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Small-molecule acceptor (SMA)-based organic solar cells (OSCs) have achieved high power conversion efficiencies (PCEs), while their long-term stabilities remain to be improved to meet the requirements for real applications. Herein, we demonstrate the use of donor-acceptor alternating copolymer-type compatibilizers (DACCs) in high-performance SMA-based OSCs, enhancing their PCE, thermal stability, and mechanical robustness simultaneously. Detailed experimental and computational studies reveal that the addition of DACCs to polymer donor (

Understanding the effects of the chemical structures of donor polymers on the photovoltaic properties of their corresponding organic photovoltaic (OPV) devices under various light-intensity conditions is important for improving the performance of these devices. We synthesized a series of copolymers based on poly[(2,6-(4,8-bis(5-(2-thioethylhexyl)thiophen-2-yl)benzo[1,2

We report a series of new n-type random copolymers (P(NDI2OD-Se-Th x), where x = 0, 0.5, 0.7, 0.8, 0.9, 1.0) consisting of naphthalene diimide (NDI), selenophene-2,2′-thiophene (Se-Th), and seleno[...

In contrast to the red and green regions, conventional fluorescent emitters continue to serve as blue emitters in commercialized organic light-emitting diodes. Many researchers have studied anthracene moieties as blue emitters, given their appropriate energy levels and good emission properties. We herein report two new deep blue-emitting anthracene derivatives that include

Organic flash memories that employ solution-processed polymer semiconductors preferentially require internal stability of their active channel layers. In this paper, a series of new donor-acceptor copolymers based on cyclopentadithiophene (CDT) and diketopyrrolopyrrole (DPP) are synthesized to obtain high performance and operational stability of nonvolatile floating-gate memory transistors with various additional donor units including thiophene, thiophene-vinylene-thiophene (CDT-DPP-TVT), selenophene, and selenophene-vinylene-selenophene. Detailed analyses on the photophysical, two-dimensional grazing incident X-ray diffraction, and bias stress stability are discussed, which reveal that the CDT-DPP-TVT exhibits excellent bias stress stability over 10

We report two newly synthesized naphthalene diimide (NDI)-based conjugated polymers, poly[(E)-2,7-bis(2-decyltetradecyl)benzo[lmn][3,8]phenanthroline-1,3,6,8(2H,7H)-tetraone-vinylene-thiophene-viny...

Herein, we explore the strategy of realizing a red-selective thin-film organic photodiode (OPD) by synthesizing a new copolymer with a highly selective red-absorption feature. PCZ-Th-DPP, with phenanthrocarbazole (PCZ) and diketopyrrolopyrrole (DPP) as donor and acceptor units, respectively, was strategically designed/synthesized based on a time-dependent density functional theory calculation, which predicted the significant suppression of the band II absorption of PCZ-Th-DPP due to the extremely efficient intramolecular charge transfer. We demonstrate that the synthesized PCZ-Th-DPP exhibits not only a high absorption coefficient within the red-selective band I region, as theoretically predicted, but also a preferential face-on intermolecular structure in the thin-film state, which is beneficial for vertical charge extraction as an outcome of a glancing incidence X-ray diffraction study. By employing PCZ-Th-DPP as a photoactive layer of Schottky OPD, to fully match its absorption characteristic to the spectral response of the red-selective OPD, we demonstrate a genuine red-selective specific detectivity in the order of 1012 Jones while maintaining a thin active layer thickness of ∼300 nm. This work demonstrates the possibility of realizing a full color image sensor with a synthetic approach to the constituting active layers without optical manipulation.

Phenazasiline, a sp3 hybridized silicon-bridged diphenylamine, is a promising donor moiety for deep-blue TADF emitters because of its deep highest occupied molecular orbital, high triplet level of 3.1 eV, and orthogonal connection with acceptor moieties. Herein, we report highly efficient deep-blue TADF emitters composed of phenazasiline donor and triazine acceptor combined with methyl-substituted phenylene linkers. As a series of methyl-substituted linker-based TADF emitters, we also synthesized spiroacridine donor-based sky-blue TADF emitters to study the effect of methyl-substituted linkers on the photophysical properties of TADF emitters. Deeper blue emissions of TADF emitters were obtained by substituting either one or two methyl groups at the phenylene linker of TADF molecules, and a small singlet–triplet gap below 0.2 eV was maintained for efficient reverse intersystem crossing. Organic light-emitting diodes (OLEDs) with spiroacridine-based TADF emitters, TTSA and TXSA, showed external quantum effi...

To utilize the potential of small-molecule-based organic solar cells, proper designs of the photoactive materials which result in reasonable performance in a halogen-free solvent system and thickness tolerance over a range are required. One of the best approaches to achieve these requirements is via the molecular engineering of small-molecule electron donors. Here, we have modified a previously reported dithienobenzodithiophene (DTBDT)-based small molecule (SM1) via the dimerization approach, that is, the insertion of an additional DTBDT into the main backbone of the small molecule (SM2). An SM1-based photoactive film showed severe pinhole formation throughout the film when processed with a halogen-free o-xylene solvent. On the other hand, the modified small-molecule SM2 formed an excellent pinhole-free film when processed with the o-xylene solvent. Because of the dimerization of the DTBDT in the SM2 core, highly crystalline films with compact lamellae and an enhanced donor/acceptor interdigitation were formed, and all of these factors led to a high efficiency of 8.64% with chloroform and 8.37% with the o-xylene solvent systems. To the best of our knowledge, this study represents one of the best results with the SM donor and fullerene derivative acceptor materials that have shown the device performance with halogen-free solvents.

Vacuum-processed diphenylbis(3-(pyridine-2-yl)phenyl)silane (2PTPS), diphenylbis(3-(pyridine-3-yl)phenyl)silane (3PTPS), and diphenylbis(3-(pyridine-4-yl)phenyl)silane (4PTPS) have been used as electron-transporting host materials combined with tris(4-carbazoyl-9-ylphenyl)amine (TCTA) as the hole-transporting host, which induce balanced charge carrier transport for high-efficiency phosphorescent organic light-emitting diodes. The 4PTPS-based organic light-emitting diodes with tris[2-phenylpyridinato-C2,N]iridium(III) [Ir(ppy)3] dopant showed highest current efficiency and external quantum efficiency of 53.54 cd/A and 15.61%, compared to 2PTPS (40.75 cd/A, 11.84%) and 3PTPS (29.35 cd/A, 8.54%). These results were attributed to the well-aligned structure with preferential horizontal orientation of the emitting material layer by the diffraction intensity distribution as a function of azimuthal angle in two-dimensional grazing incidence X-ray diffraction analysis. The molecular orientation of TCTA:4PTPS material with a narrow azimuthal intensity distribution had better priority to the horizontal direction than the other TCTA:2PTPS and TCTA:3PTPS materials, which is related to the charge transport as well as the device efficiency. We found that the preferential horizontal orientation of the co-host material with a balanced charge carrier was not affected by Ir(ppy)3 dopant with a homoleptic structure and bis-[2-(4,6-difluorophenyl)pyridinato-N,C2](picolinato)iridium [Firpic] dopant with a heteroleptic structure in the co-host/dopant system.

We introduce a synthetic approach to enhance coalescence phenomenon during solidification of water-borne colloids so that thin, even, and continuous film morphology of polymer semiconductors can be realized. From the theoretical study of complex colloids, we show that small-sized and uniform colloid particles are essential to minimize depletion contact energy between colloid particles and thus to enhance coalescence. Therefore, the newly synthesized polymer semiconductor in this study is designed with the aim of better molecular affinity with surfactants, so that phase transfer of polymer semiconductors from organic phase to water phase can proceed more efficiently during mini-emulsion synthesis. This is achieved by substituting a Si atom to the branching C atom of the alkyl solubilizing group of a conventional donor–acceptor polymer semiconductor. Such a chemical modification increases the volumetric portion of hydrophobic alkyl chains and thus enables higher solubility as well as higher hydrophobicity, ...

We describe several strategies for the molecular design of high-efficiency blue fluorescent emitters. Asymmetric donor–acceptor (D–A) and symmetric A–D–A-type fluorescent emitters were designed with spiroacridine donors and diphenyltriazine acceptors. Substituting a toluene or xylene moiety for the phenyl group connecting the donor and acceptor and replacing the diphenylsilane group with a fluorene moiety resulted in a deeper blue emission without any losses in luminescence efficiency. On the basis of these substitutions, deep blue organic light emitting diodes (OLEDs) with Commission Internationale de L’Eclairage (CIE) coordinates of (0.149, 0.082) and an external quantum efficiency (EQE) of 7.7% were fabricated using a D–A-type emitter. Symmetrizing the D–A structure to an A–D–A structure increased the proportion of horizontally oriented emission dipoles in the organic film from 70 to 90%. OLEDs incorporating symmetric A–D–A-type emitters had EQEs as high as 8.5% due to increased outcoupling efficiencie...

Here, we synthesized a dihexyloxynaphthalene-based conjugated polymer (PNa6-Th) to realize narrowband blue-selective polymer photodiode. The optical, electrochemical, and thermal properties of the synthesized polymer were investigated. It was found that PNa6-Th exhibited a blue-selective absorption with a narrow full width at half-maximum of ∼100 nm and a wide optical band gap of ∼2.52 eV. We constructed a planar heterojunction structure with PNa6-Th and ZnO as a blue-selective electron donor and nonabsorbing acceptor, respectively; To enhance the photodiode performance, a minor amount of [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) was introduced on the donor layer. By introducing the PCBM on PNa6-Th layer, external quantum efficiency was increased from 5.4% for pristine device to 37.8% for 15 wt % PCBM-doped device, while the dark current values maintained nearly constant. This external quantum efficiency boost leads to high detectivity of 2.31 × 1012 Jones at −1 V. The physics behind the improved ...

A series of naphthalene diimide (NDI)-based small molecules were synthesized as nonfullerene acceptors and incorporated in all-small-molecule solar cells. Three NDI-based small molecules, NDICN-T, NDICN-BT, and NDICN-TVT, were designed with different linkers between two NDI units to induce the different conjugation length and modulate the geometric structures of the NDI dimers. The small NDI-based dimer electron acceptors with slip-stacked structures that facilitate π–π stacking interactions and/or hinder excessive aggregation exhibited different morphological behaviors, such as miscibility or crystallinity in bulk heterojunction blends with 7,7′-(4,4-bis(2-ethylhexyl)-4H-silolo[3,2-b:4,5-b′]dithiophene-2,6-diyl)bis(6-fluoro-4-(5′-hexyl-[2,2′-bithiophen]-5-yl)benzo[c][1,2,5]thiadiazole) (DTS-F) electron donors. The photovoltaic devices prepared with NDICN-TVT gave the highest power conversion efficiency (PCE) of 3.01%, with an open-circuit voltage (Voc) of 0.75 V, a short-circuit current density (Jsc) of ...

A new donor–donor copolymer consisting of phenanthro[1,10,9,8-cdefg]carbazole and thiophene unit (PP-Th) was synthesized for narrow band green-selective organic photodiode application. Thanks to well-defined intramolecular conjugation and inhibited intermolecular interaction of PP-Th compared to its donor–acceptor type analogues, PP-Th revealed narrow band green-selective absorption peak at 510 nm with low full width at half-maximum value of 98 nm. In addition, deep ionization energy of PP-Th, as confirmed by photophysical analyses, made it less susceptible to oxidational degradation. Green-selective organic photodiodes (OPDs) were fabricated utilizing PP-Th as a green absorbing donor material and ZnO as a nonabsorbing acceptor material. The optimized OPD rendered a very low dark current of 2 nA cm–2 and a high detectivity of 1.42 × 1012 Jones with narrow band green-selectivity. Moreover, PP-Th enabled OPD with a high 3-dB bandwidth of 3.1 kHz and a high linear dynamic range of 84.9 dB. Furthermore, the r...

To improve the charge carrier mobility of diketopyrrolopyrrole donor–acceptor copolymer semiconductors, the length of the donor building block is controlled using vinylene moieties, and its effects on crystalline structure and charge transport are systematically studied. We synthesize P29-DPP-TBT with two vinylene linkages between thiophene units and compare it with P29-DPP-TVT with single vinylene linkage. Density functional theory calculations predict enhanced backbone planarity of P29-DPP-TBT compared to P29-DPP-TVT, which can be related to the increased conjugation length of P29-DPP-TBT as proved by the increased free exciton bandwidth extracted from UV–vis absorption spectra and the wavenumber shift of the C–C peaks to higher values in Raman spectra. From two-dimensional grazing incident X-ray diffraction studies, it is turned out that the paracrystalline disorder is lower in P29-DPP-TBT than in P29-DPP-TVT. Near-edge X-ray absorption fine structure spectroscopy reveal that more edge-on structure of ...

The organic solar cell (OSC) performance of a series of new donor–acceptor copolymers containing indolo[3,2-b]indole as a key donor block and benzothiadiazole (BT) units with various degrees of fluorination as acceptors is reported. Compared with the simple carbazole unit, the strategically developed indolo[3,2-b]indole unit is found to significantly extend π-conjugation and thus increase the intermolecular interactions of the resulting copolymer, as probed by density functional theory calculations, photophysical studies, and structural/morphological analyses. In addition, fluorination of BT can facilitate nanostructuring of the copolymers, mainly due to further planarization of the backbone, which leads to apparently higher hole/electron charge carrier mobilities. The OSC properties of this series of new copolymers blended with fullerene show a strong dependence on the fine and continuous fibrous nanostructure of the blend film. The indolo[3,2-b]indole-based copolymer with singly fluorinated BT units pos...

A push–pull-type donor copolymer, named PP-TPD, was synthesized with the Suzuki coupling reaction using 6H-phenanthro[1,10,9,8-cdefg]carbazole (PCZ) as the donor unit and 1,3-bis(5-bromothiophen-2-yl)-5-octyl-4H-thieno[3,4-c]pyrrole-4,6(5H)-dione (TPD) as the acceptor unit. The synthesized PP-TPD was systematically investigated in terms of crystallinity and thermal, electrical, electrochemical, and optical properties. PP-TPD revealed green-selective absorption with a narrow full width at half-maximum of 138 nm. Green-selective organic photodiodes (OPDs) were constructed using PP-TPD as the green-absorbing donor and ZnO as the nonabsorbing acceptor material. The fabricated OPDs exhibited an extremely low dark current of 0.68 nA/cm2 at −5 V and a high detectivity above 1012 Jones at 550 nm. Moreover, they showed a sufficiently high 3-dB frequency and a linear dynamic range, similar to those of ideal-operating OPDs. The origin and physics background of the observed low dark current and high detectivity are d...

The photostability of donor–acceptor (D–A) polymers remains a critical issue despite recent improvements in the power conversion efficiencies (PCEs) of organic photovoltaic (OPV) cells. We report the synthesis of three highly photostable polymers (PDTBDT-BZ, PDTBDT-BZF, and PDTBDT-BZF2) and their suitability for use in high-performance OPV cells. Under 1 sunlight of illumination in air for 10 h, these polymer films demonstrated remarkably high photostability compared to that of PTB7, a representative polymer in the OPV field. While the PDTBDT-BZ, PDTBDT-BZF, and PDTBDT-BZF2 polymer films maintained 97, 90, and 96% photostability, respectively, a PTB7 film exhibited only 38% photostability under the same conditions. We ascribed the high photostability of the polymers to both the intrinsically photostable chemical moieties and the dense packing of alkyl side chains and planar backbone polymer chains, which prevents oxygen diffusion into the PDTBDT-BZ films. This work demonstrates the high photostability of ...

Control of electron and hole transport in conjugated molecules is a challenging but essential task for deeply understanding the intrinsic charge transport behaviors as well as technological benefits for optimizing the performance of various optoelectronic devices. Here we suggest a facile route to controlling ambipolar charge transport in conjugated polymers by precise regulation of the copolymerization ratio between a relatively large electron donor and acceptor building block as a repeating unit. By varying the ratio between poly[2,5-bis(2-octyldodecyl)pyrrolo[3,4-c]pyrrole-1,4(2H,5H)-dione-(E)-[2,2-bithiophen]-5-yl)-3-(thiophen-2-yl)acrylonitrile] (DPP-CNTVT) as an electron transport unit and DPP-selenophene-vinylene-selenophene (DPP-SVS) as a hole transport unit, mobility (μFET) and onset voltage (Von) in organic field-effect transistors are effectively modulated from p-channel [μFET,h = 6.23 ± 0.4 cm2 V–1 s–1] to n-channel [μFET,e = 6.88 ± 1.01 cm2 V–1 s–1] dominant transport. The same two DPP-based ...

For electroluminescence with delayed fluorescence, the azasiline unit has been introduced for the first time as a donor in a thermally activated delayed fluorescence (TADF) material. The TADF material (DTPDDA) shows strong intramolecular charge transfer (CT) character with large spatial separation with the acceptor of triazine leading to narrow splitting of singlet and triplet excited states for the efficient reverse intersystem crossing (RISC). A blue organic light emitting diode (OLED) based on DTPDDA not only displays deep blue in the Commission Internationale de L’Eclairage (CIE) coordinates of (0.149, 0.197) but also exhibits a high external quantum efficiency (EQE) of 22.3% which is the highest value ever reported for a blue fluorescent OLED. Theoretical prediction based on transient photoluminescence (PL) and optical simulation result agrees well with the achieved EQE indicating the successful conversion of triplet excitons to singlet in the blue fluorescent OLED by using DTPDDA.

It is important to develop new donor (D)–acceptor (A) type low band gap polymers for highly stable polymer solar cells (PSCs). Here, we describe the synthesis and photovoltaic properties of two D–A type low band gap polymers. The polymers consist of dithienobenzodithiophene (DTBDT) moieties with expanded conjugation side groups as donors and 2-ethyl-1-(thieno[3,4-b]thiophen-2-yl)hexan-1-one (TTEH) or 6-octyl-5H-thieno[3′,4′:4,5]thieno[2,3-c]pyrrole-5,7(6H)-dione (DTPD) as acceptors to give pDTBDT-TTEH and pDTBDT-DTPD polymers, respectively. The pDTBDT-TTEH is quite flat, resulting in a highly crystalline film. In contrast, the pDTBDT-DTPD is highly twisted to yield an amorphous film. Photovoltaic devices based on pDTBDT-TTEH and pDTBDT-DTPD exhibited power conversion efficiencies (PCEs) of 6.74% and 4.44%, respectively. The PCE difference results mainly from morphological differences between the two polymer:PC71BM blend films; the pDTBDT-TTEH polymer formed a nanoscopically networked domains in the blend ...

Systematic side-chain engineering has been performed for diketopyrrolopyrrole-selenophene vinylene selenophene (DPP-SVS) polymers to determine the optimal side-chain geometries for the most efficient charge transport, and the structure–property relationship has been thoroughly investigated using a range of analyses. A series of DPP-SVS polymers, ranging from 25-DPP-SVS to 32-DPP-SVS, with branched alkyl groups containing linear spacer groups from C2 to C9 has been synthesized, and the electrical performance of these polymers is significantly dependent on both the length of the spacer group and its odd–even characteristics. Spacer groups with even numbers of carbon atoms exhibit charge-carrier mobilities that are 1 order of magnitude higher than those with odd numbers of carbon atoms. The optimized charge transport has been obtained from 29-DPP-SVS with a C6 spacer, showing the maximum mobility of 13.9 cm2 V–1 s–1 (VGS, VDS = −100 V) and 17.8 cm2 V–1 s–1 (VGS, VDS = −150 V). Longer spacer groups deviate fr...

Random copolymerization strategy is introduced to increase the solubility of donor–acceptor copolymers so that they can be processed with environmentally benign, halogen-free solvents. Traditionally, it has been believed that the random copolymer with a lower crystalline order should have a significantly lower charge carrier mobility. This report shows that random copolymerization between two highly planar, charge-delocalized repeating units can significantly enhance the solubility while almost preserving the high charge carrier mobility. A comparative study was conducted for a series of random copolymers consisting of diketopyrrolopyrrole–thienothiophene (DPP-TT) and DPP–selenophene–vinylene–selenophene (DPP-SVS) with composition ratios of 10:0, 9:1, 7:3, 5:5, 3:7, 1:9, and 0:10 by using the crystalline order determined from grazing-incident X-ray diffraction measurements and charge carrier mobility determined from field effect transistor measurements. The results showed that the copolymer tends to have ...

Charge carrier mobility is still the most challenging issue that should be overcome to realize everyday organic electronics in the near future. In this Communication, we show that introducing smart side-chain engineering to polymer semiconductors can facilitate intermolecular electronic communication. Two new polymers, P-29-DPPDBTE and P-29-DPPDTSE, which consist of a highly conductive diketopyrrolopyrrole backbone and an extended branching-position-adjusted side chain, showed unprecedented record high hole mobility of 12 cm(2)/(V·s). From photophysical and structural studies, we found that moving the branching position of the side chain away from the backbone of these polymers resulted in increased intermolecular interactions with extremely short π-π stacking distances, without compromising solubility of the polymers. As a result, high hole mobility could be achieved even in devices fabricated using the polymers at room temperature.

The new deep-blue iridium(III) complexes, (TF)2Ir(pic), (TF)2Ir(fptz), (HF)2Ir(pic), and (HF)2Ir(fptz), consisting of 2',4″-difluororphenyl-3-methylpyridine with trifluoromethyl carbonyl or heptafluoropropyl carbonyl at the 3' position as the main ligand and a picolinate or a trifluoromethylated-triazole as the ancillary ligand, were synthesized and characterized for applications in organic light-emitting diodes (OLEDs). Density function theory (DFT) calculations showed that these iridium complexes had a wide band gap, owing to the introduction of the strong electron withdrawing perfluoro carbonyl group. Time-dependent DFT (TD-DFT) calculations suggested that their lowest triplet excited state was dominated by a HOMO → LUMO transition and that the contribution of the metal-to-ligand charge transfer (MLCT) was higher than 34% for all four complexes, indicating that strong spin-orbit coupling exists in the complexes. The 10 wt % (TF)2Ir(pic) doped 9-(3-(9H-carbazole-9-yl)phenyl)-3-(dibromophenylphosphoryl)-9H-carbazole (mCPPO1) film exhibited the highest photoluminescence quantum yield of 74 ± 3% among the films based on the four complexes. Phosphorescent OLEDs based on (TF)2Ir(pic) and (TF)2Ir(fptz) exhibited maximum external quantum efficiencies of 17.1% and 8.4% and Commission Internationale de l'Eclairage (CIE) coordinates of (0.141, 0.158) and (0.147, 0.116), respectively. These CIE coordinates represent some of the deepest blue emissions ever achieved from phosphorescent OLEDs with considerably high EQEs.

We demonstrate the synthesis of a new copolymer which is composed of dialkyl thienylated benzodithiophene and perfluororalkyl-carbonyl thienothiophene (DTBDT-TTFO) and the characterization of its optoelectronic properties. The introduction of thienyl groups enabled the extended delocalization of π electrons in the DTBDT-TTFO backbone and efficient intermolecular charge transport as proved by the fairly high field effect mobility of 0.02 cm(2)/(V s). The introduction of perfluororalkyl-carbonyl side chains resulted in a significant red-shift of DTBDT-TTFO in the absorption spectra and a decrease in the HOMO and LUMO levels. The resulting energy levels of DTBDT-TTFO were not satisfactory for solar cell applications, especially in terms of charge separation at the polymer/PCBM interfaces. Rather, the DTBDT-TTFO showed better energy level matching with the colloidal nanocrystals (NCs) of CdSe. A photodetector based on the bulkheterojunction of DTBDT-TTFO and CdSe NCs with coplanar device geometry resulted in a high photoconductive gain (responsivity higher than 1A/W under a low operating voltage of 1 V), possibly arising from electron trapping at CdSe NCs such that the hole can travel along the detector and its surrounding circuit. More importantly, the photodetector revealed a time constant of a few hundreds of microseconds, which means that the response speed of the photodetector is fast enough for lag-free imaging applications.

We report the synthesis, characterization, and solar cell properties of new donor–acceptor-type low band gap polymers (POBDTPD and PEBDTPD) that incorporate dialkoxybenzodithiophene (BDT) as the donor and N-octyl-2,7-dithia-5-azacyclopenta[a]pentalene-4,6-dione (DTPD) as the acceptor. The newly developed DTPD moiety was carefully designed to lower a band gap via strong interaction between donor–acceptor moieties and keep polymer energy levels deep. Remarkably, the DTPD acceptor moiety effectively widens the light absorption range of the polymers up to ∼900 nm while positioning their HOMO and LUMO levels in the optimal range, i.e., −5.3 and −4.0 eV, respectively, for high power conversion efficiencies (PCEs) as we intended. Solar cell devices were fabricated according to the structure ITO/PEDOT:PSS/photoactive (polymer:PC70BM)/TiO2/Al. The POBDTPD devices exhibited a PCE of 4.7% with a Voc of 0.70 V, a Jsc of 10.6 mA/cm2, and a FF of 0.64. The PEBDTPD devices yielded a higher PCE of 5.3% with a Voc of 0.72...

A series of new p-type polymers, PNDT-T and PNDT-TT, with enforced coplanar structure for effective π-electron delocalization, having naphtho[2,1-b:3,4-b′]dithiophene and thiophenes as main core units, were successfully synthesized by Stille coupling reaction. The naphtho[2,1-b:3,4-b′]dithiophene unit of the polymer main chain enhances charge carrier mobility by extending π-conjugation length and rigidly enforced coplanar structure. Both polymers, PNDT-T and PNDT-TT, have high thermal stability up to 250 °C with a high Tg of 402 °C. On the basis of AFM and XRD results, it was found that PNDT-TT showed relatively more highly ordered intermolecular structures than did PNDT-T, with thiophene unit and high field-effect mobility, because the bithiophene unit provides crystallinity with increasing planarity and enough space for interdigitation of the long alkyl side chains for high order. These new p-type polymers PNDT-T and PNDT-TT exhibit high carrier mobilities of 0.01 and 0.076 cm2/(V s) and on/off ratios o...

A new amorphous semiconducting polymer containing dodecylthiophene rings and a rigid thieno[3,2-b]thiophene ring, poly(2,5-bis(3'-dodecyl-2,2'-bithiophen-5-yl)thieno[3,2-b]thiophene) (NAP), was synthesized via a microwave-assisted Stille coupling reaction. The presence of the flexible unsubstituted thiophene ring units next to the rigid fused thiophene ring caused NAP to have an amorphous structure. This structure was confirmed by XRD, AFM, and computational calculations. In particular, the out-of-plane XRD patterns of NAP thin films exhibited no reflection peaks before or after the annealing process, indicating that the films had amorphous microstructures. In addition, AFM images of the NAP thin films showed amorphous surface morphologies with very small root-mean-square (rms) surface roughnesses of 0.3-0.5 nm, independent of surface treatment or heat treatment. Computational calculations performed to investigate the preferred conformation of the polymer confirmed the amorphous characteristics of the NAP structure. On the basis of these findings, we propose how an amorphous NAP semiconductor can maintain high carrier mobility. A NAP-based TFT device exhibited a very high carrier mobility of 0.02 cm(2) V(-1) s(-1) with an on/off ratio of 1 x 10(5) and a very small threshold voltage of -2.0 V. This carrier mobility is the highest yet reported for TFTs based on amorphous semiconductors. Thus, the present findings suggest that an amorphous semiconductor layer comprised of NAP would be suitable for use in high-performance organic TFTs fabricated via simple processes in which neither surface treatment nor heat treatment is necessary.

Poly(5′,5′′-bithiophene-alt-2,6-[(1,5-didecyloxy)naphthalene]) (PBDN) was synthesized from 2,6-dibromo-l,5-didecyloxynaphthalene and 1,1′-[2,2′-bithiophene]-5,5′-diylbis[1,1,1-trimethylstannane] and was used as the active layer in organic thin-film transistors (OTFTs) and organic photovoltaic cells (OPVs). The obtained PBDN was soluble in organic solvents such as chloroform, chlorobenzene, and toluene and had a weight-averaged molecular weight of 9100, with a polydispersity index of 1.31. The photoluminescence (PL) maximum of the polymer was found at 500 and 530 nm in solution and at 567 nm in the film state, respectively. The highest occupied molecular orbital (HOMO) level of PBDN was low (−5.38 eV, ultraviolet photoemission spectroscopy and cyclic voltammetry), and the solution-processed thin-film transistors (TFTs) prepared using this polymer only showed a minimal change in their performance (

We have prepared a series of highly efficient and pure blue-emitting polyfluorene (PF)-type polymers that contain 9,9-di(9,9-dihexylfluoren-2-yl)fluorene and 9-(9,9-dihexylfluoren-2-yl)-9-(3,4-di(2-methyl)butyloxyphenyl)fluorene units. The photoluminescence (PL) results show that the size of the side groups strongly influences the color purity and color stability because of the superior ability of large groups to prevent interchain interactions between polymer chains. In contrast to n-octyl functional groups, the PF with 9,9-(dihexylfluoren-2-yl) and 3,4-di(2-methyl)butyloxyphenyl side groups exhibits good PL characteristics as a blue-light-emitting polymer (LEP), showing highly enhanced color integrity and color stability against oxidative conditions over PFs based on 9,9-dioctylfluorene. When N4,N4′-bis(4-methoxyphenyl)-N4,N4′-diphenylbiphenyl-4,4′-diamine (13) is incorporated into the polymer backbone, the polymer exhibits a highly efficient electroluminescence performance with a luminous efficiency of...

We have synthesized a new p-type polymer, poly[(1,2-bis-(2′-thienyl)vinyl-5′,5′′-diyl)-alt-(9,9-dioctyldecylfluorene-2,7-diyl] (PTVTF), via a Suzuki coupling reaction. PTVTF was found with UV–vis absorption spectroscopy, GIXD, AFM, and NEXAFS to be an ‘annealing-freeʼ amorphous polymer. Despite its amorphous nature, our time-of-flight measurements demonstrate that PTVTF is a good hole transport material with an intrinsic hole mobility of 2 × 10−4 cm2/Vs, which is comparable to those of crystalline polymers such as P3HT. A solution-processed PTVTF FET with a bottom gate/top contact geometry was found to exhibit good device performance with superior reproducibility. The field-effect mobility of holes was found to be 2 × 10−2 cm2/Vs with a good subthreshold swing of 1.7 Vdecade−1. The output characteristics indicate that good saturation and ohmic contact are present. The amorphous nature of PTVTF makes it a very promising candidate for commercial OTFTs since its properties are independent of fabrication cond...

New soluble anthracene derivatives containing thiophene and phenylenevinylene derivatives were synthesized via well-known synthetic routes. TIPS derivatives were added at the 9,10-positions of anthracene for the solubility and crystallinity. Both of the molecules were found to be promising for high charge mobility and stable organic semiconductors. The soluble anthracene core (TIPSAnt) is a potential precursor for the synthesis of novel semiconducting materials.

The new semiconductors that were composed of a naphthalene or anthracene core unit and alkylated thienothiophene on both sides, 2,6-bis(5‘-hexyl-thieno[3,2-b]thiophen-2‘-yl)naphthalene (DH-TNT) and 2,6-bis(5‘-hexyl-thieno[3,2-b]thiophen-2‘-yl)anthracene (DH-TAT), were synthesized by Suzuki coupling reaction. The obtained oligomers were characterized by FT-IR, mass and elemental analysis, UV−visible spectroscopy, cyclovoltammetry, differencial scanning calorimetry, and thermogravimetric analysis. Vacuum-evaporated films were characterized by X-ray diffraction and atomic force microscopy (AFM). They all form highly ordered polycrystalline vacuum-evaporated films. DH-TAT exhibits excellent field-effect performances, with a hole mobility of 0.14 cm2/Vs, an on/off current ratio of 6.3 × 106, and a good threshold voltage of −14 V when it was deposited at Ts = 120 °C on HMDS-treated SiO2. DH-TNT shows a hole mobility of 0.084 cm2/Vs and an on/off current ratio of 8.8 × 105 when it was deposited at Ts = 100 °C.

The novel spirobifluorene diamine monomer, 2,7-bis-amino-2‘,7‘-di-tert-butyl-9,9‘-spirobifluorene, was obtained. The new organosoluble polyimides were prepared from spirobifluorene diamine containing bulky tert-butyl group and conventional dianhydrides as well as 2,2‘-bis(4‘ ‘-tert-butylphenyl)-4,4‘,5,5‘-biphenyltetracarboxylic dianhydride (BBBPAn) and 2,2‘-bis(4‘ ‘-trimethylsilylphenyl)-4,4‘,5,5‘-biphenyltetracarboxylic dianhydride (BTSBPAn), which are composed of a noncoplanar twisted biphenyl unit containing bulky p-tert-butylphenyl groups and/or p-trimethylsilylphenyl groups by high-temperature one step polymerization. The structures of polymers were confirmed by various spectroscopic techniques. The weight-average molecular weights and polydispersities of resulting polymers were in the ranges 48 300−183 900 and 2.10−3.26, respectively. The bulky and twisted noncoplanar structural feature confers an enhanced solubility of the polyimides because of a decrease in the degree of molecular packing and crys...

The sterically hindered and highly thermal stable spirobifluorenyl-substituted poly(p-phenylenevinylene) derivative was synthesized by Gilch polymerization. The defect-free polymer structure was characterized by various spectroscopies. The polymer was completely soluble in common organic solvents, and it had high thermal stability with high Tg of 205 °C. The polymer film showed maximum emission at 515 nm with a shoulder peak at around 560 nm and showed photoluminescence efficiency of 26 ± 5%. The study of thermal annealing of PL spectrum showed inhibited excimer formation. A cyclic voltammetry study revealed that the HOMO and LUMO energy level of the polymer are 3.08 and 5.46 eV, respectively. The EL spectrum from the device using polymer as emitting material showed a maximum peak of 515 nm, corresponding to the green region (x = 0.31, y = 0.61) in CIE (Commission Internationale de l'Eclairage) chromaticity coordinates. The LED based on polymer was shown to have a maximum brightness of 1155 cd/m2 at 12.6 ...

The two new dianhydrides, 2,2‘-bis(4‘ ‘-tert-butylphenyl)-4,4‘,5,5‘-biphenyltetracarboxylic dianhydride (BBBPAn) and 2,2‘-bis(4‘ ‘-trimethylsilylphenyl)-4,4‘,5,5‘-biphenyltetracarboxylic dianhydrid...

Fluorinated poly(arylene ether sulfide)s containing an ethynyl group (E-FPAESI) were synthesized by nucleophilic aromatic substitution from 4,4'-(hexafluoroisopropylidene)diphenol (6FBPA) and an excess of pentafluorophenyl sulfide, followed by reaction with 3-ethynylphenol. The molecular weights (M n 's) and polydispersities (M w /M n 's) of the E-FPAESI determined by GPC with polystyrene standard were in the range 14 200-25 200 and 2.23-2.47, respectively. The polymer films were fabricated by spin-coating and cross-linked by thermal curing. The cured films had good chemical resistance for common solvents such as acetone, tetrahydrofuran (THF), methylene chloride, chloroform, N,N-dimethyl-formamide (DMF), and dimethyl sulfoxide (DMSO). The glass transition temperature of E-FPAESI was changed from 120 to 160 °C after curing and showed high thermal stability up to 489 °C. At 1.55 um wavelength, the refractive indices and birefringences of the films were in the range 1.5200-1.5515 and 0.0034-0.0044, respectively, depending on feed ratio of 6FBPA and 4,4'-(trifluoromethylphenylisopropylidene)diphenol (3FBPA). The optical loss for E-FPAESI was measured to be less than 0.40 dB/cm.

A blue electroluminescent polymer, poly(biphenylenevinylene) derivative containing a bulky fluorenyl group, was prepared by the nickel-catalyzed coupling reaction. The structure and properties of t...

We report here the effect of size and type of substituents upon the fine and conformational structure and unusual optical absorption behavior for the substituted poly(1,6-heptadiynes). 4-(Carboxy-3-(trimethylsilyl)-1-propyl)-1,6-heptadiyne (1a), 4,4-bis(3-(trimethylsilyl)-1-propyl) dipropargylmalonate (1b), 4,4-bis[(acetoxy)methyl]-1,6-heptadiyne (2a), 4,4-bis[(ethylcarboxy)methyl]-1,6-heptadiyne (2b), 4,4-bis[(tert-butyldimethylsiloxy)methyl]-1,6-heptadiyne (3a), and 4,4-bis[(tert-butyldiphenylsiloxy)methyl]-1,6-heptadiyne (3b) were all prepared and polymerized to give organo-soluble polymers in high yield with MoCl5-based catalysts. From a series of λmax values of the polymers, we have found that incorporation of a bulkier substituent in the 4-position of 1,6-heptadiyne forces the conjugated polyene into a more planar structure, as indicated by the bathochromic shift of maximum absorption bands resulting from the π−π* transition of the conjugated polymer backbone. It appears that chain twisting of the s...

La cyclopolymerisation catalysee par des systemes a base de MoCl 5 ou de WCl 6 et de AlEt 2 Cl donne des polymeres conjugues contenant des motifs cyclohexene, solubles dans les hydrocarbures aromatiques et dans certains ethers et cetones. Il possede une excellente stabilite thermique, est stable a l'air et il presente une morphologie fibrillaire. La conductivite electrique maximale du polymere dope atteint 10 −4 S/cm