Benzothiadiazole Research Articles

A sensitive amperometric AChE-biosensor for organophosphate pesticides detection based on conjugated polymer and Ag-rGO-NH2 nanocomposite

Long-term accumulation of organophosphate pesticides in environment presents a potential hazard to human and animal health. Towards this, a highly sensitive amperometric AChE-biosensor based on conjugated polymer and Ag-rGO-NH2 nanocomposite has been successfully developed. First, 4, 7-di (furan-2-yl) benzo thiadiazole (FBThF) was electrochemically polymerized on the electrode surface. Then, Ag-rGO-NH2 nanocomposite and acetylcholinesterase (AChE) are modified on the polymer membrane surface. In this way, a novel amperometric AChE-biosensor was successfully prepared. The as-prepared biosensor possessed excellent conductivity, catalytic activity, and biocompatibility which were attributed to the synergistic effects of poly(FBThF) and Ag-rGO-NH2 and provided a hydrophilic surface for AChE adhesion. Under optimized conductions, the linear range was 0.099–9.9 μg L−1 with a regression coefficient of 0.9947 for malathion, 0.0206–2.06 μg L−1 with a regression coefficient of 0.9969 for trichlorfon. The detection limit is calculated to be about 0.032 μg L−1 for malathion and 0.001 μg L−1 for trichlorfon (S/N = 3). Moreover, the biosensor exhibited acceptable reproducibility and long-term stability, which makes it possible to provide a novel and promising tool for analysis of organophosphate pesticides.

Spirobifluorene based small molecules as an alternative to traditional fullerene acceptors for organic solar cells

Four new three-dimensional (3D) acceptor-acceptor-donor (A-A-D) type of small molecule acceptors (M1, M2, M3 and M4) were designed for better optoelectronic properties in organic solar cells. These molecules contain spirobifluorene as a 3D core unit, flanked with 2,1,3- benzothiadiazole (BT) units linked with the end-capped acceptor groups 2-(4-oxo-4,5-dihydrocyclopenta-b-thiophene-6-ylidene)malononitrile (M1), 2-(3-oxo-2,3-dihydro-1H-indene-1-indene-1-ylidene)malononitrile (M2), 2-(5,6-difluoro-3-oxo-2,3-dihydroindene-1-ylidene)malononitrile (M3) and 2-(5,6-dimethyl-3-oxo-2,3-dihydroindene-1-ylidene)malononitrile (M4). The optoelectronic properties of M1-M4 were compared with the well-known reference molecule R, which has the same central BT-spirobifluorene-BT structure as M1-M4 but is end-capped with the 2-(2-dicyanomethylene)-3-ethyl-4-oxo-thiazolidin-5-ylidenemethyl group. Among these molecules, M3 has the most appropriate frontier molecular orbital diagram for optoelectronic properties as deduced from MPW1PW91 calculations and also shows the maximum absorption peak at longest wavelength (569 nm) by TD-MPW1PW91 calculations with a polarizable continuum model for chloroform solution. These properties are due to the strong electron-withdrawing end-capped acceptor group which causes a red shift in the absorption spectrum. Computed reorganization energies indicate that the electron mobilities for M1-M4 are higher compared to that of reference R.

A DFT/TDDFT investigation on the efficiency of novel dyes with ortho-fluorophenyl units (A1) and incorporating benzotriazole/benzothiadiazole/phthalimide units (A2) as organic photosensitizers with D–A2–π–A1 configuration for solar cell applications

Novel derivatives of OD1 with D–A2–π–A1 configuration have been designed. The calculated geometrical parameters and optoelectronic properties are compared with those of the parent triphenylamine-based dye molecule (OD1) comprising a triphenylamine terminal electron-rich group (D), 3,4-ethylene dioxythiophene π-spacer, fluorophenyl electron-withdrawing group (A1), and cyanoacrylic acid anchor group. The designed derivatives differ from OD1 with D–π–A1 configuration in the incorporation of an electron-acceptor group (A2) between the donor group and π-spacer unit, namely benzotriazole (BTZ), benzothiadiazole (BTDZ), or phthalimide (PHI), denoted as ND2-BTZ, ND3-BTDZ, and ND4-PHI, respectively. The effects of the incorporation of each electron-deficient unit on the geometry, absorption spectra, and electrochemical properties are investigated by using density functional theory (DFT) and time-dependent (TD)DFT methods. Additionally, the preferred dye adsorption process on model Ti(OH)4 is investigated. The results for the binding energy, selected bond distances, highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energy levels and their distribution, energy gaps, and total density of states (TDOS) plots are discussed and analyzed. The intermolecular interaction between two monomers of each dye and iodine is also investigated, and the complexation energy [corrected for the basis set superposition error (BSSE)] is calculated and analyzed. The results reveal that the introduction of the BTDZ and PHI functional groups is more promising for formation of organic dyes with D–A2–π–A1 configuration.

Vinyl-functionalized multicolor benzothiadiazoles: design, synthesis, crystal structures and mechanically-responsive performance

Benzothiadiazole (BTD) has been extensively used as a building block in optical materials. In this work, a class of π-conjugated BTD-based luminogens BTD-685 , BTD-580 , BTD-675 and BTD-565 were designed by varying donor units and facilely synthesized by Heck coupling reaction. It was found that their emission in solid state covered the regio from orange, red to near infrared fluorescence. Investigation on photo-physical property manifested that they had strong solvatochromic behavior except symmetric 2-vinylpyridine substituted BTD-565 . Crystal X-ray diffraction analysis revealed that they involved in multi weak intermolecular interactions. And loose molecular packing implied that they can be easily rearranged under external force stimuli. Indeed, all compounds showed reversible mechanically-responsive behavior in solid state. Interestingly, the vinylpyridine-containing BTD-565 exhibited hypochromatic mechanochromic behavior, whereas others showed bathochromic mechanochromism behavior. It was worth mentioning that BTD-675 had self-recovery behavior after grinding. The powder X-ray diffraction study showed that these chromic processes may be mainly attributed to the reversible morphological changes between crystalline and amorphous phase upon grinding or fuming. These observations suggested that the vinyl-functionalized benzothiadiazoles can be considered as a type of excellent candidates in mechanically-responsive chromic materials.

Single-Junction Organic Solar Cell with over 15% Efficiency Using Fused-Ring Acceptor with Electron-Deficient Core

Summary Recently, non-fullerene n-type organic semiconductors have attracted significant attention as acceptors in organic photovoltaics (OPVs) due to their great potential to realize high-power conversion efficiencies. The rational design of the central fused ring unit of these acceptor molecules is crucial to maximize device performance. Here, we report a new class of non-fullerene acceptor, Y6, that employs a ladder-type electron-deficient-core-based central fused ring (dithienothiophen[3.2-b]- pyrrolobenzothiadiazole) with a benzothiadiazole (BT) core to fine-tune its absorption and electron affinity. OPVs made from Y6 in conventional and inverted architectures each exhibited a high efficiency of 15.7%, measured in two separate labs. Inverted device structures were certified at Enli Tech Laboratory demonstrated an efficiency of 14.9%. We further observed that the Y6-based devices maintain a high efficiency of 13.6% with an active layer thickness of 300 nm. The electron-deficient-core-based fused ring reported in this work opens a new door in the molecular design of high-performance acceptors for OPVs.

Influence of different SAR elicitors on induction and expression of PR-proteins in Potato and Muskmelon against Oomycete pathogens

Two cultivars each of potato namely; Kufri Badshah, Kufri Jyoti and muskmelon namely; Kajri and Punjab Hybrid were treated with varying concentrations of four different elicitors for induction of systemic acquired resistance (SAR) against Phytophthora infestans causing late blight in potato and Pseudoperonospora cubensis causing downy mildew in muskmelon. Attempts were made to induce SAR with application of various SAR elicitors as spray i.e. Jasmonic acid (JA), Salicylic acid (SA), Benzothiadiazole (BTH) and Beta Amino butyric acid (BABA). These elicitors were sprayed on 3-week-old sprouts and effect on defence related proteins along with late blight and downy mildew severity was studied. Leaf samples were collected up to 7 days post treatment and used for estimation of total proteins. Sporangial solution (4.0 × 104 sporangia per ml) was sprayed after 1 week of elicitors spray. Per cent disease severity was recorded at 14 days post inoculation. SA, JA, BTH and BABA caused statistically significant (at 5% level) increase in total soluble protein in leaf samples. The best treatments for maximum induction of proteins were 500 μM each of SA, JA, and BTH and 50 mM for BABA. SDS–PAGE electrophoresis confirmed that exogenous application of JA, SA, BABA and BTH resulted in the induction of PR proteins of low molecular size along with some other proteins in both potato and muskmelon, which helped in induction of SAR against oomycete pathogens.

Tetracyanobutadiene (TCBD) functionalized benzothiadiazole derivatives: effect of donor strength on the [2+2] cycloaddition–retroelectrocyclization reaction

A series of unsymmetrical and symmetrical mono/di 1,1,4,4-tetracyanobutadiene (TCBD) substituted benzothiadiazoles (BTDs) 2a–2g was synthesized by [2+2] cycloaddition–retroelectrocyclization reaction.

Systemic Resistance in Snap Bean (Phaseolus vulgaris L.) Elicited by Some Chemicals and Biotic Inducers Against White Mold Disease Caused by Sclerotinia sclerotiorum

The effect of chemicals and biotic inducers i.e., Bion [benzothiadiazole (BTH)], Salicylic acid (SA), Bacillus subtilis and Trichoderma harzianum as seed treatments of snap bean (Phaseolus vulgaris L. cv. Paulista.) compared to the fungicide Topsin M-70, were evaluated in the greenhouse and under field conditions during the two successive growing seasons 2016/2017 and 2017/2018 at Ashmoun, Menoufia Governorate, Egypt to control the white mold disease caused by Sclerotinia sclerotiorum (Lib.) de Bary. All the tested chemicals and biotic inducers treatments significantly reduced the percentages of pre- and post-emergence damping-off compared with the untreated control under greenhouse conditions. The highest percentage of survived plants was achieved by Topsin M-70 and Bion, followed by B. subtilis, Salicylic acid, and T. harzianum. Activities of defense-related enzymes peroxidase (PO), polyphenoloxidase (PPO) enzymes, and phenol content were determined. Bion treatment showed the highest increase in PO and PPO activity and total phenols followed by B. subtilis, Salicylic acid, and T. harzianum treatments in the presence of S. sclerotiorum. In the two successive growing seasons under field conditions, all the tested chemicals and biotic inducers treatments reduced the percentage of white mold incidence and severity of the treated snap bean plants compared with the untreated control. The highest reduction of disease incidence and severity was recorded by Topsin M-70 followed by Bion, B. subtilis, Salicylic acid,and T. harzianum, respectively. As well as, all treatments significantly increased vegetative characteristics i.e., plant height, No. of branches/plant, plant fresh and dry weight, and yield parameters i.e., average pod weight (g) and yield (ton/fed). Furthermore, chemical composition of green pods showed a significant increase in protein and carbohydrates content (%) beside all minerals Nitrogen (N), Phosphorus (P) and Potassium (K) content as compared with the untreated control in the two growing seasons.

Enhanced Photovoltaic Performance in D-π-A Copolymers Containing Triisopropylsilylethynyl-Substituted Dithienobenzodithiophene by Modulating the Electron-Deficient Units.

Three alternated D-π-A type 5,10-bis(triisopropylsilylethynyl)dithieno[2,3-d:2′,3′-d′]-benzo[1,2-b:4,5-b′]dithiophene (DTBDT-TIPS)-based semiconducting conjugated copolymers (CPs), PDTBDT-TIPS-DTBT-OD, PDTBDT-TIPS-DTFBT-OD, and PDTBDT-TIPS-DTNT-OD, bearing different A units, including benzothiadiazole (BT), 5,6-difluorinated-BT (FBT) and naphtho[1,2-c:5,6-c′]-bis[1,2,5]thiadiazole (NT), were designed and synthesized to investigate the impact of the variation in electron-deficient units on the properties of these photovoltaic polymers. It was exhibited that the down-shifted highest occupied molecular orbital energy level (EHOMO), the enhanced aggregation in both the chlorobenzene solution and the solid film, as well as the better molecular planarity, were achieved using methods involving fluorination and the replacement of BT with NT on the polymer backbone. The absorption profile was little changed upon fluorination; however, it was greatly broadened during replacement of BT with NT. Consequently, the optimized photovoltaic device based on the PDTBDT-TIPS-DTNT-OD exhibited synchronous enhancements in the open-circuit voltage (VOC) of 0.88 V, the short-circuit current density (JSC) of 7.21 mA cm−2, and the fill factor (FF) of 52.99%, resulting in a drastic elevation in the PCE by 129% to 3.37% compared to that of the PDTBDT-TIPS-DTBT-OD. This was triggered by PDTBDT-TIPS-DTNT-OD’s broadened absorption, deepened EHOMO, improved coplanarity, and enhanced SCLC mobility (which increased 3.9 times), as well as a favorable morphology of the active layer. Unfortunately, the corresponding PCE deteriorated after incorporating fluorine into the BT, due to the oversized aggregation and large phase separation morphology in the blend films, severely impairing its JSC. Our preliminary results demonstrated that the replacement of BT with NT in a D-π-A type polymer backbone was an effective strategy of tuning the molecular structure to achieve highly efficient polymer solar cells (PSCs).

Significant Influence of a Single Atom Change in Auxiliary Acceptor on Photovoltaic Properties of Porphyrin-Based Dye-Sensitized Solar Cells.

The rational design of porphyrin sensitizers is always crucial for dye-sensitized solar cells (DSSCs), since the change of only a single atom can have a significant influence on the photovoltaic performance. We incorporated the pyridothiadiazole group, as a stronger electron-withdrawing group, into the commonly well-established skeleton of D-porphyrin-triple bond-acceptor sensitizers by a single atom change for a well-known strong electron-withdrawing benzothiadiazole (BTD) unit as an auxiliary acceptor. The impact of the pyridothiadiazole group on the optical; electrochemical; and photovoltaic properties of D–π–A porphyrin sensitizers was investigated with comparison for a benzothiadiazole-substituted SGT-020 porphyrin. The pyridothiadiazole-substituted SGT-024 porphyrin dye was red-shifted so that the absorption range might be expected to achieve higher light harvest efficiency (LHE) than the SGT-020 porphyrin. However, all the devices were fabricated by utilizing SGT-020 and SGT-024, evaluated and found to achieve a cell efficiency of 10.3% for SGT-020-based DSSC but 4.2% for SGT-024-based DSSC under standard global AM 1.5G solar light conditions. The main reason is the lower charge collection efficiency of SGT-024-based DSSC than SGT-020-based DSSC, which can be attributed to the tilted dye adsorption mode on the TiO2 photoanode. This may allow for faster charge recombination, which eventually leads to lower Jsc, Voc and power conversion efficiency (PCE).

Benzothiadiazole, a plant defense inducer, negatively regulates sheath blight resistance in Brachypodium distachyon

Plant defense inducers that mimic functions of the plant immune hormone salicylic acid (SA) often affect plant growth. Although benzothiadiazole (BTH), a synthetic analog of SA, has been widely used to protect crops from diseases by inducing plant defense responses, we recently demonstrated that SA, but not BTH, confers resistance against Rhizoctonia solani, the causal agent of sheath blight disease, in Brachypodium distachyon. Here, we demonstrated that BTH compromised the resistance of Bd3-1 and Gaz4, the two sheath blight-resistant accessions of B. distachyon, which activate SA-dependent signaling following challenge by R. solani. Moreover, upon analyzing our published RNA-seq data from B. distachyon treated with SA or BTH, we found that BTH specifically induces expression of genes related to chloroplast function and jasmonic acid (JA) signaling, suggesting that BTH attenuates R. solani resistance by perturbing growth-defense trade-offs and/or by inducing a JA response that may increase susceptibility to R. solani. Our findings demonstrated that BTH does not work as a simple mimic of SA in B. distachyon, and consequently may presumably cause unfavorable side effects through the transcriptional alteration, particularly with respect to R. solani resistance.

Benzothiadiazole and nitrogen source modify the nitrogen metabolism in cucumber infected with Pseudomonas syringae pv. lachrymans

The influence of nitrogen source and benzothiadiazole (BTH) pretreatment on nitrogen metabolism-related enzyme activities was studied in cucumber plants infected with Pseudomonas syringae pv. lachrymans (Psl). The plants were grown hydroponically in media containing nitrate and urea at different ratios: 100% NO3− (100N), 75% NO3−/25% urea (75N) and 50% NO3−/50% urea (50N) and pretreated with BTH prior to Psl inoculation.In the presence of urea in the nutritional medium the activities of most enzymes in the control plants decreased. Disease development was influenced by nitrogen nutrition and the weakest symptoms occurred in the 75N plants. The BTH-induced disease restriction was dependent on the type of nitrogen nutrition and was most visible in the 50N plants (about 2-fold reduction of infected leaf area compared to the plants not pretreated with BTH). The nitrogen metabolism was modified by BTH and this effect was stronger than that of urea. Irrespective of the type of nitrogen nutrition, in the BTH-treated plants, the activities of nitrate reductase, ferredoxin- and NADH-dependent glutamate synthase decreased whereas those of NADH-dependent glutamate dehydrogenase (NADH-GDH), aminotransferases and NADP-dependent isocitrate dehydrogenase were enhanced compared to the controls. After infection, in all nutritional variants, the strongest effect of BTH pretreatment was observed for NADH-GDH on the 2 day, when its activity increased by 85–256% compared to the infected non-pretreated plants. Our results concerning the glutamate-metabolizing enzymes suggest that BTH treatment combined with low dose of urea may have a positive influence on the nitrogen management leading to the inhibition of disease symptom progress.

Influence of methyl jasmonate and benzothiadiazole on the composition of grape skin cell walls and wines.

Phenolic compounds are very important in crop plants, particularly in grapes. The different strategies to increase their levels include the use of elicitors such as methyl jasmonate (MeJ) and benzothiadiazole (BTH). In an attempt to improve the quality of wines, our aim was to evaluate the effect of preharvest application of these elicitors on the composition and structure of the skin cell walls of Monastrell, Merlot and Cabernet Sauvignon grapes, and to ascertain any relationship with the extractability of phenolic compounds during winemaking. The results indicated that the exogenous application of MeJ and BTH during veraison caused significant changes in several components of the skin cell walls, such as phenolic compounds, proteins and structural sugars. However these changes manifested themselves in different proportions in each variety and year, pointing to the varietal and meteorological dependence of the response to the application of these elicitors. The treatments delayed the maturation process in all varieties when rainfall was low. This observation, together with the observed increase in proteins and phenols in the skin cell wall of Monastrell and Cabernet Sauvignon, could contribute to the strength necessary to maintain the integrity of berries and to increasing resistance to fungal pathogens as the phenolic compounds evolve, thus improving the phenolic profile. However, the structural integrity of Merlot variety tended to decrease in the same conditions.

End-chain effects of non-fullerene acceptors on polymer solar cells

Abstract Four acceptor1-acceptor2-donor-acceptor2-acceptor1 (A1-A2-D-A2-A1) structural electron acceptors with different end-chains were designed and synthesized which all possessed indacenodithiophene (IDT) core, benzothiadiazole (BT) bridge as acceptor2, and rhodanine (R) end groups as acceptor1. The non-fullerene acceptor attached with ethyl group is called IDT-BT-R2 and used as control compound. And the other three of them are attached with methoxymethyl, trifluoroethyl and 1-piperidino groups generating IDT-BT-RO, IDT-BT-RF3 and IDT-BT-RN, respectively. The influence of end-chains on their optoelectronic properties were compared between four non-fullerene acceptors. Compared with IDT-BT-R2, the molecule IDT-BT-RF3 show red-shifted light absorption and lower LUMO level because of the electron withdrawing property of fluorine atoms. OSCs based on IDT-BT-RF3 display more efficient charge separation and lower degree of monomolecular recombination, allowing OSCs to show higher short-circuit current (Jsc) than the system of IDT-BT-R2. OSCs based on IDT-BT-RO also show more efficient charge separation and less monomolecular recombination. Due to the elevated LUMO level of the acceptor IDT-BT-RN, organic solar cells (OSCs) utilizing this material as acceptor display high open-circuit voltage (Voc) of 1.10 eV and low energy loss of 0.49 eV when maintaining a relatively high power conversion efficiency (PCE) of 7.09%. We demonstrated that the end-chain engineering could finely tune the light absorption properties and energy levels of novel non-fullerene acceptors and eventually improved OSCs performance can be harvested.

Theoretical insights into co-sensitization mechanism in Zn-porphyrin and Y123 co-sensitized solar cells

Donor-π-acceptor YD2-o-C8, WW-6, and SM315 are among best-performing Zn-porphyrins for their outstanding light-harvesting properties. To reach the further enhancement of photovoltaic performance of the corresponding cells, co-sensitization of these typical porphyrins with those dyes possessing intense absorption in the green spectral region (typically, Y123) is necessary. In this work, using density functional theory (DFT) and time-dependent DFT (TD-DFT) approaches, co-sensitization mechanism in the above three typical Y123/Zn-porphyrin systems has been systematically investigated. Moreover, due to the excellent performance of dithienosilole (DTS) group in organic dyes, it is designed here to replace the benzothiadiazole (BTD) unit in SM315 to give a new Zn-porphyrin dye designated SM315-1. This specific modification of SM315 can effectively retard the interfacial charge recombination compared to that in YD2-o-C8 and WW-6 cells by reducing the contact between oxidized porphyrins and injected electrons in TiO2 substrate, and simultaneously improves the overall light harvesting ability of the co-sensitized film with the theoretical maximum limit of photocurrent to be 38.31 mA/cm2. The both favorable aspects suggest an attractive application of the fully novel Y123/SM315-1 co-sensitized film in dye-sensitized solar cell (DSSC).

Preharvest Application of Elicitors to Monastrell Grapes: Impact on Wine Polysaccharide and Oligosaccharide Composition.

This work studied the effect of preharvest application in Monastrell grapes of four different elicitors [methyl jasmonate (MeJ), benzothiadiazole (BTH), chitosan from fungi (CHSf), and chitosan from seafood (CHSs)] on wine polysaccharide and oligosaccharide fractions. The polysaccharide and oligosaccharide fractions were isolated and characterized. Neutral monosaccharides were released after hydrolysis of polysaccharides and quantified by gas chromatography (GC). Sugar composition of oligosaccharides was determined after solvolysis by GC of their per-O-trimethylsilylated methyl glycoside derivatives. MeJ, BTH, CHSf, and particularly CHSs decrease the polysaccharide content in wine. The oligosaccharide concentration was also reduced after both CHS treatments. These results pointed to a lower degradation of the skin cell wall from treated grapes. We suggested that the cause would be a reinforcement of the skin cell wall as a result of the action of these elicitors. In conclusion, the application of any of these four elicitors in the clusters of the vineyard affected the complex carbohydrate composition of elaborated wine.

A2-A1-D-A1-A2 Type Non-Fullerene Acceptors with 2-(1,1-Dicyanomethylene)rhodanine as the Terminal Groups for Poly(3-hexylthiophene)-Based Organic Solar Cells.

2-(1,1-Dicyanomethylene)rhodanine (RCN) is an important electron-deficient terminal unit to build non-fullerene acceptors (NFAs) having been realized high power conversion efficiency (PCE) beyond 12% with complicated p-type polymer as electron donor. However, the photovoltaic properties of RCN-based NFAs are unsatisfied when paired with the classic p-type polymer poly(3-hexylthiophene) (P3HT). In order to make a contribution in this regard, we designed two RCN-based small molecular acceptors with A2-A1-D-A1-A2 structure, BT3 and BTA3, where benzothiadiazole (BT) and benzotriazole (BTA) are bridged A1 segments, respectively, to modulate the optoelectronic properties. As a result, P3HT:BTA3 solar cell exhibits a promising PCE of 5.64%, with a VOC of 0.90 V and a fill factor (FF) of 0.65, which is obviously much better than that of P3HT:BT3 (PCE = 2.55%, VOC = 0.72 V, FF = 0.61). The higher electron mobility of P3HT:BTA3 film indicates BTA3 tends to form a continuous pathway for electron transport even at a lower weight ratio of 1:0.3 than 1:0.5 for P3HT:BT3 film. Our results indicate that introducing a weak electron-withdrawing building block BTA is an effective strategy compared with the BT counterpart to improve the performance of RCN-based NFA devices.

Effects of Alkoxy and Fluorine Atom Substitution of Donor Molecules on the Morphology and Photovoltaic Performance of All Small Molecule Organic Solar Cells.

Two benzothiadiazole (BT)-based small-molecule donors, SM-BT-2OR with alkoxy side chain and SM-BT-2F with fluorine atom substitution, were designed and synthesized for investigating the effect of the substituents on the photovoltaic performance of the donor molecules in all small molecule organic solar cells (SM-OSCs). Compared to SM-BT-2OR, the film of SM-BT-2F exhibited red-shifted absorption and deeper HOMO level of −5.36 eV. When blending with n-type organic semiconductor (n-OS) acceptor IDIC, the as-cast devices displayed similar PCE values of 2.33 and 2.76% for the SM-BT-2OR and SM-BT-2F-based devices, respectively. The SM-BT-2OR-based devices with thermal annealing (TA) at 120°C for 10 min showed optimized PCE of 7.20%, however, the SM-BT-2F-based device displayed lower PCE after the TA treatment, which should be ascribed to the undesirable morphology and molecular orientation. Our results reveal that for the SM-OSCs, the substituent groups of small molecule donors have great impact on the film morphology, as well as the photovoltaic performance.

Theoretical Study of Effect of Introducing π-Conjugation on Efficiency of Dye-Sensitized Solar Cell.

In this study, phenoxazine (PXZ)-based dye sensitizers with triphenylamine (TPA) as a dual-electron donor and thiophen and benzothiadiazole (BTD) or 4,7-diethynylbenzo[c][1,2,5]thiadiazole (DEBT) as an electron acceptor (dye1, dye2, and dye3) were designed and investigated. dye3 can significantly stabilize the lowest unoccupied molecular orbital (LUMO) energy level of an organic dye. We used density functional theory (DFT) and time-dependent DFT (TD-DFT) calculations to better understand the factors responsible for the photovoltaic performance. The absorption spectrum of the dyes showed different forms because of the different energy levels of the molecular orbital (MO) of each dye and the intramolecular energy transfer (EnT). Among the three dyes, dye3 showed greater red-shift, broader absorption spectra, and higher molar extinction coefficient. These results indicate that adding a withdrawing unit and π-conjugation to a dye can result in good photovoltaic properties for dye-sensitized solar cells (DSSCs).

Alkyl Chain End Group Engineering of Small Molecule Acceptors for Non-Fullerene Organic Solar Cells

Alkyl chain engineering is widely used to prepare high-performance donor materials. However, relatively few studies have been focused on the alkyl chain optimization of acceptor materials. Herein, a series of new A–D–A (acceptor–donor–acceptor) type small molecule acceptors (ITBTR-C2, ITBTR-C4, ITBTR-C6, and ITBTR-C8) with indacenodithieno[3,2-b]thiophene (IDTT) as the core, benzothiadiazole (BT) as the π bridge, and ethyl-, butyl-, hexyl-, and octyl-substituted 2-(1,1-dicyanomethylene) rhodanine as the end groups, respectively, are successfully synthesized to systematically investigate the alkyl substituent effects on the physical, chemical, and electronic properties of A–D–A type small molecule acceptors. All molecules exhibit a strong and broad absorption from 600 to 800 nm as well as similar HOMO and LUMO energy levels. ITBTR-C6 with hexyl substitution shows the highest electron mobility and better phase separation morphology after blending with a donor polymer (PBDB-T). Therefore, inverted bulk heter...