Aqueous solutions of disodium cromoglycate (DSCG), a representative model system for chromonic liquid crystals, exhibit temperature- and concentration-dependent phase behaviors spanning isotropic, nematic, and columnar phases, as well as their coexistence regions. [Y. Nastishin et al., J. Mol. Liq., 2018, 267, 96-99] reported that UV irradiation can alter the phase diagram, transforming a nematic phase into a nematic-isotropic biphasic state due to weakened molecular attractions, accompanied by a slow post-irradiation relaxation. Here, we revisit this phenomenon and elucidate the molecular origin of this phase diagram shift: the UV-induced photodegradation of DSCG into specific photodegradation products, which we identify using liquid chromatography-mass spectrometry. Through an integrated approach combining in situ X-ray scattering and polarized optical microscopy, we demonstrate that these degradation products disrupt the self-assembly of DSCG aggregates, thereby expanding the isotropic and biphasic regions in the phase diagram. These findings demonstrate that chromonic assemblies and their phase behaviors are highly sensitive to minor chemical alterations, providing a potential route toward light-controlled self assembly of soft matter.

Polarimetric phototransistors have attracted increasing interest due to their ability to recognize the polarization state of incident linearly polarized light. However, advances in their development have been hindered by the low polarization sensitivity that results from the modest polarization dichroic ratios (PDRs) of the photoactive materials. In this study, we present polarimetric organic phototransistors (P-OPTs) with a remarkably high polarization sensitivity exceeding 8.0. These P-OPTs are fabricated by transferring highly stretched (similar to 200%) thin films of a polymer semiconductor, poly(4-(5-(4,4-dihexadecyl-4H-cyclopenta[1,2-b:5,4-b']dithiophen-2-yl)thiophen-2-yl)-5,6-difluoro-2-octyl-7-(thiophen-2-yl)-2H-benzo[d][1,2,3]triazole) (PCDTFBTA), which exhibits a high PDR of approximately 4.0. This improved polarization sensitivity ranks among the highest sensitivities reported for polarimetric phototransistors, demonstrating high photoresponsivity (R approximate to 500 A W-1), high external quantum efficiency (EQE approximate to 1000%), high photosensitivity (P approximate to 1.8 x 10(4)), high specific detectivity (D* approximate to 5.9 x 10(12) Jones), and short rise (tau(r) approximate to 3.3 ms) and decay (tau(d) approximate to 3.4 ms) times.

This study aimed to investigate the physical and chemical properties resulting from the introduction of fluorine substituents in two copolymers, namely PBDTT-ttTPD and PFBDTT-ttTPD, which were synthesized using benzodithiophene (BDT) as donor and alkylthienothienyl thienopyrrolodione (ttTPD) as acceptor. In comparison to PBDTTttTPD, PFBDTT-ttTPD demonstrated low HOMO energy levels (-5.51 eV) and high thermal stability. Furthermore, DFT calculations provided predictions for molecular arrangement and electron distribution, which tend to be similar to experimental results, meaning these results can be used as materials for new organic semiconductors.

Albeit considerable attention to the fast-developing organic thermoelectric (OTE) materials due to their flexibility and non-toxic features, it is still challenging to design an OTE polymer with superior thermoelectric properties. In this work, two "isomorphic" donor-acceptor (D-A) conjugated polymers are studied as the semiconductor in OTE devices, revealing for the first time the internal mechanism of regioregularity on thermoelectric performances in D-A type polymers. A higher molecular structure regularity can lead to higher crystalline order and mobility, higher doping efficiency, order of energy state, and thermoelectric (TE) performance. As a result, the regioregular P2F exhibits a maximum power factor (PF) of up to 113.27 µW m-1  K-2 , more than three times that of the regiorandom PRF (35.35 µW m-1  K-2 ). However, the regular backbone also implies lower miscibility with a dopant, negatively affecting TE performance. Therefore, the trade-off between doping efficiency and miscibility plays a vital role in OTE materials, and this work sheds light on the molecular design strategy of OTE polymers with state-of-the-art performances.

AbstractDespite the emerging scientific interest in polymer‐based stretchable electronics, the trade‐off between the crystallinity and stretchability of intrinsically stretchable polymer semiconductors—charge‐carrier mobility increases as crystallinity increases while stretchability decreases—hinders the development of high‐performance stretchable electronics. Herein, a highly stretchable polymer semiconductor is reported that shows concurrently improved thin film crystallinity and stretchability upon thermal annealing. The polymer thin films annealed at temperatures higher than their crystallization temperatures exhibit substantially improved thin film stretchability (> 200%) and hole mobility (≥ 0.2 cm2 V−1 s−1). The simultaneous enhancement of the crystallinity and stretchability is attributed to the thermally‐assisted structural phase transition that allows the formation of edge‐on crystallites and reinforces interchain noncovalent interactions. These results provide new insights into how the current crystallinity–stretchability limitation can be overcome. Furthermore, the results will facilitate the design of high‐mobility stretchable polymer semiconductors for high‐performance stretchable electronics.

Weexplore the potential of employing diketopyrrolopyrrole (DPP)based pi-conjugated OSs as a hole transport layer material inheteroatom-doped hematite (Ti-Fe2O3/Ge-Fe2O3) photoanodes for efficient photoelectrochemicalwater splitting. The siloxane-modified pi-conjugated polymer(P-Si) with a high carrier mobility and crystallinity revealedgreat potential to extract holes by forming a built-in potential withhematite photoanodes while showing high stability in an alkaline electrolytefor photoelectrochemical water oxidation. Because of the easy holeextraction and subsequent fast hole transport property of the P-Si interlayer between NiFe-(OH)( x ) and Ge-doped porous Fe2O3(Ge-PH), NiFe-(OH)( x )/P-Si/Ge-PH showed a 1.8-fold increasein photocurrent density (4.57 mA cm(-2) at 1.23 V-RHE) with a cathodic shift of the onset potential (0.735 V-RHE) and good stability for 65 h compared to Ge-PH. This studydemonstrates the successful use of inherently unstable pi-conjugatedOSs as a hole extracting/transport medium in a photoanode, addressingthe intrinsic recombination issues of hematite for efficient and stablewater splitting.

Organic electrochemical transistors (OECTs) have enormous potential for use in biosignal amplifiers, analyte sensors, and neuromorphic electronics owing to their exceptionally large transconductance. However, it is challenging to simultaneously achieve high charge carrier mobility and volumetric capacitance, the two most important figures of merit in OECTs. Herein, a method of achieving high-performance OECT with donor-acceptor conjugated copolymers by introducing fluorine units is proposed. A series of cyclopentadithiophene-benzothiadiazole (CDT-BT) copolymers for use in high-performance OECTs with enhanced charge carrier mobility (from 0.65 to 1.73 cm2·V-1·s-1) and extended volumetric capacitance (from 44.8 to 57.6 F·cm-3) by fluorine substitution is achieved. The increase in the volumetric capacitance of the fluorinated polymers is attributed to either an increase in the volume at which ions can enter the film or a decrease in the effective distance between the ions and polymer backbones. The fluorine substitution increases the backbone planarity of the CDT-BT copolymers, enabling more efficient charge carrier transport. The fluorination strategy of this work suggests the more versatile use of conjugated polymers for high-performance OECTs.

D-D-A-A type conjugated polymers with both cyclopentadithiopene and prydylthiadiazole, poly(4-(4,4,4',4'tetrahexadecyl-4H,4'H-[2,2'-bi(cyclopenta[1,2-b:5,4-b']dithiophen)]-6-yl)-7,7'-bi[1,2,5]thiadiazolo[3,4-c]pyridine) (P1) and poly((E)-4-(6-(2-(4,4-dihexadecyl-4H-cyclopenta[1,2-b:5,4-b']dithiophen-2-yl)vinyl)-4,4-dihexadecyl-4H-cyclopenta[1,2-b:5,4-b']dithiophen-2-yl)-7,7'-bi[1,2,5]thiadiazolo[3,4-c]pyridine) (P2) were synthesized. To investigate optoelectro properties and theorical study, UV-visible spectroscopy, cyclic voltammetry, and density functional theory were carried out.

Replacing inorganic semiconductors with organic semiconductors for photoelectrochemical water-splitting (PEC-WS) has been challenging. In this study, a photoanode was fabricated by both n-type organic semiconductor, poly{[N,N'-bis(2-octyldodecyl)naphthalene-1,4,5,8-bis(dicarboximide)-2,6-diyl]-alt-5,5'-(2,2'-bithiophene)} (N2200) and a newly synthesized conjugated polymer, poly(4-(4,4-dihexadecyl-4H-cyclopenta[1,2-b:5,4-b']dithiophen-2-yl)-7-(4,4as an additive and it has enhanced photocurrent density. Linear sweep voltammetry revealed that the addition of PCFCS (5.0 ??g) increased the photocurrent density up to 62.5% (1.12 to 1.82 ??A/cm2). toanode.

The effect of incorporating chalcogenophene comonomers, namely, furan, thiophene, and selenophene, on the optoelectrical properties of cyclopentadithiophene-based polymers (P1, P2, and P3, respectively) for organic field-effect transistors is reported. The optical, electrical, and morphological properties of the P1, P2, and P3 are investigated. Compared to the other polymers, the P2 showed the highest crystallinity with the shortest pi-pi stacking distance (d pi-pi approximate to 3.58 angstrom) and the longest crystalline length (Lc approximate to 40 angstrom), as confirmed by two-dimensional grazing incidence wide-angle X-ray diffraction. However, P3 had the highest hole mobility (mu = 0.25 cm2/V-s), which is higher than P1 (mu = 0.06 cm2/V-s) and P2 (mu = 0.20 cm2/V-s). The relatively lower mobility of the P2 compared to that of the P3 is attributed to its island-like crystalline domains, confirmed by atomic force mi-croscopy results and the lower edge-on crystallite ratio. Our findings suggest a new design guideline for developing high-mobility pi-conjugated polymers.

A redox-active mixed ion and electron conductor (redox-active MIEC) is presented as a binder. High capacity was guaranteed, particularly at high rates due to its MIEC nature, while an additional capacity was achieved from its redox activity.

Because of the limited availability of synthetic strategies and strong acceptor units, constructing new types of low-band-gap donor-acceptor-type copolymers for use in multiple functional applications remains a big challenge. Herein, we report the synthesis, characterization, and optoelectronic applications (i.e., organic field-effect transistors (OFETs) and organic phototransistors (OPTs)) of a novel class of ultralow-band-gap copolymers (PDAP-Fu, PDAP-Th, and PDAP-Se) on the basis of the unique, interesting, yet rarely researched bicyclic 2,5-diazapentalene (DAP) strong acceptor in conjugation with chalcogenophene donors (furan (Fu), thiophene (Th), or selenophene (Se)). All of the copolymers exhibit broad near-infrared (NIR) absorption and optical band gaps as low as similar to 1.0 eV. The effects of the actual chalcogen atoms on the geometry, optical properties, energy levels, and film organization are carefully determined for OFET and OPT applications. Regarding the OFET studies, all of the copolymers show unipolar transport behavior in bottom-gate and top-contact OFETs, and PDAP-Se exhibits the highest hole mobility of 4.76 x 10(-1) cm(2) V-1 s(-1). Besides, investigations of the OPTs indicate that a high photoresponse is achieved for all of the copolymers at a wavelength of 1060 nm in the NIR spectral region combined with an excellent external quantum efficiency (eta) and photodetectivity (D*). This is particularly true for PDAP-Se (eta = 6.56 x 10(4)% and D* = 1.80 x 10(12) Jones). Thus, such ultralow-band-gap copolymers are promising candidates for use in integrated circuits and optoelectronic devices.

Apart from power conversion efficiency (PCE) being the most important feature that requires improvement for organic solar cells (OSCs), their long‐term stability is another key factor for their successful commercialization. In fact, the lifetime of OSCs is severely limited by photoinduced oxidation, which occurs because of light radiation and the ingress of moisture (H 2 O) and oxygen (O 2 ) within an ambient atmosphere. Herein, dibutylhydroxytoluene (BHT)‐based nonvolatile antioxidant additives with polar cyanide (CN) and perfluorinated alkyl chains (designated as BHT–CN and BHT–PF) are developed, demonstrating that the OSCs will have significantly improved long‐term stability by using them when exposed to the combined action of all the aforementioned stresses. In particular, the use of BHT–PF in the various given test‐bed OSC systems can remarkably enhance the long‐term stability, as well as the high initial PCEs similar to the maximized values obtained from the highly optimized OSCs with each well‐known suitable solvent additive. The promising results are attributed to the simultaneously enhanced dielectric and radical scavenging properties induced by the BHT–PF embedded in the active‐layer matrices. Taking its easy applicability into consideration, the BHT–PF is very useful in fabricating OSC modules that should be stable under severe photo‐oxidation conditions.

Spontaneously spreading (SS) film process with water substrates in the air (inert free atmosphere) has recently emerged as an effective technique for the fabrication of large-area organic solar cells (OSCs), however, there are limited studies on the process until now. Herein, we carried out an in-depth study on the influence of varying the temperature of the water substrate during the SS process on the quality of the film and performance of two testbed OSC devices (PM6:ITIC-4F and PM6:Y7). By accounting for the changes in the kinetics and thermodynamics of the evaporation and dissolution of the solvent in water, we observed a striking water temperature dependence of the morphology and OSC performance. Via careful device optimization with the varying water temperatures, we achieved high power conversion efficiencies (PCEs) of 11.13% and 13.83% for PM6:ITIC-4F-and PM6:Y7based SS-OSCs processed at 25 degrees C water temperature, respectively. The 13.83% PCE is the hitherto the highest reported value of the air-processed SS-OSCs. The strategy reported herein with which the quality of films can be controlled by simple modulation of the water temperature can promote the utilization of the SS process in the fabrication of scalable devices of various organic semiconductors.

A family of the SM-axis series based on benzo[1,​2-​b:4,​5-​b']​dithiophene and 3-ethylrhodanine (RD) units with structurally different π-conjugation systems are synthesized as a means to understand the structure-property relationship of conjugated pathways in ternary non-fullerene organic solar cells (NF-OSCs) as a third component. The optical and electrochemical properties of the SM-axis are highly sensitive both to the functionalized direction and to the number of RD groups. Enhanced power conversion efficiencies (PCEs) of over 11% in ternary devices are obtained by incorporating optimal SM-X and SM-Y contents from PBDB-T:ITIC binary NF-OSCs, while a slightly lower PCE is observed with the addition of SM-XY. The results of in-depth studies using various characterization techniques demonstrate that working mechanisms of SM-axis-based ternary NF-OSCs are distinctly different from one another: an energy-transfer mechanism with an alloy-like model for SM-X, a charge transfer with the same model for SM-Y, and an energy transfer without such a structure for SM-XY. As extension of the scope, a SM-X-based ternary NF-OSC in the PM6:IT4F system also shows a greatly enhanced PCE of over 13%. The findings provide insights into the effects of conjugated pathways of organic semiconductors on mechanisms of ternary NF-OSCs, advancing the understanding for synthetic chemists, materials engineers, and device physicists.

The emergence of fluorescent graphene quantum dots (GQDs) is expected to enhance the usefulness of quantum dots (QDs), in terms of their unique luminescence, photostability, low toxicity, chemical resistance, and electron transport properties. Here we prepared blue-photoluminescent polyethylene glycol GQDs (PEG-GQDs) through PEG surface passivation. The photoluminescence (PL) quantum yield (QY) of PEG-GQDs with 320 nm excitation was about 4.9%, which was higher than that of pure GQDs. The as-fabricated PEG-GQDs with high QY were then used as light-emitting diode (PGQD-LED) emitters, in which the GQDs were incorporated into polymeric host layers in a multilayer electroluminescent device; blue emission with a luminance exceeding 800 cd m-2 was achieved, thus demonstrating the potential of PEG-GQDs as emitters in electroluminescence applications. Furthermore, the fluorescence mechanism of PEG-GQDs was investigated and proved that the origin of strong fluorescence of PEG-GQDs is associated with the luminescence from intrinsic states. The highly fluorescent PEG-GQDs will allow new devices, such as multicolor LEDs, to be developed with extraordinary properties, by tailoring the intrinsic and extrinsic states.

Two solid additives, BDT-1 and BDT-2, in non-fullerene polymer solar cells enhance photovoltaic efficiencies up to 16.26% with improved thermal and photoinduced stabilities.

In principle, an electric field via ferroelectric materials can affect the photovoltaic properties, although there is not yet a complete mechanistic understanding. Herein, a built-in electric field without a poling processing step was established by introducing developed PVDF-based ferroelectric additives within active-layer matrices of organic solar cells (OSCs). Upon the existence of the ferroelectric polarization induced by the ferroelectric additives in o-xylene/N-methylpyrrolidone pair featuring halogen-free processing system, high efficiencies of 11.02% and 11.76% are achieved in fullerene and non-fullerene acceptor bulk-heterojunction OSCs, respectively. A comparative study exploring the role of the ferroelectric polarization surrounding the active-layer matrix was also performed using structural, electrical, and morphological techniques, to shed light on the underlying ferroelectric polarization effects on OSCs. Furthermore, the use of the ferroelectric additive is extended to p-n like bilayer OSC to access a rich understanding of the complex enhancement mechanisms afforded by it, demonstrating a highly efficient (11.83%) bilayer device. The above results are fairly comparable to the highest value reported for the recently developed state-of-the-art OSCs processed from halogen-free systems. The use of the ferroelectric additives in the halogen-free system is promising in related organic-semiconductor fields for reasons extending beyond the enhancement of efficiency and the environment-friendly manufacturing.

The performance of organic solar cells (OSCs) has been steadily increasing, surpassing 16% power conversion efficiency (PCE) with advances in photoactive and charge transport materials. Nonetheless, the performance of flexible OSCs still falls behind that of their rigid counterparts. Furthermore, commonly used plastic substrates are vulnerable to high-temperature annealing processes. Herein, a highly flexible and durable electrode with thermal stability achieved through direct integration of polyimide (PI) on graphene is introduced. The PI-assisted graphene electrode exhibits an ultra-clean surface together with an optical transmittance exceeding 92%, a sheet resistance of 83 U/sq, and thermal stability. Moreover, direct integration of PI improved the durability of the graphene electrode by inhibiting delamination of the graphene under mechanical stress. Using the PI- assisted graphene electrode, flexible OSC with a PCE of 15.2% was obtained with outstanding mechanical robustness. The proposed electrode is promising for use in various optoelectronic devices requiring high efficiency and flexibility.

It is extremely important to develop nontoxic solvent and additive-processed high-performance all-polymer solar cells (all-PSCs) that are suitable for printing preparation of large-scale devices. Herein, it is demonstrates that a simple random copolymerization of two acceptor monomers (benzo[1,2-c:4,5-c ']dithiophene-4,8-dione (BDD) and 5,6-difluoro-2H-benzo[d][1,2,3]triazole (FTAZ)), alternating with Si atom-containing benzo[1,2-b:4,5-b ']dithiophene donor comonomer, forms a successful approach by which to synthesize donor copolymers with excellent solubility/processability for nontoxic-solvent-processed all-PSCs. The incorporation of a higher degree of BDD in the backbone lowers the frontier energy levels, as well as redshifts, with higher absorption coefficients; however, it adversely affects solubility in a 2-methyltetrahydrofuran (MeTHF). An impressive power conversion efficiency, of about 8.0%, is achieved from PJ25 (25 mol% BDD)-based all-PSC when paired with N2200-F30 acceptor random copolymer by using MeTHF as the processing solvent without any additive. Another interesting point is that the air stability of the all-PSCs increases with increasing FTAZ content due to strong noncovalent interaction and resistance to humidity and oxidation caused by the F-atoms in FTAZ units. Not only does this study establish a structure-property-performance relationship through a series of structural, morphological, and electrical characterization techniques, but it also provides a promising and easy way to develop nontoxic-solvent-processed high-performance all-PSCs.