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For precipitation-strengthened Al alloys, the interfacial segregation behavior of alloying elements plays an important role in controlling the effectiveness of precipitation strengthening. In this work, the adhesion work (Wad) and interfacial energy (γ) of the η(0001)/Al(111) interface were studied to gain an insight into the interface properties between the precipitate η and the Al matrix. Additionally, we examined the impact of the segregation behavior of alloyed elements on the bonding strength of the interface. The computed values for Wad and interfacial energies indicated that the T6S3 terminated configuration represents the interfacial structure with the highest stability across all models analyzed. Focusing on the T6S3 interface, the assessed segregated energies (Eseg) disclose that the segregation ability of elements from strong to weak exhibits the order of Ti > Sc > Zr > Y > Ta > Nb > Lu > Hf > Mo > V > W, while Cr and Mn elements are not easy to segregate at the interface. Sc, Ti, V, Cr, Mn, Zr, Nb, Mo, Hf, and Ta preferentially occupy Al atoms, whereas Y and Lu predominantly inhabit Mg atoms. Relative to the clean interface, the electron cloud enrichment at the interface after alloying element X (Zr, Sc, Ti, W, Hf, Mn, Y, Lu and V) doping is weakened, and the ion interaction among interface atoms is enhanced. After doping alloying element X (Nb, Mo, Ta, and Cr), the degree of electron cloud enrichment at the interface is obviously enhanced, and the covalent interaction among interface atoms is enhanced. This suggests that the introduction of alloyed elements through doping can augment the bond strength at the interface between the precipitated phase and matrix, thereby reinforcing the strength and toughness of 7xxx series alloys. [ABSTRACT FROM AUTHOR]

This paper constructs a single O and S functionalized Zr2N model for surface levelling and at the same time a series of bifunctional models with different functional group ratios and distributions. The influence of these functional groups on the electrochemical and lithium storage properties of Zr2N materials has been systematically investigated in terms of lithium atom adsorption, migration and lithium storage capacity. Among them, the theoretical lithium storage capacities of Zr2NO2 and Zr2NS2 with a low migration barrier are more than 755.02 and 678.30 mA h g−1, respectively. The results show that the O and S-functionalized Zr2N materials are all metallic and capable of adsorbing a certain number of lithium atoms. By controlling the ratio and distribution of the O and S functional groups, the adsorption position and adsorption energy of the lithium atoms can be influenced to a certain extent. Especially, the aim of improving the lithium storage performance of the material can be achieved in this way. [ABSTRACT FROM AUTHOR]

Gradient induced unusual strain hardening achieves the equilibrium of the strength and plasticity of alloys, and is an important strategy for the optimization of the mechanical properties of metals and alloys. The segregation of solute elements can greatly improve the grain boundary stability, inhibit grain coarsening and promote the mechanical strength of the alloy. In our efforts, the segregation structure of the solute element Co was designed and added to the gradient nano Ni–Co alloy, and the two strengthening strategies were applied simultaneously in one structure. The mechanical strength of the alloy achieved a second increase based on the unique combination of gradient induced strain hardening and high plasticity, especially the yield strength of alloy increase amplitude reach to 42%. This provides a positive direction for the alloy strengthening strategy. In the process of secondary strengthening, the micro-mechanism is divided into two stages: in the first stage, the gradient strain provides the alloy with geometrically necessary dislocations and a multi-axial stress state, and the existence of large numbers of geometrically necessary dislocations creates good conditions for the second stage strengthening. In the second stage, the solute segregation induced stable grain boundaries produce a strong pinning effect on the geometrically necessary dislocation, which realizes the coupling of grain boundary strengthening and dislocation strengthening. This provides a new strengthening strategy and positive theoretical guidance for the experimental preparation of advanced alloys with excellent properties. [ABSTRACT FROM AUTHOR]

The electronic structure and photocatalytic performance of GaSe/MoSSe and Ga2SSe/MoS2 heterojunctions are systematically investigated by means of first-principles calculations. The outcomes demonstrate that the IV and II stacking patterns feature the lowest binding energies and the shortest interlayer spacing, wherein the A stacking configurations show typical type-II band alignment characteristics which are conducive to fulfill effective separation of electron–hole pairs in space. The electrostatic potential and the CDD indicate the generation of built-in electric fields from MoSSe to GaSe layers and from Ga2SSe to MoS2 layers, respectively, in the interfacial domain, providing a theoretical basis for the examination of the photocatalytic mechanism. The two heterojunctions are more preferable for the photocatalytic decomposition of water under acidic and neutral atmospheres at dissimilar pH levels. For the GaSe/MoSSe heterojunction, the band gap follows a monotonic decreasing tendency when the tensile strain increases from 0% to 6%, while in the case of compressive strain, the band gap increases and then decreases, and the heterojunction cannot undertake the water oxidation process when the tensile strain surpasses 2%. Meanwhile, when a compressive strain of 0% to 3% is imposed, the heterojunction redox potential always traverses the redox potential of water, wherein the photocatalytic performance is sustained. For the Ga2SSe/MoS2 system, the band gap value decreases monotonically with the exertion of both tensile and compressive strains. Moreover, it is applicable to photocatalytic water decomposition in the strain range of −6% to 6%. The absorption coefficients reveal that the two heterojunction system has a higher peak in the visible range than the corresponding monolayer, indicating a higher light absorption intensity. Furthermore, the electron mobility of heterojunctions along both directions is significantly higher than that of MoS2 and WSe2 monolayers, and GaSe/HfS2 and K2Se/Cs2S heterojunctions. These findings propose that both GaSe/MoSSe and Ga2SSe/MoS2 heterojunctions can be utilized as potentially better catalysts for the photocatalytic decomposition of water. [ABSTRACT FROM AUTHOR]

Donor engineering plays an important role in tuning the intramolecular charge transfer (ICT) interactions of donor–acceptor (D–A) molecules and the related performance in the further applications. In comparison to the complicated and time-consuming molecular skeleton exploitation, optimization of the donor number and the substitution position is more facile and efficient. Herein, different quantities of diphenylamine (DPA) units are incorporated into the tris(2,4,6-trichlorophenyl)methyl (TTM) radicals from various directions. The effects of the donor number and the substitution position on the ICT interactions and the photothermal conversion performance are investigated. It is found that TTM-DPA (644 nm), TTM-2DPA (650 nm), and TTM-3DPA (637 nm) with various DPA units attached on different arms of the TTM core exhibit similar absorption maxima and high photoluminescence (PL) quantum yields (over 56%) in cyclohexane solutions. However, when multi-DPA units are introduced on the unilateral arm of the TTM unit, the absorption maximum red shifts to 675 nm for TTM-BDPA and 717 nm for TTM-TDPA. Meanwhile, no obvious PL can be detected using a spectrometer. The near-infrared (NIR) absorbance and the nonradiative transition of the TTM radicals contribute to their photothermal conversion. Consequently, remarkable photothermal conversion efficiencies of 41% and 50% are achieved for TTM-BDPA and TTM-TDPA, respectively. Our study provides an alternative design rule for controlling the ICT effect and shows that organic radicals have potential for application in photothermal therapy in the near future. [ABSTRACT FROM AUTHOR]

Two types of thiophene derivatives, i.e., thiophene (T) and 3,4-ethylenedioxylthiophene (ET) with a single thiophene ring, and thieno[3,2-b]thiophene (TT) and 2,2′-bithiophene (BT) with double thiophene rings, have been inserted between the two pyridinium units of an octyl viologen (V). The effective conjugation lengths of the resulting thienoviologens TV, ETV, TTV, and BTV have been successfully extended. Unlike a traditional alkyl viologen, which always serves as a fluorescence quencher, all four thienoviologens exhibit intense photoluminescence (PL). The bathochromic shifts in both absorption and PL spectra are more pronounced in TTV and BTV with double thiophene rings as compared with TV and ETV with a single thiophene bridge. Moreover, upon applying a negative potential, all four thienoviologens display significant changes in both absorption and PL spectra, indicating their electrochromic (EC) and electrofluorochromic (EFC) properties. Additionally, the EC response can be found not only in the visible but also in the near-infrared (NIR) region. Although TTV and BTV with longer conjugated bridges exhibit more extended effective conjugation lengths and higher PL quantum yields, the EC and EFC devices based on TV and ETV gels display better performance than that for TTV and BTV owing to the faster charge and mass transport for smaller molecules. Consequently, a better comprehensive property is achieved by the ETV-based gel, which demonstrates fast coloration (1.9 s), high color contrast (87%), and high coloration efficiency (521 cm2 C−1) in the EC device with high fluorescence contrast ratio (Ion/Ioff = 221) in the EFC device. Furthermore, two smart windows have been fabricated to utilize their different driving potentials. Upon increasing the potential, the "window flower" in the first device blossoms out with gradually changing petal colors, while the other dual-functional smart window can be adjusted between flower decoration and light blocking functions. [ABSTRACT FROM AUTHOR]

A heterocycloarene derivative (S-Octulene) possessing two sulfur atoms was conveniently synthesized through Bi(OTf)3-catalyzed cyclization from a macrocyclic tetramethoxyethenylated precursor. The physical properties of S-Octulene and its supramolecular host–guest interaction with C60 and C70 were investigated by fluorescence titration and 1H NMR. The solution-processed organic field-effect transistor (OFET) measurements demonstrated that S-Octulene behaved as a p-type semiconductor with a hole mobility exceeding 0.01 cm2 V−1 s−1. Our findings pave a new path to design novel heterocycloarenes for the development of host–guest chemistry and organic semiconductors. [ABSTRACT FROM AUTHOR]

A highly π-acidic dipyridinium-naphthalene diimide acceptor shows anion–π interactions with halides and PF6−. Lewis basicity and redox potential of the anion affect the chemistry, and photophysical and electrochemical properties, as well as both ionic and electrical conductivities. Our results provide insights into doping, degradation and ion transport mechanisms in organic n-type semiconductors. [ABSTRACT FROM AUTHOR]

Open-shell π-conjugated compounds have recently received intense attention due to their unique properties and promising applications in materials science. However, the experiments on how the substituents affect their chemical bonding and structural motif remain less addressed. In this work, a series of tetrabenzo-Chichibabin's hydrocarbon (TBC) derivatives substituted by different electron-donating or -withdrawing groups at the termini were synthesized. The substituent effect was studied via X-ray crystallographic analysis. The strong electron-donating dimethylamino-group substituted TBC derivative underwent simultaneous oxidation to give two cyanine-like moieties at the termini. More interestingly, it exhibited unusual thermochromic and thermomagnetic behaviours. [ABSTRACT FROM AUTHOR]

In this Feature Article, we highlight our recent efforts toward stable open-shell singlet diradicaloids and polyradicaloids. A brief review on the historical works in the area is introduced first, followed by discussion on the fundamental electronic and physical properties of open-shell singlet diradicaloids. Then, the structure–diradical character relationships based on our recently developed diradicaloids are presented. Next, the challenges and solutions toward stable polyradicaloids and 3D π-conjugated diradicaloids are discussed. Finally, their preliminary material applications are introduced and a perspective view of the area is given. [ABSTRACT FROM AUTHOR]

To obtain a broad spectral response in the visible region, TiO2 film is co-sensitized with a porphyrin dye (FNE57 or FNE59) and an organic dye (FNE46). It is found that the stepwise co-sensitization in one single dye solution followed by in another single dye solution is better than the co-sensitization in a cocktail solution in terms of photovoltaic performance. The stepwise co-sensitization first with a porphyrin dye and then with an organic dye outperforms that in a reverse order. DSSC devices based on co-sensitizers FNE57 + FNE46 and FNE59 + FNE46 with a quasi-solid-state gel electrolyte generate power conversion efficiencies of 7.88% and 8.14%, respectively, which exhibits remarkable efficiency improvements of 61% and 35%, as compared with devices sensitized with the porphyrin dyes FNE57 and FNE59, respectively. Co-sensitization brings about a much improved short-circuit photocurrent due to the complementary absorption of the two sensitizers. The observed enhancement of incident monochromatic photon-to-electron conversion efficiency from individual dye sensitization to co-sensitization is attributed to the improved charge collection efficiency rather than to the light harvesting efficiency. Interestingly, the open-circuit photovoltage for the co-sensitization system comes between the higher voltage for the porphyrin dye (FNE57 or FNE59) and the lower voltage for the organic dye (FNE46), which is well correlated with their electron lifetimes. This finding indicates that not only the spectral complementation but also the electron lifetime should be considered to select dyes for co-sensitization. [ABSTRACT FROM AUTHOR]

A series of D–(π)–A′–π–A featured organic dyes with different numbers of 3,4-ethylenedioxythiophene (EDOT) bridges and different anchoring groups, i.e., cyanoacrylic acid or rhodanine-3-acetic acid, have been designed and synthesized for application in quasi-solid-state dye-sensitized solar cells (DSSCs). The absorption, electrochemical and photovoltaic properties are systematically investigated. Upon the incorporation of an auxiliary EDOT unit into sensitizers FNE60 and FNE61 with D–A′–π–A configuration, sensitizers FNE62 and FNE63 with D–π–A′–π–A configuration exhibit much broader absorption spectra, which is beneficial to the light-harvesting capability and photocurrent generation. When the cyanoacrylic acid group in sensitizers FNE60 and FNE62 is replaced by a much stronger electron-withdrawing group, rhodanine-3-acetic acid, strengthened intramolecular charge transfer interactions are realized, which results in the significantly bathochromically shifted maximum absorption wavelengths for sensitizers FNE61 and FNE63. However, the methylene group in the rhodanine-3-acetic acid unit interrupts the LUMO delocalization on the anchoring group in sensitizers FNE61 and FNE63, as revealed by theoretical calculation, which may result in less effective electron injection from the LUMO to the conduction band of the titania semiconductor. Consequently, the quasi-solid-state DSSC based on FNE62 exhibits a highest power conversion efficiency of 8.2%, which illustrates good long-term stability after continuous light soaking for 1000 h. [ABSTRACT FROM AUTHOR]

Two novel organic sensitizers (FNE55 and FNE56) containing a 6,7-difluoroquinoxaline moiety have been designed and synthesized for quasi-solid-state dye-sensitized solar cells (DSSCs). For comparison, an organic dye, FNE54, without fluorine has also been synthesized. The effects of the introduction of fluorine on the absorption, electrochemical and photovoltaic properties have been systematically investigated. Upon the incorporation of fluorine in the quinoxaline unit, the electron-withdrawing ability is strengthened, which results in the enhanced push–pull interactions and thus narrows the energy band gap. The absorption maximum wavelength in toluene solution bathochromically shifts from 504 nm for FNE54 to 511 nm for FNE55, and further to 525 nm for FNE56. However, although the lowest unoccupied molecular orbitals (LUMOs) are lowered down after the introduction of fluorines, the driving force for the photo-excited electrons from their excited states to the semiconductor conduction band is still sufficient. Consequently, the quasi-solid-state DSSC based on FNE56 exhibits a highest power conversion efficiency of 8.2%, which is 37% higher than that for FNE54 based quasi-solid-state DSSCs. [ABSTRACT FROM AUTHOR]

Three double D-π-A branched organic dye isomers (D1, D2, and D3) with octyloxy bridge linked at different positions of the π-bridge in the D-π-A branch have been designed and synthesized for dye-sensitized solar cells (DSSCs). Their photophysical, electrochemical, and photovoltaic properties were further investigated. Compared with the reference dye isomers containing single D-π-A branches, the double D-π-A branched dye isomers consisting of two separated light-harvesting moieties in one molecule are beneficial to photocurrent generation. Moreover, the cross structure of the double D-π-A branched organic dye isomers is superior to the rod structure of the dye isomers with single D-π-A branches in the suppression of intermolecular interactions, which results in reduced charge recombination rates in the DSSCs based on double branched organic dye isomers. Therefore, in comparison to the DSSCs based on isomeric dyes with single D-π-A branches, the DSSCs based on double branched organic dye isomers display both improved short-circuit current and open-circuit voltage. Furthermore, similar to the single D-π-A branched organic dye isomers, those isomeric dyes with double D-π-A branches exhibit slightly different photophysical properties, which result in the varied photovoltaic performance. The highest power conversion efficiency of 8.1% and 6.9%, respectively, is achieved for isomer D1 based DSSC with liquid and quasi-solid-state electrolyte under simulated AM1.5G solar irradiation (100 mW cm-2). [ABSTRACT FROM AUTHOR]

Molecular dynamics simulations were performed to clarify the nanomechanical responses of β-Si3N4 nano-thin layers in the basal plane for indenters of various radii, different indentation velocities and at different temperatures. It was found that the maximum loading stress and indenter displacement both increase with increasing radius of the indenter. A large number of N6h–Si bond-breaking defects and one N2c–Si bond-breaking defects are responsible for the initiation of fracturing. With increasing loading velocity, the maximum loading stresses show almost no change; however, a high loading velocity can shorten the displacement of the indenter and contributes to the formation of new N2c–Si bond-breaking defects. Thermal fluctuations can decrease the mechanical properties of the thin layer. The maximum loading stresses and indenter displacements are sensitive to both the radius of the indenter and the loading temperature. [ABSTRACT FROM AUTHOR]

Molecular dynamics simulations are performed to clarify the extreme strain rate and temperature dependence of the mechanical behaviors of nano silicon nitride thin layers in a basal plane under tension. It is found that fracture stresses show almost no change with increasing strain rate. However, fracture strains decrease gradually due to the appearance of additional N2c–Si bond breaking defects in the deformation process. With increasing loading temperature, there is a noticeable drop in fracture stress and fracture strain. In the low temperature range, roughness phases can be observed owing to a combination of factors such as configuration evolution and energy change. [ABSTRACT FROM AUTHOR]

Two novel X-shaped organic sensitizers (FNE48 and FNE49) with a quinoxaline bridge have been designed and synthesized. The structural difference between the two sensitizers is the number of anchoring groups. The relationship between the chemical structures and their optoelectronic properties has been systematically investigated. It is found that a broader and more intense charge transfer band is observed for sensitizer FNE48, with a single anchoring group, in comparison to sensitizer FNE49, which contains twin anchoring groups. Consequently, a high power conversion efficiency (η) of 6.2% is achieved for a dye-sensitized solar cell (DSSC) based on sensitizer FNE48 using a liquid electrolyte. Moreover, a η of 5.2% is obtained for a quasi-solid-state DSSC based on sensitizer FNE48 and this remains at 100% of the initial value after continuous light irradiation for 1500 h. [ABSTRACT FROM AUTHOR]

Two novel cross-conjugated isomers based on 4,8-dithienylbenzo[1,2-b:4,5-b′]dithiophene have been designed and successfully synthesized. It was found that the charge transfer interaction was much stronger in the benzodithiophene direction as compared with the other perpendicular direction. [ABSTRACT FROM AUTHOR]

For precipitation-strengthened Al alloys, the interfacial segregation behavior of alloying elements plays an important role in controlling the effectiveness of precipitation strengthening. In this work, the adhesion work ( W ad ) and interfacial energy ( γ ) of the η(0001)/Al(111) interface were studied to gain an insight into the interface properties between the precipitate η and the Al matrix. Additionally, we examined the impact of the segregation behavior of alloyed elements on the bonding strength of the interface. The computed values for W ) disclose that the segregation ability of elements from strong to weak exhibits the order of Ti > Sc > Zr > Y > Ta > Nb > Lu > Hf > Mo > V > W, while Cr and Mn elements are not easy to segregate at the interface. Sc, Ti, V, Cr, Mn, Zr, Nb, Mo, Hf, and Ta preferentially occupy Al atoms, whereas Y and Lu predominantly inhabit Mg atoms. Relative to the clean interface, the electron cloud enrichment at the interface after alloying element X (Zr, Sc, Ti, W, Hf, Mn, Y, Lu and V) doping is weakened, and the ion interaction among interface atoms is enhanced. After doping alloying element X (Nb, Mo, Ta, and Cr), the degree of electron cloud enrichment at the interface is obviously enhanced, and the covalent interaction among interface atoms is enhanced. This suggests that the introduction of alloyed elements through doping can augment the bond strength at the interface between the precipitated phase and matrix, thereby reinforcing the strength and toughness of 7xxx series alloys.ad and interfacial energies indicated that the T6S3 terminated configuration represents the interfacial structure with the highest stability across all models analyzed. Focusing on the T6S3 interface, the assessed segregated energies ( E seg ) disclose that the segregation ability of elements from strong to weak exhibits the order of Ti > Sc > Zr > Y > Ta > Nb > Lu > Hf > Mo > V > W, while Cr and Mn elements are not easy to segregate at the interface. Sc, Ti, V, Cr, Mn, Zr, Nb, Mo, Hf, and Ta preferentially occupy Al atoms, whereas Y and Lu predominantly inhabit Mg atoms. Relative to the clean interface, the electron cloud enrichment at the interface after alloying element X (Zr, Sc, Ti, W, Hf, Mn, Y, Lu and V) doping is weakened, and the ion interaction among interface atoms is enhanced. After doping alloying element X (Nb, Mo, Ta, and Cr), the degree of electron cloud enrichment at the interface is obviously enhanced, and the covalent interaction among interface atoms is enhanced. This suggests that the introduction of alloyed elements through doping can augment the bond strength at the interface between the precipitated phase and matrix, thereby reinforcing the strength and toughness of 7xxx series alloys.

π-Conjugated macrocycles have been highly attractive due to their challenging synthesis, fascinating aesthetic structure and unique physical and chemical properties. Although some progress has been made in synthesis, the study of π-macrocycles with different structural characteristics and supramolecular interactions still faces major challenges. In this paper, two new single-bond linked macrocycles (MS-4T/MS-6T) were reported, and the corresponding vinyl-bridged heterocycloarenes (MF-4T/MF-6T) were synthesized by the periphery fusion strategy. Further studies have indicated that the structure of these four macrocycles is determined by both size and curvature, showing unique variations from nearly planar to bowl and then to saddle. Interestingly, the nearly planar MS-4T with a small size and the rigid saddle-shaped MF-6T show no obvious response to fullerenes C 60 or C 70 , while the bowl-shaped MS-6T and MF-4T demonstrate a strong binding affinity towards fullerenes C 60 and C 70 . What's more, two kinds of co-crystals with capsule-like configurations, MS-6T@C 60 and MS-6T@C 70 , have been successfully obtained, among which the former shows a loose columnar arrangement while the latter displays a unique three-dimensional honeycomb arrangement that is extremely rare in supramolecular complexes. This work systematically studies the π-conjugated macrocycles and provides a new idea for the development of novel host-guest systems and further multifunctional applications., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

A cyclopenta-fused macrocyclic tetraradicaloid, MC4-S , containing alternating phenanthrene (Phen) and dibenzo[ b , d ]thiophene (DBTh) units was synthesized and isolated in single-crystal form. Compared with its all-carbon isoelectronic structure, CPTP-M , the incorporation of two sulfur atoms leads to a smaller radical character and a larger singlet-triplet energy gap. X-ray crystallographic analysis reveals that the spin-spin coupling through the DBTh unit is stronger than that through the Phen moiety. In addition, the electron-rich sulfur atoms also raise the energies of both the HOMO and LUMO in MC4-S , but the overall optical and electronic energy gaps are close to that of the CPTP-M . MC4-S displays global anti-aromaticity according to the NMR measurements and theoretical calculations (NICS, ACID and 2D ICSS), with a 36π ring current circuit along the all-carbon periphery excluding the two sulphur atoms. Its dication becomes globally aromatic due to the existence of a dominant 34π-conjugation pathway. This study sheds some light on the effect of heteroatoms on the electronic properties of open-shell polyradicaloids., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

Molecular dynamics simulations were performed to clarify the nanomechanical responses of β-Si3N4 nano-thin layers in the basal plane for indenters of various radii, different indentation velocities and at different temperatures. It was found that the maximum loading stress and indenter displacement both increase with increasing radius of the indenter. A large number of N(6h)-Si bond-breaking defects and one N(2c)-Si bond-breaking defects are responsible for the initiation of fracturing. With increasing loading velocity, the maximum loading stresses show almost no change; however, a high loading velocity can shorten the displacement of the indenter and contributes to the formation of new N(2c)-Si bond-breaking defects. Thermal fluctuations can decrease the mechanical properties of the thin layer. The maximum loading stresses and indenter displacements are sensitive to both the radius of the indenter and the loading temperature.

Self-sufficient aldehyde deformylating oxygenases (ADOs) from Synechococcus elongatus PCC7942 fused to alternative electron transfer systems were successfully designed, constructed, characterized and used for efficient conversion of aldehydes into alkanes for the first time.

The nanowire with an aspect ratio of 3 : 1 possesses a higher bending stress of 15.85 GPa. It can be observed that the initial Si-Si bond and N atom defects with a coordination number of 2, subsequently evolving to 0 and 1, with Si evolving from 5 to 6 and 7, are mainly responsible for the final fracture.

Novel organic sensitizers containing a thieno[3,4-c]pyrrole-4,6-dione (TPD) moiety with triphenylamine or julolidine as the electron donor have been designed and synthesized for quasi-solid-state dye-sensitized solar cells (DSSCs). For comparison, two organic dyes based on a terthiophene spacer have also been synthesized. The absorption, electrochemical and photovoltaic properties of all sensitizers have been systematically investigated. We found that the incorporation of TPD is highly beneficial to broaden the absorption spectra of the organic sensitizers and prevent the intermolecular interaction. Therefore, the charge recombination possibility is reduced, which is revealed by the controlled intensity modulated photovoltage spectroscopy. A quasi-solid-state DSSC based on sensitizer FNE38 with TPD and triphenylamine moieties demonstrates a solar energy conversion efficiency of 4.71% under standard AM 1.5G sunlight without the use of coadsorbant agents.

Three near infrared (NIR) metal-free organic sensitizers (FNE32, FNE34, FNE36) based on the thieno[3,4-b]pyrazine derivative have been designed and synthesized for application in quasi-solid-state dye-sensitized solar cells (DSSCs). These organic dyes demonstrate maximum absorption bands at 596-625 nm due to the presence of the thieno[3,4-b]pyrazine derivative, which facilitates the intramolecular electron transfer from the donor to the acceptor. Quasi-solid-state DSSCs based on FNE34 display efficient photoelectric conversion over the whole visible range extending into the NIR region up to 900 nm with maximum incident monochromatic photon-to-electron conversion efficiency (IPCE) of 77%, yielding a short-circuit photocurrent density of 16.24 mA cm(-2) and a power conversion efficiency of 5.30%. To the best of our knowledge, this is the highest efficiency for quasi-solid-state DSSCs based on an organic NIR dye. When exposed to one-sun illumination for 1000 h, the quasi-solid-state DSSC based on FNE34 exhibits good long-term stability with almost constant power conversion efficiency.