Search

The simple chalcogen atom substitution of quinoidal molecules and polymers induces the significant alternation of various properties as well as molecular geometries.

In this work, we synthesized and characterized two quinoidal small molecules based on benzothiophene modified and original isatin terminal units, benzothiophene quinoidal thiophene (BzTQuT) and quinoidal thiophene (QuT), respectively, to investigate the effect of introducing a fused ring into the termini of quinoidal molecules. Extending the terminal unit of the quinoidal molecule affected the extension of π-electron delocalization and decreased the bond length alternation, which led to the downshifting of the collective Raman band and dramatically lowering the band gap. Organic field-effect transistor (OFET) devices in neat BzTQuT films showed p-type transport behavior with low hole mobility, which was ascribed to the unsuitable film morphology for charge transport. By blending with an amorphous insulating polymer, polystyrene, and poly(2-vinylnaphthalene), an OFET based on a BzTQuT film annealed at 150 °C exhibited improved mobility up to 0.09 cm2 V–1 s–1. This work successfully demonstrated that the extension of terminal groups into the quinoidal structure should be an effective strategy for constructing narrow band gap and high charge transporting organic semiconductors.

Direct arylation polymerization (DArP) is a synthetic method for conjugated polymers; in DArP, organometallic functionalization steps are omitted and there are no toxic byproducts. As a result, it is considered a more sustainable alternative compared to conventional methods such as Stille polymerization. To explore the possibility of DArP-based polymers as donor materials in organic solar cells (OSCs), a series of conjugated polymers based on the structure of PDCBT (poly[2,2''''-bis[[(2-butyloctyl)oxy]carbonyl][2,2':5',2'':5'',2'''-quaterthiophene]-5,5'''-diyl]) are synthesized using DArP and Stille polymerization. By controlling the monomer concentration and reaction time in DArP, DArP-5 with the highest M

To enable the application of semiconducting single-walled carbon nanotubes (sc-SWNTs) in advanced technologies, the SWNT chiralities must be sorted from the mixture of as-synthesized SWNTs. Interes...

While quinoidal moieties are considered as emerging platforms showing efficient charge transport and interesting open-shell diradical characteristics, whether these properties could be changed by extension to the conjugated polymer structure remains as a fundamental question. Here, we developed and characterized two conjugated polymers incorporating quinoids with different lengths, which have a stable close- and open-shell diradical character, respectively, namely, poly(quinoidal thiophene-thienylene vinylene) (PQuT-TV) and poly(quinoidal bithiophene-thienylene vinylene) (PQuBT-TV). A longer length of a quinoidal core led to enhanced diradical characteristics. Therefore, the longer core length of QuBT was favorable for the formation of an open-shell diradical structure in its monomer and in the quinoidal polymer. PQuBT-TV exhibited high spin characteristics observed by the strong ESR signal, a low band gap, and improved electrochemical stability. On the other hand, as QuT maintained a closed-shell quinoid structure, PQuT-TV exhibited high backbone coplanarity and strong intermolecular interaction, which was beneficial for charge transport and led to high hole mobility (up to 2.40 cm2 V-1 s-1) in organic field-effect transistors. This work successfully demonstrated how the control of the closed/open-shell character of quinoidal building blocks changes charge transport and spin properties of quinoidal conjugated polymers via quinoid-aromatic interconversion.

Since quinoidal molecules have double-bond linkages between aromatic rings, they have many advantages for efficient charge transport resulting from high planarity and extended π-conjugation length. However, they unavoidably generate some isomers, which cause difficulty in purification and characterization. In this study, sulfur–oxygen conformation locking and steric repulsion approach is introduced to manipulate syn- and anti-isomerization of a quinoidal building block (bis-QEDOT). As a result, isomer-free bis-QEDOT is synthesized by introducing the 3,4-ethylenedioxy group, and the geometrical structure of bis-QEDOT is identified by thin-layer chromatography, 1H NMR, and density functional theory calculation. Furthermore, thiophene (T), bithiophene (2T), and thienylene vinylene (TV) as π-conjugated building blocks are polymerized with bis-QEDOT. Due to the quinoid structure, PQEDOT-T, PQEDOT-2T, and PQEDOT-TV show an intensified near-IR absorption and a low band gap around ∼1.16 eV. Grazing incidence wide-angle X-ray diffraction reveals that three quinoidal polymers show in the (h00) diffraction peaks up to third order after thermal annealing at 250 °C, demonstrating high crystallinity of the films. Finally, the electrical properties of the three polymers are investigated as an active layer in organic field-effect transistors showing hole mobilities of 4.3 × 10–2 (PQEDOT-T), 1.8 × 10–2 (PQEDOT-2T), and 7.8 × 10–3 cm2 V–1 s–1 (PQEDOT-TV).

As a coating method compatible with printing, one-step spin-coating is widely used for fabricating perovskite thin films. Controlling the crystal growth rate of two precursors is essential to obtain a homogeneous film morphology. However, the film formation mechanism and role of solvate systems during spin-coating have not yet been clearly revealed. In this work, we implemented the in situ grazing incidence wide-angle X-ray scattering of CH3NH3PbI3 perovskite material based on various additive systems to adjust the unbalanced crystal growth rate of CH3NH3I and PbI2. As we expected, the behavior of the solvate phase was strikingly mediated by various additives, and one of the additives greatly slowed the PbI2 solvate phase, thus overcoming the imbalance in the crystal growth rate. Consequently, the well-controlled perovskite films have both good film morphology and high photovoltaic performance with excellent reproducibility.

Despite significant progress in organic photovoltaics (OPVs), efforts to fabricate the small-molecule OPVs by scalable printing methods have hardly been devoted. Herein, we demonstrate large-area p...

In this study, we obtained a new structural insight into the charge-transporting properties in TPD-based polymers that cannot be solely explained in terms of the type of orientation. We synthesized...

The chlorinated isoindigo (CI) is a promising building block for organic semiconducting materials because the favorable properties, such as ready availability, lower price, and higher capability to hold the electron density than fluorine atoms, make them advantageous for use in semiconducting materials. It was reported that CI can be more readily synthesized than fluorinated isoindigo (FI), and the CI-based conjugated polymer exhibited comparable device performance with the FI-based conjugated polymer. Chorine-substituted conjugated molecules, however, have been less investigated than that of the fluorine atom, presumably, due to the large size of the chlorine atom, which induces steric hindrance effects in the conjugated backbone. In this study, we systematically investigate the effect of the structural property, flexibility vs rigidity, of the donor unit on the crystallinity and charge transport characteristics of chlorinated isoindigo acceptor-based D-A-type conjugated polymers to understanding the str...

Creating an orthogonal printable hole-transporting layer (HTL) without damaging the underlying layer is still a major challenge in fabricating large-area printed inverted polymer solar cells (PSCs). In this study, we prepared orthogonal-processable fluorine-functionalized reduced graphene oxide (FrGO) series with various two-dimensional sheet sizes such as large-sized FrGO (1.1 μm), medium-sized FrGO (0.7 μm), and small-sized FrGO (0.3 μm) and systematically investigated the size effect of FrGOs on the hole transport properties of PSCs. The FrGOs exhibit highly stable dispersion without change over 90 days in 2-propanol solvent, indicating very high dispersion stability. Decreasing the sheet size of FrGOs enhanced hole-transporting properties, resulting in power conversion efficiencies (PCEs) of 9.27 and 9.02% for PTB7-Th:EH-IDTBR- and PTB7-Th:PC

The morphology of conjugated polymer thin films, determined by the kinetics of film drying, is closely correlated with their electrical properties. Herein, we focused on dramatic changes in the thin-film morphology of blade-coated poly­{[N,N′-bis­(2-octyldodecyl)-naphthalene-1,4,5,8-bis­(dicarboximide)-2,6-diyl]-alt-5,5′-(2,2′-bithiophene)} caused by the effect of solvent and coating temperature. Through in situ measurements, the evolution of polymer aggregates and crystallites, which plays a decisive role in the formation of the charge-transport pathway, was observed in real time. By combining in situ ultraviolet–visible spectroscopy and in situ grazing-incidence wide-angle X-ray scattering analysis, we could identify five distinct stages during the blade-coating process; these stages were observed irrespective of the solvent and coating temperature used. The five stages are described in detail with a proposed model of film formation. This insight is an important step in understanding the relationship between the morphology of thin polymer films and their charge-transport properties as well as in optimizing the structural evolution of thin films.

Murine models have become powerful tools in leukemia research for investigating interactions between blast cells niche factors. In the tumor microenvironment, immune cells are one of the most important niche factors, capable of mounting dynamic innate or adoptive responses against leukemic cells. Acute myeloid leukemia (AML) is a systemic cancer accompanied by immune disruption. In order to exploit the enhanced activity of immune cells in AML treatment, the use of syngeneic mouse models is necessary. Studies of crosstalk between cancer blast cells and immune cells in syngeneic mouse models are beneficial, as the absence of immune functions in syngeneic models enables focus on cancer-associated immune reactions. Once AML is induced, innate and adoptive immune cells respond differently, ultimately resulting in suppression of the immune cells. Murine AML models are commonly induced by intravenous or subcutaneous injection of C1498 cells. Despite the popularity of murine models, they have not yet resulted in the elucidation of distinct differences in immune cells by the injection method. Here, we investigated the frequency of immune cells and survival rate of mice with AML induced using both injection methods.

Murine models have become powerful tools in leukemia research for investigating interactions between blast cells niche factors. In the tumor microenvironment, immune cells are one of the most important niche factors, capable of mounting dynamic innate or adoptive responses against leukemic cells. Acute myeloid leukemia (AML) is a systemic cancer accompanied by immune disruption. In order to exploit the enhanced activity of immune cells in AML treatment, the use of syngeneic mouse models is necessary. Studies of crosstalk between cancer blast cells and immune cells in syngeneic mouse models are beneficial, as the absence of immune functions in syngeneic models enables focus on cancer-associated immune reactions. Once AML is induced, innate and adoptive immune cells respond differently, ultimately resulting in suppression of the immune cells. Murine AML models are commonly induced by intravenous or subcutaneous injection of C1498 cells. Despite the popularity of murine models, they have not yet resulted in the elucidation of distinct differences in immune cells by the injection method. Here, we investigated the frequency of immune cells and survival rate of mice with AML induced using both injection methods.

We report on controllable ambipolar charge transport in polymeric semiconductors by the incorporation of viologen-based molecular additives. The viologen dopants selectively contribute to an increase in the charge carrier density of the electrons while enhancing the fibril-like crystalline thin-film morphology of the polymers to provide favourable charge transport in staggered-structure organic field-effect transistors. A well-balanced ambipolar behaviour is obtained at the optimised viologen concentration in donor-acceptor conjugated polymers by conversely modulating the p- and n-channel carrier mobilities within a given active layer. Complementary-like inverter circuits are demonstrated through the application of a simple blanket coating of a viologen-doped ambipolar semiconductor, which exhibits high ideal voltage switching at around half of the applied bias, a high gain of more than 50, and sufficient noise immunity to enable various applications for printed electronics and optoelectronics.

A solution-processable hole transporting layer (HTL) is developed using in situ formation of 2D vanadyl phosphate (VP) layered on 2D reduced graphene nanosheet (VP-rGO) for high-efficiency organic solar cells (OSCs). For the reduction of graphene oxide (GO), irradiation with electron beam was used, and for the exfoliation of VP and the blend of VP and rGO, the sonication was used. To investigate the feasibility of VP-rGO, produced by simple method for mass production, as a HTL, the surface, chemical element and electrical properties were carried out and we fabricated organic solar cells (OSCs) based on PTB7-th:PC71BM with VP-rGO as a HTL. The 2D/2D VP-rGO hybrid material specially takes advantage of both high work function of VP and good conductivity of rGO. This result leads to considerable improvement of performance in OSCs based on VP-rGO, compared with OSCs based on the PEDOT:PSS.

Expandability of organic electronics has stimulated ongoing research for the development of a variety of flexible and/or large-area optoelectronic applications. Among these electronic devices, organic non-volatile memories are emerging as suitable components for solid-state data storage because of their low-cost fabrication, large storage capacity, light weight, and conformable mechanical properties. To fully integrate organic memories with wearable and flexible/stretchable electronic systems, it is important to develop a device in which the properties such as threshold voltage and operating regime are controllable. This leads to improvement in the adaptability of the device to peripheral circuitry and encourages the development of multi-functional organic electronic components. Here, we investigate the tunable electrical properties of charge-trap (electret) memory devices based on organic field-effect transistors, obtained by the doping of an ambipolar polymer semiconductor. The electret memory devices using the doped semiconductor showed a remarkable enhancement in the charge-storage capacity, an excellent charge retention time of more than 107 s, and four-fold increase in charge carrier mobility. The improved memory characteristics associated with the controllable molecular doping could pave the way for the development of next-generation memory devices that are compatible with flexible and printed electronic technology.

CH3NH3PbI3-based planar perovskite solar cells were fabricated by slot-die coating, a scalable method. Slot-die coating tends to produce perovskite layers with much lower coverage with overgrown crystals than spin coating, which does not include a self-drying mechanism in the process. To mimic the self-drying behavior inherent in spin coating, the present study introduces a blowing step in the slot-die coating method, which significantly improved coverage of the prepared slot-die coated perovskite films. The slot-die-coated device with blowing showed a moderate power conversion efficiency (PCE) of 8.8%. The morphology of the slot-die-coated perovskite film is further improved by optimizing the deposition temperature. The combination of blowing and heating during the slot-die-coating step and the introduction of a printing-friendly hole transport layer resulted in a PCE of 12.7% for the devices fabricated in air.

Recently, many kinds of printing processes have been studied to fabricate perovskite solar cells (PeSCs) for mass production. Among them, slot-die coating is a promising candidate for roll-to-roll processing because of high-throughput, easy module patterning, and a premetered coating system. In this work, we employed mixed lead precursors consisting of PbAc2 and PbCl2 to fabricate PeSCs via slot-die coating. We observed that slot-die-coated perovskite films based on the mixed lead precursors exhibited well-grown and uniform morphology, which was hard to achieve by using only a single lead source. Consequently, PeSCs made with this precursor system showed improved device performance and reproducibility over single PbAc2. Lastly, a large-area module with an active area of 10 cm2 was fabricated with a power conversion efficiency of 8.3%.

Controlling the morphology of conjugated polymer film through careful selection of solvent is very important for facilitating charge transport in organic opto-electrical and electrical devices. In this report, we systematically study on a selection rule for optimum solvent choice to achieve highly aligned conjugated polymer chains with large ordered domain sizes for high performance organic field-effect transistors (OFETs) through various experimental analysis and Hansen solubility parameters. Three parameters: boiling point, solubility, and molecular interaction between conjugated polymer and solvents, are the most important to obtain optimum morphology. Similar molecular interaction values between solvent and conjugated polymer determined the formation of larger size ordered domain in films. High boiling point and relatively poor solubility solvents affect anisotropic film formation of conjugated polymer chains during off-center spin-coating. Considering these, large ordered domains with highly aligned diketopyrrolopyrrole thieno[3,2-b]thiophene (DPPT-TT) polymer chains were achieved by these important factors, and we demonstrate impressively high field-effect mobility ∼5.89 cm2 V−1 s−1 with low standard deviation (13%), which is the highest reported value so far for top-gate/bottom-contact DPPT-TT OFETs.

The demand for high-purity semiconducting single-walled carbon nanotubes (sc-SWNTs) has increased considerably with the aim of utilizing their superior properties in a range of future applications. Among post-sorting methods, conjugated polymers have been regarded as one of the candidates to selectively isolate sc-SWNTs with uniform electrical properties. Herein, we demonstrate the ability to selectively sort two types of SWNTs by the two polymers PCTV18T and PC12TV18T, which have different alkyl side-chain densities. PC12TV18T, with a high alkyl chain density, shows great sorting ability for both high-pressure carbon monoxide and plasma-torch-grown SWNTs with a weight ratio of almost 1:1 in toluene solution. In addition, it is found that PC12TV18T selectively sorts sc-SWNTs with the high purity. The chirality and diameters of the enriched sc-SWNTs are further confirmed by Raman spectroscopy and photoluminescence excitation/emission mapping. Finally, we fabricate bottom gate/bottom contact thin-film transistors using the enriched sc-SWNTs as semiconductors to verify the electrical performance. Devices with well-percolated sc-SWNT networks displayed p -dominant properties with average charge-carrier mobilities of 2.05 cm 2 V −1 S −1 and 9.87 cm 2 V −1 S −1 and on/off current ratios of approximately 10 4 and 10 5 for high-pressure carbon monoxide and plasma-torch-grown SWNTs, respectively.

A nanostructured micro-prism array (MPA) was integrated onto a solar module consisting of multiple perovskite solar cells (PeSCs) to minimize optical losses from surface reflection and the inactive areas reserved for interconnection. The MPA structure redirects light that is incident on inactive areas onto active sub-cell areas to improve the light harvesting efficiency. The nanoscale sub-wavelength structures (SWSs) minimize the surface reflection at the surface of the PeSC module. Combining the technical advantages of these two structures, the MPA decorated with nanoscale SWSs improves the performance of the PeSC module. The short circuit current of the PeSC module employing the MPA decorated with nanoscale SWSs was improved by 1.4 mA/cm2 compared to a conventional PeSC module covered with bare glass.

For the first time, the photovoltaic modules composed of small molecule were successfully fabricated by using roll-to-roll compatible printing techniques. In this study, blend films of small molecules, BTR and PC71BM were slot-die coated using a halogen-free solvent system. As a result, high efficiencies of 7.46% and 6.56% were achieved from time-consuming solvent vapor annealing (SVA) treatment and roll-to-roll compatible solvent additive approaches, respectively. After successful verification of our roll-to-roll compatible method on small-area devices, we further fabricated large-area photovoltaic modules with a total active area of 10 cm2, achieving a power conversion efficiency (PCE) of 4.83%. This demonstration of large-area photovoltaic modules through roll-to-roll compatible printing methods, even based on a halogen-free solvent, suggests the great potential for the industrial-scale production of organic solar cells (OSCs).

Fluorine (F) substitution on conjugated polymers in polymer solar cells (PSCs) has a diverse effect on molecular properties and device performance. We present a series of three D-A type conjugated polymers (PBT, PFBT, and PDFBT) based on dithienothiophene and benzothiadiazole units with different numbers of F atoms to explain the influence of F substitution by comparing the molecular interactions of the polymers and the recombination kinetics in PSCs. The preaggregation behavior of PFBT and PDFBT in o-DCB at the UV–vis absorption spectra proves that both polymers have strong intermolecular interactions. Besides, more closely packed structures and change into face-on orientation of fluorinated polymers are observed in polymer:PC71BM blends by GIXD which is beneficial for charge transport and, ultimately, for current density in PSCs (4.3, 13.0, and 14.5 mA cm–2 for PBT, PFBT, and PDFBT, respectively). Also, the introduction of F atoms on conjugated backbones affects the recombination kinetics by suppressing...

Solution-processed thin film transistors can be implemented using simple and low cost fabrication, and are the best candidates for commercialization due to their application to a range of wearable electronics. We report an ambipolar charge injection interlayer that can improve both hole and electron injection in organic field-effect transistors (OFETs) with inexpensive source-drain electrodes. The solution processed ambipolar injection layer is fabricated by selective dispersion of semiconducting single walled carbon nanotubes using poly(9,9-dioctylfluorene). OFETs with molybdenum (Mo) contacts and interlayer (Mo/interlayer OFETs) exhibit superior performance, including higher hole and electron mobilities, device yield, lower threshold voltages, and lower trap densities than those of bare transistors. While OFETs with Mo contacts show unipolar p-type behaviour, Mo/interlayer OFETs display ambipolar transport due to significant enhancement of electron injection. In the p-type region, transistor performance is comparable to devices with gold (Au). Hole mobility is increased approximately ten-fold over devices with only Mo contacts. The electron mobility of Mo/interlayer OFETs is 0.05 cm2V−1s−1, which is higher than devices with Au electrodes. The p-type contact resistances of Mo/interlayer OFETs are half those of OFETs with Mo contacts. Trap density in Mo/interlayer OFETs is one order magnitude lower than that of pristine devices. We also demonstrate that this approach is extendible to other metals (nickel) and n-type semiconductors with different energy levels. Injection by tunnelling is suggested as the mechanism of ambipolar injection.

A series of D-A type conjugated polymers based on (E)-1,2-bis(3-dodecyllthiophen-2-yl)ethene (TV) as electron donor unit and with different repeating subunits, PTVBO8 , PTVBT8 , PTVTBO12 , and PTVTBT12 were synthesized for use in organic field effect transistors and bulk heterojunction organic photovoltaics. Upon incorporation of alkoxy substituents in acceptor units, benzooxadiazole (BO) and benzothiadiazole (BT), polymer solubility improved and higher molecular weight polymers were obtained. In addition, all copolymers showed favorable thermal stability (T d > 300 °C), and low band gap properties (1.49–1.67 eV). The thiophene-flanked TV-TBX copolymers, PTVTBO12 and PTVTBT12, exhibited higher molecular weight and superior device performance in both OFETs and OPVs compared with the TV-BX copolymers. The electronic energy levels of copolymers were strongly influenced by the nature of acceptor units, while optical band gaps and shape of molecular orientation of polymer chains were affected by the presence or absence of thiophene spacer. Charge carrier mobilities in TV-TBX copolymers were 1 order of magnitude greater than in TV-BX copolymers. OFETs based on a PTVTBT12 with TG/BC configuration displayed the highest hole mobility of 0.48 cm 2 V −1 s −1 . The photovoltaic device containing a PTVTBO12 :PC 71 BM (1:2 w/w) blend system exhibited best performance with a V oc of 0.56 V, a short-circuit current density (Jsc) of 13.1 mA cm −2 , a fill factor (FF) of 69%, and a power conversion efficiency (PCE) of 5.0%.

In photoelectrochemical (PEC) water splitting, charge separation and collection by the electric field in the photoactive material are the most important factors for improved conversion efficiency. Hence, ferroelectric oxides, in which electrons are the majority carriers, are considered promising photoanode materials because their high built-in potential, provided by their spontaneous polarization, can significantly enhance the separation and drift of photogenerated carriers. In this regard, the PEC properties of BiFeO3 thin-film photoanodes with different crystallographic orientations and consequent ferroelectric domain structures are investigated. As the crystallographic orientation changes from (001)pc via (110)pc to (111)pc, the ferroelastic domains in epitaxial BiFeO3 thin films become mono-variant and the spontaneous polarization levels increase to 110 μC/cm2. Consequently, the photocurrent density at 0 V vs. Ag/AgCl increases approximately 5.3-fold and the onset potential decreases by 0.180 V in the downward polarization state. It is further demonstrated that ferroelectric switching in the (111)pc BiFeO3 thin-film photoanode leads to an approximate change of 8,000% in the photocurrent density and a 0.330 V shift in the onset potential. This study strongly suggests that domain-engineered ferroelectric materials can be used as effective charge separation and collection layers for efficient solar water-splitting photoanodes.

A series of low band gap conjugated copolymers containing 9,10-modified phenanthrene and diketopyrrolopyrrole (DPP) units were synthesized as electron donor materials for bulk heterojunction organic solar cells. These donor-acceptor type PDPP copolymers have varying solubilizing groups on their identical conjugated backbones. The optical bandgap of PDPP copolymers is about 1.6 eV which corresponds to the long wavelength region of the solar spectrum. Through the incorporation of phenanthrene units into the conjugated backbone instead of commonly used thiophene derivatives, a higher open-circuit voltage of about 0.8 V could be achieved, as a result of their deeper HOMO level. Of all the devices, the P4:PC61BM BHJ system showed the best performance with a Voc of 0.79 V, a Jsc of 5.97 mA cm−2, a fill factor of 0.62 and a power conversion efficiency of 2.73% due to superior nanoscale phase separation between the electron donor and electron acceptor materials than in the other polymers arising from short-branched solubilizing groups on the phenanthrene side of its conjugated backbone.

We report on the fabrication of an organic thin-film semiconductor formed using a blend solution of soluble ambipolar small molecules and an insulating polymer binder that exhibits vertical phase separation and uniform film formation. The semiconductor thin films are produced in a single step from a mixture containing a small molecular semiconductor, namely, quinoidal biselenophene (QBS), and a binder polymer, namely, poly(2-vinylnaphthalene) (PVN). Organic field-effect transistors (OFETs) based on QBS/PVN blend semiconductor are then assembled using top-gate/bottom-contact device configuration, which achieve almost four times higher mobility than the neat QBS semiconductor. Depth profile via secondary ion mass spectrometry and atomic force microscopy images indicate that the QBS domains in the films made from the blend are evenly distributed with a smooth morphology at the bottom of the PVN layer. Bias stress test and variable-temperature measurements on QBS-based OFETs reveal that the QBS/PVN blend semiconductor remarkably reduces the number of trap sites at the gate dielectric/semiconductor interface and the activation energy in the transistor channel. This work provides a one-step solution processing technique, which makes use of soluble ambipolar small molecules to form a thin-film semiconductor for application in high-performance OFETs.

Two donor-acceptor (D-A) alternating conjugated polymers based on thienylenevinylene-benzotriazole (TV-BTz), PTV6B with a linear side chain and PTVEhB with a branched side chain, were synthesized and characterized for organic field effect transistors (OFETs) and complementary metal-oxide-semiconductor (CMOS)-like inverters. According to density functional theory (DFT), polymers based on TV-BTz exhibit a coplanar and rigid structure with no significant twists, which could cause to an increase in charge-carrier mobility in OFETs. Alternating alkyl side chains of the polymers impacted neither the band gap nor the energy level. However, it significantly affected the morphology and crystallinity when the polymer films were thermally annealed. To investigate the effect of thermal annealing on the morphology and crystallinity, we characterized the polymer films using atomic force microscopy (AFM) and 2D-grazing incidence X-ray diffraction (2D-GIWAXD). Fibrillary morphologies with larger domains and increased crystallinity were observed in the polymer films after thermal annealing. These polymers exhibited improved charge-carrier mobilities in annealed films at 200 °C and demonstrated optimal OFET device performance with p-type transport characteristics with charge-carrier mobilities of 1.51 cm

Four donor–acceptor (D–A) type conjugated polymers (PA1, PA2, PA3 and PA4) based on phenanthrene and naphthalene as the donating units with or without dimethoxy substitution were synthesized for organic field effect transistors (OFETs) and bulk-heterojunction organic photovoltaics (OPVs). Dimethoxy substituents have significant effects on the optical, electrochemical, charge transport and photovoltaic properties depending on the donor-polyaromatic (PA) compounds. The optical band gaps of these PA-based copolymers from the smallest to the largest are as follows: 1.52 eV (1,5-dimethoxy substituted naphthalene (PA4)), 1.59 eV (unsubstituted naphthalene (PA3)), and 1.63 eV (unsubstituted phenanthrene (PA1), and substituted 9,10-dimethoxy phenanthrene (PA2)). While the values vary depending on the compounds, both PA2 and PA4 are found to have higher highest occupied molecular orbital (HOMO) energy levels than those of PA1 and PA3 due to the electron donating nature of dimethoxy substituents. The PA based copolymers without dimethoxy substituents showed highly balanced ambipolar behavior with ∼1 cm2 V−1 s−1, whereas the electron mobility of dimethoxy modified PA (MeOPA) based copolymers was suppressed. The inverted bulk heterojunction OPVs based on PA1 and PA3 exhibited power conversion efficiency (PCE) as high as 5.3% and 5.8%, respectively. The PCEs of PA copolymer-based OPV devices were mainly affected by an increase in the open circuit voltage rather than by the photocurrent or fill factor.

An attractive synthetic strategy for incorporating a quinoidal molecule into a conjugated polymer backbone with three short steps is reported here. The quinoidal polymer, PQuBTV, exhibited high planarity and extended conjugation. As a result, ambipolar charge carrier mobilities of 0.52 cm2 V−1 s−1 for holes and 0.53 cm2 V−1 s−1 for electrons were observed in field-effect transistor devices.

Organometal trihalide perovskite solar cells (PeSCs) have recently opened a new era for photovoltaics power sources via the tremendous increase in power conversion efficiency (PCE) in the past five years. The next achievement will occur when scalable and processable PeSCs are realized because of a fundamental understanding of the interfacial characteristics and perovskite crystallization in PeSCs. Here, we report solution-processed planar PeSCs with well-tailored functional graphene, successfully demonstrating excellent module PCEs of 10.0% and 8.1% for rigid and flexible substrates, respectively, with active-area of 10 cm 2 . Systematic investigations reveal that molecular-doped reduced graphene oxide with fluorine atoms (MFGO) exhibits fast charge-extraction ability and well-aligned energetic interface characteristic due to its intrinsic structure, and MFGO promotes perovskite crystallization and orientation with minimized stoichiometric defects. The solution-processable graphene can function not only as an efficient and stable interlayer but also as an inducer of the crystallization of the perovskite layer in simplified device architectures without a complex process.