Management

AbstractHighly efficient and stable blue phosphorescent organic light‐emitting diodes are achieved by employing a step‐wise graded doping of platinum(II) 9‐(pyridin‐2‐yl)‐2‐(9‐(pyridin‐2‐yl)‐9H‐carbazol‐2‐yloxy)‐9H‐carbazole (PtNON) in a device setting. A device employing PtNON demonstrates a high peak external quantum efficiency (EQE) of 17.4% with an estimated LT70 lifetime of over 1330 h at a brightness of 1000 cd m−2. PtNON is then investigated as a “triplet sensitizer” in an alternating donor–acceptor doped emissive layer to further improve the device emission color purity by carefully managing an efficient Förster resonant energy transfer from PtNON to 2,5,8,11‐tetra‐tert‐butylperylene as a selected acceptor material. Thus, such OLED devices demonstrate an EQE of 16.9% with color coordinates of (0.16, 0.25) and an estimated luminance (LT70) lifetime of 628 h at a high brightness of 1000 cd m−2.

Directed Assembly of Hierarchical Supramolecular Block Copolymers: A Strategy To Create Donor–Acceptor Charge-Transfer Stacks

The hierarchical self-assembly of the charge-transfer (CT) complexes in the solid state is of paramount importance to dictate the performance of electronic devices. In this work, we describe a three-component hierarchical self-assembly approach to generate stable alternate donor–acceptor (D–A) assemblies within block copolymer microdomains by involving the supramolecular approach in self-assembly of block copolymers. So far, the assembly between a single small molecule and block copolymer was explored to obtain block copolymer supramolecules. Here we report block copolymer supramolecules composed of two small molecules (donor and acceptor) and polystyrene-block-poly(4-vinylpyridine) (PS-b-P4VP). 1-Pyrenebutyric acid (PBA, donor) forms hydrogen bonding with P4VP and aromatic interactions with naphthalene diimide (NDI, acceptor) to generate CT complexes within the block copolymer domains in the solid state. Using FTIR, SAXS, WAXS, TEM, UV/vis spectroscopy, and photoluminescence spectroscopy measurements, we demonstrate the formation of hierarchical structures and CT complexes between PBA and NDI. Space charge limited current analysis showed the enhanced charge carrier mobility in PS-b-P4VP (PBA+NDI) supramolecules compared to that in the physical blends of PBA+NDI. The organization of donor and acceptor molecules within the block copolymer microdomains opens up new insight into the area of electronic devices because of its advantages such as solution processability, controlled formation of hierarchical assemblies, and the CT interaction in the solid state.

Designing Donor-Acceptor thienopyrazine derivatives for more efficient organic photovoltaic solar cell: A DFT study

The present work focuses on the design and development of new thienopyrazine-derivatives in alternate Donor-Acceptor (D-A) structure for solar cells applications. Eight molecules based on thienopyrazine combined with the electron-rich thiophene or bithiophene units have been investigated using the DFT and TDDFT methods with B3LYP functional implemented with 6-31G(d,p) basis set. The focus was on the effect of substitution and doping on the structural, optoelectronic, photovoltaic and transporting properties. The result shows that the substitution by bithiophene groups decreases energy gap (Eg), produces a high bathochromic shift and increases oscillator strength of the lowest-lying transition compared to the substitution with thiophene groups. The doping of studied molecules makes them more planar and improves their electronic properties. Other characteristics, such as the ionization potential (IP), electronic affinity (EA), reorganization energies (λ+ and λ−), voltage in open circuit (Voc), and charge transfer are discussed. All of the molecules show moderate values of voltage in open circuit and efficient charge transfer. In the light of these results, we suggest promising models of systems for applications in optoelectronic. OPVC solar cell based on the most appropriate designed molecule (low band gap and high VOC) in bulk heterojunction composite with [6,6] -phenyl-C61-butyric acid methyl ester (PCBM) as an acceptor has been modeled. A model energy band diagram is described for OPVC to simulate the energy transfer between active layers. These materials are potentially interesting for the realization of optoelectronic devices and can be qualified as future materials for renewable energy.

New organic materiel based on benzothiadiazole for Photovoltaic application Solar Cells

Abstract In this work, we have studied conjugated polymers based on benzothiadiazole. the quantum chemical calculations on the structure and electronic and optics properties using the density functional theory (DFT), for the ground- and excited-state properties, respectively, using CAM-B3LYP and the 6-31G(d, p) basis set. These results will be devoted to the influence of the substitution benzothiadiazole on the electronic and optoelectronic properties of the polymer. The highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) levels of these compounds were calculated and compared to LUMO of fullerenes,C60 [6,6]-phenyl- C61-butyric-acid methyl ester to estimate the effectiveness of these molecules as electron donors in bulk heterojunction (BHJ) small molecules-fullerene solar cells. The absorption energies have been obtained from TD-DFT calculations performed on the excited-state optimized S geometries. Finally, the theoretical results suggest that both the introduction of benzothiadiazole groups contribute significantly to the electronic and optoelectronic properties of the alternating donor–acceptor–donor conjugated systems studied.