LUMO Energy Levels Research Articles

Redox mediation through integrating chain extenders in active ionomer polyurethane hard segments in CdS quantum dot sensitized solar cell

Photovoltaic conversion efficiency is expressed as a function of hole extracting capacity of redox active group of electrolyte structure. Hard segment functionalized polyurethane ionomers have been developed as gel polyelectrolyte for photovoltaic reaction at the interfaces of photoanode/electrolyte/counter electrode in quantum dot sensitized solar cell. 3-mercaptopropeonic acid functionalized CdS quantum dot is synthesized and grown over the surface of titanium nanooxide via spin coating technique to work as photosensitizer. The hard segments (urethane linkages) are designed as negatively charged, short chain and covalently linked as –CH2CH2CH2SO3¯ (pendant anion) moiety. Different chemical and electronic environment affect hole transfer capacity around redox active group. The gel structure is realized as a conductive host as well as single ion transport electrolyte. The oxidized QDs (hole) are scavenged with redox active group available on the surface of hard segments. The electrical conductivities and thermal stability are controlled with composition of redox active group and the nature of chain extenders in polyurethane chain. The energy gap of HOMO and LUMO energy levels varies with the composition and electronic environment around polar pendant group. Electrical conductivity increases with functionalization level (anion concentration) grafted over urethane linkages. Charge transport behavior is controlled by tuning energy levels at the interfaces of photoanode/electrolyte matrix. The potential barrier is reduced by tuning redox potential of valance band (QDs) and HOMO (redox active ionomer). Photovoltaic performances are studied by varying chain structure and hole conducting environment around functionalized urethane linkage in ionomer framework. The device FTO/TiO2/MPA-CdS/SGO/SPU/Pt exhibits maximum photovoltaic conversion efficiency of 1.16% with soft segment modified oxygenic rich composite ionomer [S (PU + CB)-PCL-EDA] gel polyelectrolyte. Thus, redox active side chains easily recharge the oxidized quantum dot and accelerate photovoltaic reversible reaction due to adsorption of conducting carbon black on ionomeric chain.

Naphthalene imide derived BODIPY analogues as n-channel semiconductors

BODIPY analogues based on naphthalene mono-imides have been synthesized. The single-crystal X-ray diffraction studies provided evidences for their molecular structures, conformational features and stacking states. The effects of the boron difluoride chelation on the optical and redox properties of the dyes were investigated. The presence of difluoroboranyls in the naphthalene imides led to modifications in the electronic structure of the molecules. The LUMO energy level of the BF2-containing dye (NIPBF) was reduced by 0.15 eV in comparsion with naphthalene-diimides. The field-effect transistors devices based on the BODIPY analogues exhibited typical n-type behavior with electron mobility up to 0.10 cm2 V−1 s−1.

Molecular dynamic simulation and artificial intelligence of lead ions removal from aqueous solution using magnetic-ash-graphene oxide nanocomposite

In this work, the heavy metal ions (lead, Pb) adsorption process were studied using an artificial intelligence simulation based model for prediction of the adsorption process by using magnetic ash/graphene oxide (GO) nanocomposite. Also, the adsorption mechanism of Pb ions on the adsorbent were investigated using molecular dynamics (MD) calculations in aqueous solution. Reactivity of structures, ionization energy (I), electron affinity (A), chemical hardness (η), chemical softness (σ), and energy gap (ΔEgap) of all compounds were obtained from the HOMO–LUMO energy levels. The outcomes demonstrated that the adsorption of Pb ions on the adsorbent occurred through electrostatic interactions and van der waals bonding and the lead-water-GO configuration had the highest adsorption affinity according the ΔEgap calculations. The artificial neural network (ANN) with two hidden layers was used for developing the model with a mixture of linear and non-linear transfer functions. The equilibrium (Eq.) concentration of the Pb ion as an important factor in predicting the adsorption capacity of adsorbent was considered for the model output and initial Pb ion concentration as well as solution temperature were assumed as the model inputs. The training and validation procedure of ANN indicated great agreement between the experimental and predicted data according to the high coefficient of determination and low root mean square error (R2 > 0.999, RMSE = 0.086). Based on the simulation results increasing the initial concentration of Pb ion significantly affect the Eq. concentration while the solution temperature had a lower effect on Eq. concentration. The results of this study provide valuable model for pollutants removal. MD calculations and artificial intelligence simulation methods could be an appropriate combined technique for predicting the adsorption behavior of nanocomposite in heavy metal ions removal from the aqueous solution with high accuracy.

The Syntheses, Characterization and Field Effect Transistor Performance of Thiazole‐Based Dicyanomethylene‐Endcapped Quinoidal Compounds

AbstractThiazole‐based dicyanomethylene‐endcapped quinoidal compounds, QBTzTT8, QBTzTT16 and QBTzTT24 with different length of alkyl chains, were designed and synthesized. These compounds exhibit a relative low LUMO energy level of −4.55 eV, and can spontaneously react with metals Ag and Cu to form charge transfer complexes which is evidenced by Raman spectra, Infrared spectra and color change. Thin film transistors of QBTzTT16 and QBTzTT24 are fabricated, and metals Ag, Cu and Au are used as source‐drain electrodes. The devices display typical n‐type transistor performance. The mobility of devices shows nearly non‐dependent on source‐drain electrodes, being attributed to the spontaneously formed ultrathin charge‐transfer complex layer at the semiconductor/Cu (Ag) electrode interface. The average electron mobilities of QBTzTT16 and QBTzTT24 are 4.7×10−2 cm2 V−1 s−1 and 6.8×10−2 cm2 V−1 s−1, respectively.

New organic photosensitizers based on triphenylamine and hydantoin as anchoring group onto TiO2 Surface

In this work, we present the synthesis of novel D-π-A compounds based on the structure of 2-(3-hexyl-2-oxoimidazolin-4-ylidene) malononitrile, which can function as an acceptor group and anchoring group to the TiO2 surface. The synthetic route of the dyes involving a Knoevenagel condensation under microwave irradiation with donors based on triphenylamine (TPA) and thiophene moiety as a conjugated wire. Additionally, absorption, emission and electrochemical experiments were carried out to demonstrate a push-pull behavior in all the dyes.Finally, DCH 1-6 dyes were tested as photosensitizers in Grätzel type solar cells showing a low PCE values (between 0.10% and 0.60%), due to the poor electron injection on TiO2 surface for the low LUMO energy levels of the prepared dyes.

Dynamic Behaviors of Exciplex States in Rubrene/ C60 -Based OLEDs with Sub-Band-Gap Turn-On Electroluminescence

Although the origin of sub-band-gap electroluminescence has been extensively studied for organic light-emitting diodes (OLEDs) with a planar heterojunction of rubrene-fullerene (${\mathrm{C}}_{60}$), the dynamic behaviors of exciplexes formed at the $\mathrm{rubrene}/{\mathrm{C}}_{60}$ interface are still vague. Herein, employing magnetoconductance (MC) and magnetoelectroluminescence (MEL) detection techniques, we find an unreported reverse intersystem crossing (RISC, ${\mathrm{EX}}^{3}$ \ensuremath{\rightarrow} ${\mathrm{EX}}^{1}$) from triplet to singlet exciplexes dominated at the $\mathrm{rubrene}/{\mathrm{C}}_{60}$ interface. Besides this RISC evolution channel, the triplet exciplexes also participate in another two processes: one is the scattering channel of triplet-charge annihilation (TCASC, ${\mathrm{EX}}^{3}$ + $\stackrel{\ensuremath{\leftarrow}}{e}$ \ensuremath{\rightarrow} ${S}_{0}$+ \ensuremath{\downarrow}e) with excessive charge carriers, which is disadvantageous for RISC to occur, and the other is Dexter-energy transfer to produce a triplet exciton (${\mathrm{EX}}^{3}$ \ensuremath{\rightarrow} ${T}_{1}$) in rubrene followed by triplet-triplet annihilation (TTA, ${T}_{1}$+ ${T}_{1}$ \ensuremath{\rightarrow} ${S}_{1}$+ ${S}_{0}$ \ensuremath{\rightarrow} h\ensuremath{\nu}\ensuremath{\uparrow} + 2${S}_{0}$). This TTA is the physical origin of sub-band-gap EL because TTA needs no respective injection of electrons and holes into the LUMO and HOMO energy levels and requires no direct recombination of LUMO electrons with HOMO holes in rubrene. Moreover, both the bias-current dependences of MC and MEL traces reveal that the RISC process is more obvious in relatively balanced devices due to weak TCASC processes, and they show a monotonic decrease and nonmonotonic variation in unbalanced and relatively balanced $\mathrm{rubrene}/{\mathrm{C}}_{60}$-based OLEDs, respectively, because of the combined effects of the applied electrical field and the TCASC process. Theoretically, a stronger RISC process should be observed in devices by inserting a thin bathocuproine (BCP) interlayer to modify the $\mathrm{rubrene}/{\mathrm{C}}_{60}$ interface due to the increased separation distance between electron and hole in exciplex states, but the opposite experimental results are obtained because of strong TCASC channels simultaneously occurred with the insertion of a BCP interlayer. The RISC process decreases monotonically upon lowering the operational temperature due to its endothermic property. This work deepens our comprehensive understanding of the dynamic behaviors of exciplexes and the physical origin of sub-gap EL features in $\mathrm{rubrene}/{\mathrm{C}}_{60}$-based OLEDs.

Multistimuli-Responsive Fluorescent Switches Based on Reversible Decomposition and Regeneration of charge-transfer Complexes

Charge-transfer (CT) complexes of 4,4′-bis(9H-carbazol-9-yl)-1,1′-biphenyl (CBP) and three acceptors emitted cyan, green, and orange fluorescence, and lower LUMO energy levels of the acceptors prom...

A new cyclic carbonate enables high power/ low temperature lithium-ion batteries

The modern lithium-ion battery (LIB) configuration was enabled by the “magic chemistry” between ethylene carbonate (EC) and graphitic carbon anode. Despite the constant changes of cathode chemistries with improved energy densities, EC-graphite combination remained static during the last three decades. While the interphase generated by EC protects the fragile graphitic structure, the intrinsic disadvantages of EC (high viscosity, high melting point, excessive interphase growth) lead to mediocre power density and poor performances of LIB at sub-zero temperatures, where lithium depositions form upon charging. Such performance compromises arise from the fundamental dilemma between requiring effective interphase protection and high impedance from excessive growth of interphase. In this work, we designed and synthesized a “double EC” molecule as electrolyte additive to resolve the above dilemma. Erythritol bis(carbonate) (EBC) possesses lower LUMO energy level than EC and hence tends to decompose prior to EC reduction, but its weak solvation toward Li+ restricts the extent of its reduction, thus minimizing the interphase thickness and the corresponding impedances. Electrolytes containing EBC enables both the charging and discharging of ampere-size LIB pouch cells at sub-zero temperatures from 0 to -20℃, demonstrating that the key approach to improve low temperature performances lies in how to tailor interphasial chemistry rather than the bulk electrolyte composition.

Theoretical modelling of novel indandione-based donor molecules for organic solar cell applications

The development of efficient hole transport materials (HTMs) are highly attractive for the photovoltaic community to further improve the power conversion efficiency (PCE) and stability of organic solar cells. Therefore, in the present study, we have designed six new (H3T1-H3T6) small-molecule based HTMs for bulk-heterojunction (BHJ)-OSC. The photophysical characteristics and optoelectronic characterizations are systematically investigated. Density Functional Theory (DFT) and Time-Dependent Density Functional Theory (TD-DFT) are employed to study the arrangement of frontier molecular orbitals (FMOs), optical characteristics, open-circuit voltages, density of states, transition density matrix, and reorganization energies of holes and electrons. The designed materials (H3T1-H3T6) have shown a better absorption phenomenon that ranges maximum up to ∼563.00 nm and offering optical band gap at ∼2.10 eV. Additionally, all the designed materials have displayed a well-matched HOMO along with higher LUMO energy levels regarding PC61BM molecule. The calculations of H3T-2/PC61BM provide a deep insight about the charge shifting at the donor-acceptor (D-A) interface. The results of these theoretical characterizations have shown that an efficient molecular designing and strategy are prerequisite to get a desirable photovoltaic precursor best fitted for BHJ-OSCs. Thus, these modelled materials (H3T1-H3T6) are being suggested for synthesis and future development of efficient organic solar cell devices.

Solution Processable Pentafluorophenyl End‐Capped Dithienothiophene Organic Semiconductors for Hole‐Transporting Organic Field Effect Transistors

AbstractTwo solution‐processable organic semiconductors, DFPT‐DTTR (1) and DFPbT‐DTTR (2), composed of pentafluorophenyl (FP) end‐capped 3,5‐dialkyl dithienothiophene (DTTR) core with thiophene (T) or bithiophene (bT) as π‐bridged spacers are developed and investigated for their optical, electrochemical, microstructural, and electrical properties. With more conjugated bithiophene units, compound 2 exhibits a red‐shifted UV–vis absorption band and upshifted HOMO/downshifted LUMO energy levels. According to the density functional theory, compound 2 features a more twisted molecular structure due to the intrinsic non‐coplanar blocks in the π‐backbones. Compound 1‐based organic field effect transistors exhibit efficient hole transport with mobility up to 0.48 cm2 V−1 s−1. This is one of the high mobility organic semiconductors exhibiting p‐channel characteristics based on solution‐processable small molecular FP end‐capped fused/oligothiophenes. With large and interconnected crystalline morphologies, decreased π–π stacking distance, and less steric hindrance, compound 1 exhibits two orders of magnitude higher mobility than the more distorted 2, which exhibits lower hole mobility of 1.82 × 10−3 cm2 V−1 s−1.

Molecular dynamics and quantum simulation of different cationic dyes removal from contaminated water using UiO-66 (Zr)-(COOH)2 metal–organic framework

Metal organic frameworks (MOFs) especially benzene-1,4-dicarboxylic acid-functionalized UiO-66 (UiO-66-(COOH)2) with distinguished properties are great candidates for dyes removal from wastewater. In the current work organ-metal with anion groups, UiO-66-(COOH)2 (MOF/(COOH)2), was selected to adsorb four toxic cationic dyes from aqueous media. The quantum chemical calculations and molecular dynamic simulation were used to evaluate the adsorption mechanism of four toxic cationic dyes (malachite green (MG), methylene blue (MB), toluidine blue (TB) and crystal violet (CV)) on the MOF/(COOH)2 in the presence of water molecules. The optimized geometry of all structures was obtained through Dmol3 module. According to the obtained results the highest adsorption energy was obtained for CV-water-MOF/(COOH)2 configuration, while the MB-water-MOF/(COOH)2 had the lowest adsorption energy. Also, the molecular electrostatic potential maps and frontier molecular orbitals (FMO) were achieved for all configurations. The HOMO and LUMO as well as energy gap (ΔEGAP) indicated that the highest adsorption affinity was belong to CV-water-MOF/(COOH)2 configuration. Accordingly, the increasing of ΔEGAP was in the following order: CV-water-MOF/(COOH)2 < MG-water-MOF/(COOH)2 < TB-water-MOF/(COOH)2 < MB-water-MOF/(COOH)2.The quantum chemical descriptors such as chemical potential, electronegativity, nucleophilicity and electrophilicity index, chemical softness and hardness were obtained from HOMO and LUMO energy levels. Consequently, the results demonstrated that the chemical reactivity, softness, and polarizability of CV dye were higher compared to other studied dyes. The results of this theoretical revealed that UiO-66-(COOH)2 as an acidic group functionalized MOF is highly recommended for removal of cationic dyes. Molecular dynamic simulations can be a very useful approach to make a brighter insight about the mechanism of cationic dyes adsorption on the MOF adsorbent and very effective from perspective of time and experimental costs.

Molecular structure, quantum chemical and spectroscopic properties of 2,6–dibromonaphthalene by density functional theory calculations

In this work, the quantum chemical calculations were performed by means of the Gaussian09 packet program, using DFT in gas phase at the B3LYP level, with cc-pVDZ, cc-pVTZ, 6-31G(d,p) and 6-311G(d,p) basis sets. The most stable conformation of the 2,6–dibromonaphthalene (2,6–DBrN) molecule in free state was determined by the Spartan'14 program. The vibrational frequencies have been calculated at the same level of theory. These frequencies were calculated and scaled, and then values have been compared with the experimental Infrared and Raman spectra. The vibrational modes were determined based on TED analysis on the basis of 6-311G(d,p) using the SQM program. Theoretical 13C–NMR and 1H–NMR chemical shifts of the 2,6–DBrN molecule were calculated in DMSO and were compared the experimental values. NBO analysis study of 2,6–DBrN was performed to investigate charge transfer as well as to analyzed intra- and interactions. The HOMO and LUMO energy levels of the 2,6–DBrN molecule were determined. Besides, molecular electrostatic potential (MEP) maps of the studied molecule were made using the DFT method. Since the apparent absorption maxima of the molecules correspond to the electron transitions between the boundary orbitals corresponding to the HOMO–LUMO energies, these transitions were analyzed by UV/Visible spectroscopy.

Organic dyes based on selenophene for efficient dye-sensitized solar cell.

The investigation of dye-sensitized solar cells (DSSCs) based on different donor groups linked with cyanoacrylic acid electron acceptor by Selenophene as π-bridged (D-π-A) was performed based on density functional theory (DFT) time-dependent DFT (TDDFT). Different functional were tested W97XD, PBEPBE, CAM-B3LYP, and B3PW91, and compared with experimental results of the reference D1. The theoretical results with CAM-B3LYP functional at 6-311G (d,p) basis sets were capable of predicting the absorption maximum that has been reported experimentally. Calculations were made to establish the conformational orientation of the cyanoacrylic acid group and evaluate the effect of changing donor units' on the electronic properties of the ground state. Structural and electronic properties, along with the photovoltaic properties, were investigated. The LUMO and HOMO energy levels of these dyes can positively affect the process of electron injection and dye regeneration. Light-harvesting efficiency (LHE), injection driving force (ΔGinject), and total reorganization energy (total) were also discussed. To further support the previous proprieties, electronic excited state energies were obtained by TDDFT// CAM-B3LYP/6-311G(d,p) calculations. The calculated results of these dyes reveal that D8 dye possessing triphenylamine donor unit has the best electronic, optical properties, and photovoltaic parameters.

Synthesis, optical dye properties and band gap energies of silver hydroxy-aryl thiazolo[5,4-d]thiazole complexes

In the present work, phenyl-, o‑hydroxy phenyl-, o,p‑hydroxy phenyl-, p‑hydroxy phenyl- and o‑hydroxy naphtyl-thiazolo[5,4-d]thiazole dye molecules and their silver complexes were synthesized. The optical microscopy, UV–vis. absorption spectroscopy, FT-IR spectroscopy, cyclic voltammetry (CV) and the band energies of the synthesized aryl / hydroxy aryl thiazolo[5,4-d]thiazole molecules and their silver complexes were studied. The HOMO and LUMO energy levels were obtained from the CV voltammograms. The optical band gap (EgOpt.) and the electrochemical band gap (EgCV) energies were calculated from the UV–vis. absorption and CV, respectively. It was found that the presence of the hydroxy aryl groups of thiazolo[5,4-d]thiazole unit and the silver coordination have changed the UV–vis. absorption spectra and the band gap energies of the thiazolo[5,4-d]thiazole molecules. Among the studied thiazolo[5,4-d]thiazole molecules and their silver complexes, the band gap energies were obtained as Egopt = 2.07 eV and EgCV = 1.67 eV for silver bis(p‑hydroxy-pheyl)-thiazolo[5,4-d]thiazole (Ag2[p-(OH)2-Ph2TT]), and Egopt = 2.07 eV and EgCV = 1.31 eV for bis(o‑hydroxy-napthyl)-thiazolo[5,4-d]thiazole (Ag2[o-(OH)2Naph2TT]) complexes. As a result, these thiazolo[5,4-d]thiazole molecules and their silver complexes are possible canditate dye materials for the photovoltaic solar cells.

Two asymmetrical perylene diimide derivatives: Synthesis, optical-electrochemical properties and morphologies of self-assembly

Perylene diimides (PDIs) belong to an important class of photoactive materials due to their excellent electrical and photophysical properties. Highly controlled aggregation and self-assembly attributed to the large π-conjugated aromatic scaffold have led to a variety of optoelectronic applications. In this manuscript, two PDI derivatives PDI-1 and PDI-2 with unsymmetrical N-substitution of amine and ester-bridge were designed and synthesized. These two compounds were characterized by NMR, Fourier transform infrared (FT-IR), and high-resolution mass spectrometry (HRMS). The photophysical properties were studied by UV–Vis absorption and fluorescence spectroscopy. Cyclic voltammograms of PDI-1 and PDI-2 were investigated and HOMO and LUMO energy levels of both two PDIs were estimated as −6.2 and −3.9 ​eV, respectively. Thermal properties were also studied by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). PDI-1 was assembled into nanotubes while PDI-2 was assembled into nanobelts respectively, via a reprecipitation method. PDI-1 and PDI-2 show good potential application in organic devices such as solar cells, organic field-effect transistors (OFETs) and so on.

Development of new nonacyclic small-molecule acceptors involving two benzo[1,2-b:4,5-b′]dithiophene moieties for efficient polymer solar cells

Benzo[1,2-b:4,5-b′]dithiophene (BDT) is demonstrated as a very effective building block to construct acceptor-donor-acceptor (A-D-A) small-molecule acceptors (SMAs) involving one BDT unit for high-performance polymer solar cells (PSCs). Herein, we successfully developed two new A-D-A SMAs, namely IDBDT-O and IDBDT-T, with the same BDT-fused nonacyclic indacenobis(benzo[1,2-b:4,5-b′]dithiophene) (IDBDT) central D unit and 1,1-dicyanomethylene-3-indanone (IC) terminal A group, but different side chains (alkoxyl vs alkylthiophene) attached on the BDT units. The IDBDT central core is formed by the fusion of one indacene segment and two BDT moieties, which obviously differs from the previously studied BDT-fused SMAs. Compared to IDBDT-T with alkylthiophene side chains, IDBDT-O with alkoxyl side chains exhibits a broader absorption, smaller band gap, and higher-lying HOMO energy level. Moreover, these IDBDT-based SMAs have upshifted LUMO energy levels relative to the reported BDT-fused SMAs, which is beneficial to increase open-circuit voltage (Voc). Bulk-heterojunction PSCs fabricated from polymer donor PBDB-T and IDBDT-T achieve the best power conversion efficiency (PCE) of 7.14% with a high Voc of 0.96 V, a short-circuit current density (Jsc) of 15.20 mA cm−2, much larger than a PCE of 1.83%, a Voc of 0.89 V and a Jsc of 5.21 mA cm−2 for the counterpart of PBDB-T:IDBDT-O. The enhanced device performance could be ascribed to higher and more balanced carrier mobility, more efficient exciton dissociation, and weaker bimolecular recombination as well as better active layer morphology in the IDBDT-T-based PSCs relative to IDBDT-O. Our results provide a new molecular design strategy to exploit BDT-fused A-D-A SMAs for high-performance PSCs.

Pd (II) complexes bearing “SNS” pincer‐type thioether ligands: Application as catalysts in the synthesis of vitamin K3

The novel four SNS pincer‐type thioether containing Pd (II) complexes were synthesized and characterized by using FT‐IR, UV‐Vis, mass, elemental analysis techniques. The complexes were used as catalysts in the synthesis of vitamin K3 (2‐methyl‐1,4‐naphthoquinone) from 2‐methyl naphthalene. Hydrogen peroxide was used as green oxidant in acetic acid and sulfuric acid medium. L2‐Pd (II) and L3‐Pd (II) complexes showed the best catalytic activity with 62.63% and 61.05% selectivities in the conversions of 82.61% and 87.84%, respectively. Moreover, in silico studies on Pd (II) complexes have shown that L2‐Pd (II) and L3‐Pd (II) complexes have low band gaps between LUMO and HOMO energy levels and their electrostatic energy values are higher than other complex structures. This reveals that they have better chemical activity than other complexes and also supports the experimental studies carried out in this research. The conversions and the selectivities of these complexes are one of the best compared to the literature. Peroxyacetic acid with sulfuric acid is a very important oxidant in the oxidation of 2‐methyl naphthalene to 2‐methyl‐1,4‐naphthoquinone.

Thiophene with Oligoethylene Oxide Side Chain Enables Random Terpolymer Acceptor to Achieve Efficient All‐Polymer Solar Cells

AbstractThe development of high‐performance polymer acceptors is the key challenge for all‐polymer solar cells (All‐PSCs), especially related morphology control in the blend film. Herein, we introduce a thiophene with oligoethylene oxide side chain (TOE) as the third unit into a D‐A copolymer PYT by simple random polymerization. Rigid‐fused unit Y5 with large planar or quasi‐plane surfaces are partially substituted to obtain a series of novel random terpolymers PYT‐TOE(x) (x represents the molar ratio of TOE unit). The electron‐deficient unit Y5 partly replaced by electron‐rich unit TOE realizes the increase of LUMO energy levels. More importantly, a moderate amount loading of TOE not only modulate the polymer acceptor solubility and molecule arrangement, but also perfect the compatibility between the polymer donor and acceptor. Thus, optimized crystallinity and π‐π stacking of blend film are obtained, which is favorable for charge transfer and better film morphology. Eventually, accompanied by improved JSC, VOC and FF simultaneously, the device photoelectric conversion efficiency (PCE) increase from 11.75 % for PBDB‐T:PYT to 12.77 % for PBDB‐T:PYT‐TOE(10). These results indicate that the random ternary copolymerization of small molecule acceptor with functional third unit TOE is a simple but effective strategy to develop polymer acceptors for high‐efficiency All‐PSCs.

Phenanthroimidazole substituted imidazo[1,2-a]pyridine derivatives for deep-blue electroluminescence with CIEy ∼ 0.08

Blue emitting materials with balanced charge carrying capacity are crucial for effective OLED. Phenanthroimidazole based deep blue materials are developed with a donor–acceptor configuration to optimize charge balance in OLEDs. In this work, three new dipolar materials based on the phenanthroimidazole-imidazopyridine conjugated system were synthesized and characterized. The position and number of phenanthroimidazole substituents are changed to study structure property relationships. All derivatives carried superb thermal stability and high photoluminescence quantum yield. Dyesin which phenanthroimidazole chromophore linked at thepara-position of C2 phenyl ring showed the red-shifted emission band. The positive solvatochromism was observed with the increase of solvent polarity, associated with the intramolecular charge transfer at excited state. The electrochemical measurement revealed that the fluorophores have low-lying LUMO energy levels. Further, doped devices were fabricated with these emitters to estimate the EL performances. Among all the emitters, the doped device fabricated with a dye containing phenanthroimidazole chromophore at para-position of C2 phenyl showed superior electroluminescence performance with CIE coordinates (0.16, 0.08).

12Н-quinoxaline[2,3-b]phenoxazines: Synthesis, optical, electrochemical properties and insight into photovoltaic application

A series of N-aryl derivatives of heteropentacyclic 12Н-quinoxaline[2,3-b]phenoxazine (QOPO) system were synthesized and spectral, luminescent, electrochemical and optoelectronic properties of the prepared compounds studied. The compounds are well soluble in nonpolar and polar solvents, absorb in the strongest emissive part of the solar spectrum and exhibit sufficiently high photostability at air conditions. The HOMO, LUMO energy levels of the obtained QOPOs were calculated by the DFT B3LYP/6–311++G(d,p) method and assessed using the electrochemical methodology. The double-layered p-n heterojunction organic solar cells constructed on the basis of QOPOs as electron donor components, bathocuproine as the exciton blocking layer and fullerene C60 as electron acceptor displayed promising values of photovoltaic (open circuit voltage and short-circuit current density) parameters.