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Functional materials impact every area of our lives ranging from electronic and computing devices to transportation and health. In this Perspective, we examine the relationship between synthetic discoveries and the scientific breakthroughs that they have enabled. By tracing the development of some important examples, we explore how and why the materials were initially synthesized and how their utility was subsequently recognised. Three common pathways to materials breakthroughs are identified. In a small number of cases, such as the aluminosilicate zeolite catalyst ZSM-5, an important advance is made by using design principles based upon earlier work. There are also rare cases of breakthroughs that are serendipitous, such as the buckyball and Teflon(R). Most commonly, however, the breakthrough repurposes a compound that is already known and was often made out of curiosity or for a different application. Typically, the synthetic discovery precedes the discovery of functionality by many decades; key examples include conducting polymers, topological insulators and electrodes for lithium-ion batteries., Comment: 15 pages, two figures

The development of air-stable organic semiconductors (OSCs) with high charge mobilities is of pivotal importance for practical applications of organic thin film transistors (OTFTs) in various fields. Although several OSCs with high hole mobilities have been realized, their n-type counterparts lag far behind in terms of charge mobilities and especially air-stability potentially due to the highly sensitive nature of electrons to ambient oxidants. Isothianaphthene, a kind of non-classical thiophene, possesses a unique electronic structure and isothianaphthene bismide (BTDI) has been demonstrated as an efficient core for stable n-type OSCs. In this work, we introduced two fluoric groups with different alkyl-chains at the N-position of isothianaphthene-2,3,6,7-tetracarboxylic acid diimide and obtained new air-stable n-type OSCs, BTDI-OCF3 and BTDI-CF. The distinct length of the alkyl-chains caused different molecular packing styles of the resulting materials, as revealed by atomic force microscopy. The crystallinity of BTDI-OCF3 is found to be much better than BTDI-CF and single crystals of BTDI-OCF3 could easily be obtained by solution process. Besides, OTFTs based on these new semiconductors showed almost no hysteresis when tested in a glovebox and very small hysteresis is observed in air with a small decay of current, indicating good stability of both of these materials for their applications in n-type OTFTs.

This small contribution about Prof. Jan C. (Kees) Hummelen shows a part of his scientific life that involved his stay at UCSB and subsequent developments that were influenced by it. The article concentrates on Kees’ major contributions to fullerene research and to organic materials science, particularly organic electronics.

Nonfullerene acceptors are important for increasing the power conversion efficiency of organic bulk heterojunction (BHJ) solar cells. The number of well-performing nonfullerene acceptors is still relatively limited compared to the wide range of donor materials making it difficult to find donor–acceptor pairs with matching optical and electronic properties. We report the synthesis of three sulfur-annulated fused perylene diimide-based compounds (2PDI-2S, 2PDI-3S, and 2PDI-4S) that have varying electron affinity. BHJ solar cells with these acceptors and the donor polymer PTB7-Th have solar power conversion efficiencies above 5% with relatively high fill factors (>60%) for nonfullerene acceptors. The origin of the performance of the BHJs was studied using a combination of physical and optoelectronic characterization methods. X-ray scattering revealed that the domains of 2PDI-nS acceptors are disordered in neat films and in BHJs. The carrier mobility was highest for 2PDI-4S leading to the highest fill factor ...

Hybrid organic inorganic perovskite (HOIP) semiconductors can be used to fabricate thin film solar cells with high solar power conversion efficiencies. The stability of HOIP solar cells depends strongly on the hole and electron transport layers that encapsulate the semiconductor and prevent reactions with metallic electrodes. A series of fused perylene diimide-based compounds with varying degrees of sulfur annulation (2PDI, 2PDI-2S, 2PDI-3S, and 2PDI-4S) were examined as electron transport layers in methyl ammonium lead iodide (MAPbI3) solar cells. The sulfur annulation alters not only the electron affinity of the ETL, but also the chemical interaction with the MAPbI3 layer, resulting in unusually long lifetimes for this class of devices. Devices with 2PDI-4S, which contain two disulfide bridges, as an ETL show little degradation of the power conversion efficiency after 400 hours during solar illumination at the maximum power point, thus exceeding the performance of fullerene ETLs under long time operation.

Perovskite-derived hybrid platinum iodides with the general formula A2PtIVI6 (A = formamidinium FA and guanidinium GUA) accommodate excess I2 to yield hydrogen-bond-stabilized compounds where the I2 forms catenates with I− anions on the PtI6 octahedra.

Dibenzo thiophene- and selenophene are widely used in very different areas, ranging from biology to electronic engineering. However, their compounds require multiple synthetic steps. In this report, we introduce a two-step facile synthesis of a dibenzo thiophene/selenophene, namely diindeno[1,2-b:2′, 1′-d]thiophene-10, 11-dione (DITD) and diindeno[1,2-b:2′, 1′-d]selenophene-10, 11-dione (DISD). The compounds were further converted via a Knoevenagel condensation to dicyanovinylene derivatives. Their electronic and optoelectronic properties, backed by density functional theory (DFT) calculations are reported.

Noble metal halide compounds are an exciting class of materials which display unique crystal chemistry with temperature and pressure. Here we report two new compounds, single-valence formamidinium platinum iodide [(FA)2PtIVI6] and mixed-valence methylammonium gold iodide [(MA)2AuIAuIIII6]. Structural changes between 300 K and 100 K have been monitored. The compounds crystallize in two different perovskite-related structure classes, with the added complexity of a disordered, “tumbling”, organic cation at 300 K. This tumbling is significantly reduced at 100 K. (FA)2PtIVI6 undergoes in-phase octahedral tilting similar to related vacancy-ordered perovskite materials. At 100 K, (MA)2AuIAuIIII6 undergoes a transition which facilitates stronger Au–I covalent bonding as made evident by a contraction of the unit cell and distances between Au and I atoms in the ab plane.

We demonstrate a novel crosslinked disulfide system as a cathode material for Li-S cells that is designed with the two criteria of having only a single point of S−S scission and maximizing the ratio of S−S to the electrochemically inactive framework. The material therefore maximizes theoretical capacity while inhibiting the formation of polysulfide intermediates that lead to parasitic shuttle. The material we report contains a 1:1 ratio of S:C with a theoretical capacity of 609 mAh g−1. The cell gains capacity through 100 cycles and has 98 % capacity retention thereafter through 200 cycles, demonstrating stable, long-term cycling. Raman spectroscopy confirms the proposed mechanism of disulfide bonds breaking to form a S−Li thiolate species upon discharge and reforming upon charge. Coulombic efficiencies near 100 % for every cycle, suggesting the suppression of polysulfide shuttle through the molecular design.

Solution-processable organic metal halide compounds, such as methylammonium lead iodide (CH3NH3PbI3), possess unique optical and electronic properties such as long carrier lifetimes and high charge carrier mobility. Here we study a layered, 2-dimensional hybrid halide compound: methylammonium lead thiocyanate iodide ((CH3NH3)2Pb(SCN)2I2). Films deposited from solution are observed to grow with strong preferential alignment of 2-dimensional layers parallel to the substrate. The charge-transport properties of carriers in the 2-dimensional planes of (CH3NH3)2Pb(SCN)2I2 were measured using the contactless electronic characterization technique time-resolved microwave conductivity (TRMC). TRMC measurements show that the sum of the electron and hole charge carrier mobilities in (CH3NH3)2Pb(SCN)2I2 is above 1 cm2 V−1 s−1 and that the carrier lifetime is relatively long.

Two new compounds containing tetrathiafulvalene (TTF) cations with extended and discrete anions based on Bi and I are reported. The compound (TTF)BiI4 comprises [BiI2I4/2]− chains of edge-shared octahedra that are interspersed with stacks of TTF+•. The compound (TTF)4BiI6 has mixed-valence stacks of TTF and TTF+• and discrete molecules of TTF+• separated by discrete [BiI6]−3 anions. The optical and electrical transport properties of these compounds are reported. Due to the mixed-valence stacks of TTF, (TTF)4BiI6 is the significantly better electrical conductor than (TTF)BiI4, despite the discrete nature of the inorganic moiety.

We report the preparation and X-ray crystallographic characterization of the first crystalline homoatomic polymer chain, which is part of a semiconducting pyrroloperylene-iodine complex. The crystal structure contains infinite polyiodide I∞ (δ-) . Interestingly, the structure of iodine within the insoluble, blue starch-iodine complex has long remained elusive, but has been speculated as having infinite chains of iodine. Close similarities in the low-wavenumber Raman spectra of the title compound and starch-iodine point to such infinite polyiodide chains in the latter as well.

(TTF)Pb 2 I 5 : a Radical Cation-Stabilized Hybrid Lead Iodide with Synergistic Optoelectronic Signatures Hayden A. Evans, †,‡,§ Anna J. Lehner, § John G. Labram, ∥ Douglas H. Fabini, §,⊥ Omar Barreda, § Sara R. Smock, ‡ Guang Wu, ‡ Michael L. Chabinyc, ∥ , ⊥ * Ram Seshadri, †,‡,§,⊥ * and Fred Wudl ‡,§,⊥ * Mitsubishi Chemical Center for Advanced Materials, University of California, Santa Barbara, CA 93106 Department of Chemistry and Biochemistry, University of California, Santa Barbara, CA 93106 Materials Research Laboratory, University of California, Santa Barbara CA 93106 California NanoSystems Institute, University of California, Santa Barbara CA 93106 ⊥ Materials Department, University of California, Santa Barbara, CA 93106, USA. ABSTRACT: Hybrid organic inorganic materials offer the opportunity to combine functionalities of two distinct chemis- tries. Tetrathiafulvalene (TTF) is the precursor to some of the first organic metals, and perovskite lead iodides have re- cently proved their efficacy as photovoltaic materials. Here we describe a hybrid material that incorporates both, compris- ing TTF radical cations stabilizing an anionic layered lead–iodide network. Preparation, property analysis, and DFT calcu- lations are reported, verifying that (TTF)Pb 2 I 5 is a narrow gap semiconductor with optical properties synergistically influ- enced by the TTF +• radical cation. This radical cation contributes to states in the electronic gap formed by orbitals in the inorganic framework. Hybrid organic-inorganic materials can potentially combine the properties of highly tunable functional or- ganics with those of complementary inorganic networks in a single material. Distinct control over what is desired from each component becomes possible in such materi- als, allowing the functions of the organic and inorganic components to work synergistically. Tetrathiafulvalene (TTF), the organic component in the new hybrid material reported here, is a precursor to some of the early organic metals and was a clear choice when choosing a functional organic. It was first reported by Wudl et al. in the early 1970's, 1,2 and has been studied for its impressive electron donating abilities, 3,4 including derivatives displaying su- perconductivity. 5 Hybrid compounds containing TTF have also shown novel electronic and magnetic properties. Devic et al. 6,7 reported a ethylenedithio-1,2-diiodotetrathiafulvalene (EDT-TTF-I 2+• ) hybrid with metallic character, and showed its metal-insulator transition to be preserved within a hybrid compound with PbI 2 . Kondo et al. 8 simi- larly reported TTF +• hybrids containing Sn and Cl/Br, all which display semiconducting behavior due to interac- tions through the extended TTF networks. Magnetic compounds with TTF derivatives have also been made with transition metal halides, and found to be composed of two kinds of donor columns which magnetically couple with the anions through close contact between metal hal- ide interactions. 9 Metal-organic-frameworks (MOFs), a related class of hybrid materials, generally possess poor electronic functionality, but attempts to prepare electri- cally conductive MOFs have recently been made. Exam- ples include incorporating a conjugated molecule within the framework directly, 10 as a guest that electronically couples metal atoms in the framework using (TCNQ), 11 or post-synthetic modification of an insulating MOF via chemical leaching. 12,13 Stavila et al. 14 have recently re- viewed this topic. Layered lead halides, in their own right, are an attractive set of materials with rich optoelectronic and semiconducting behavior. The extensive work of Mitzi and coworkers 15,16 in the late 90’s first highlighted how amines and diammines combine with main group halides to form unique layered perovskite structures, which moti- vated the chemistry of organic ammonium cation “spac- ers” to flourish. Following the work of Kojima et al. 17 demonstrating the use of perovskite CH 3 NH 3 PbI 3 materi- als as solution deposited photovoltaics, there has been a huge flurry of research in this space to enhance the stabil- ity of the air unstable compound. This has included the use of ammonium spacer chemistry by Smith et al. 18 which improved stability of a layered perovskite incorpo- rating phenylethylammonium ions into the structure. Cao et al. 19 also explored this idea with butylammonium in- stead of phenylethylammonium, and reported that the extent of ammonium spacer incorporation as well as growth direction of subsequent films had significant im

Two novel s-indacene 1,3,5,7-tetraone derivatives, DTID-Hep2 and iso-DTID-Hep2, were synthesized and fully characterized. The controllable solid-state phase transformation of the crystals was studied. The unique thermally induced polymorphic transformations suggest that the two materials are interesting for potential applications not only in organic optoelectronics but also in switchable molecular actuators.

Perovskite-derived hybrid platinum iodides with the general formula A2PtIVI6 (A = formamidinium FA and guanidinium GUA) accommodate excess I2 to yield hydrogen-bond-stabilized compounds where the I2 forms catenates with I- anions on the PtI6 octahedra.

We describe the solid-state structural evolution in four hybrid hexaiodoplatinate(IV) compounds, demonstrating the increasingly important role that extended hydrogen bonding plays in directing the structure across the series. The compounds are A2PtI6, where A is one of the following amines: ammonium, NH4+; methylammonium, CH3NH3+; formamidinium, CH(NH2)2+; guanidinium, C(NH2)3+. These are closely related in structure and properties to the hybrid halide perovskites of lead(II) that have recently established their prowess in optoelectronics. The first three of these compounds crystallize in the vacancy-ordered double perovskite A2Pt□I6 (□ indicates a vacant site) structure in the K2PtCl6 archetype, despite the relatively large perovskite tolerance factors involved. The last compound, (GUA)2PtI6, crystallizes in a vacancy-ordered variant of the hexagonal CsNiCl3 structure: the K2MnF6 structure. A combination of solid-state 195Pt and 1H NMR spectroscopy and detailed density functional theory calculations help...

An in-depth discussion of the properties of perylene is presented. Tuning the properties of perylene by introducing nitrogens is also explored. Finally, we do not discuss the synthesis and properties of oligorylenes functionalized with dicarboxyimide bonds.

A high-yielding synthesis of a series of polyimide dendrimers, including decacyclene- and perylene-containing dendrimer D6, in which two types of polyimide dyes are present, is reported. In these constructs, the branching unit is represented by trisphenylamine, and the solubilizing chains by N-9-heptadecanyl-substituted perylene diimides. The photophysical properties of the dendrimers have been studied by absorption, steady-state, and time-resolved emission spectroscopy and pump–probe transient absorption spectroscopy. Photoinduced charge-separated (CS) states are formed on the femtosecond timescale upon visible excitation. In particular, in D6, two different CS states can be formed, involving different subunits that decays independently with different lifetimes (ca. 10–100 ps).

Our current civilization belongs to the organic materials age. Organic materials science pervades nearly all aspects of our daily life. This essay sketches the evolution of materials science up to the present day. Plastics as textiles and structural materials dominate human civilization. The element carbon is at the core of this development because of its diverse interconnections with itself and other elements of the periodic table. While silicon will not be supplanted from its role in electronics, carbon will provide the most versatile electronics applications, through inexpensive, flexible electronic devices.

The first observation that PBBTPD, a low bandgap, ambipolar conjugated donor-acceptor (DA) polymer based on benzobisthiadiazole (BBT), possesses an open-shell singlet ground state as well as a thermally accessible triplet state is described. Similarly, interesting electronic behavior in semiconducting organic DA oligomers based on BBT is also observed. Theoretical predictions have suggested that such behavior is due to the biradicaloid character of BBT and we provide experimental evidence indicating that these predictions are correct. Furthermore, the open shell character strengthens as the conjugation length increases, as observed in the BBT-based polymer, PBBTPD. We show that this biradicaloid structure is observed in each BBT moiety along the chain and that therefore PBBTPD is in fact a polyradicaloid. This observation will most likely aid in the development of better n-type polymeric acceptors for organic semiconductor applications. (c) 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015, 53, 287-293

We provide an overview of the current progress in the synthesis of poly(p-phenylene vinylene) (PPV) polymers. The described synthetic approaches can be divided into four main categories: polymerization of quinodimethane intermediates, metathesis polymerization, nucleophilic polycondensation, and palladium-catalyzed cross-coupling. While such variety is remarkable and very high-molecular-weight PPV can be prepared by some methods, the synthetic chemistry of PPV still limits the structural variety and purity of arylene vinylene polymers. In particular, palladium-catalyzed cross-coupling reactions, the method of choice in the contemporary conjugated polymer chemistry, often shows limited success in PPV series. On the other hand, the possibility of using metathesis polymerization creates new opportunities not available for other classes of conjugated polymers.

We report the first example of a stable pyrenotriazinyl radical, 1,3-diphenyl-1,2,4-pyrenotriazin-4-yl (PyT). Magnetic susceptibility measurements of the radical PyT show a transition from a paramagnetic state to an antiferromagnetic state. The pyrene moiety has a strong influence via ππ interactions in 1D chain stacks that result in the observed magnetic properties. Unexpectedly, the pyrene unit has essentially no effect on the electronic structure of the triazinyl core. Chemical sensing studies on various nitrophenol-based compounds showed that the radical PyT exclusively senses picric acid (PA), as a pH sensor, with a detection limit of 5.0×10−6 M.

Spintronics involves the study of spin directions manipulation in the solid-state and has been a fascinating and attractive field for scientists. In the past decade, organic materials, unlike inorganic solids, have emerged as one of the promising candidates for spintronics due to their low spin–orbit coupling and weak hyperfine interaction. Organic semiconductors have shown great potential for spin transport in recent publications. In this article, we address the issues of influence of organic materials in spin transport and introduce a variety of possible candidate organic materials for further development of the field.

Bulk heterojunction photovoltaic devices consisting of a novel non-fullerene acceptor based on a decacyclene triimide core and the common polymer donor poly(3-hexylthiophene) exhibit good power conversion efficiency (∼1.6%) as-cast. However, thermal annealing results in a drastic decrease in both the efficiency and the electron current. Polarized soft X-ray spectroscopy and grazing incidence X-ray scattering reveal that thermal annealing results in a reorientation of the acceptor molecules to an edge-on orientation with their π–π stacking direction predominantly in-plane with the substrate and overall hexagonal packing among planar columnar structures. This packing motif greatly hinders vertical electron transport in bulk heterojunction films. Furthermore, in situ X-ray scattering studies show that this critical reorientation occurs even at relatively low temperatures (∼60 °C). These results are some of the first to highlight differences between the morphology of non-fullerene and fullerene-based bulk heterojunctions and critical parameters that must be controlled when designing future high-performance non-fullerene acceptor molecules.

Rubicene, a molecular fragment of C70, is a promising organic semiconductor material that displays excellent electronic characteristics for use in organic field-effect transistors (OFETs). Bottom-gate/bottom-contact polycrystalline thin-film OFETs using rubicene exhibit a saturation hole mobility of 0.20 cm2 V−1 s−1 and a current on/off ratio (Ion/Ioff) of 1.0 × 104. In addition, the device performance can be improved with a mobility of 0.32 cm2 V−1 s−1 and Ion/Ioff of 2.5 × 104 with pentafluorobenzenethiol (PFBT) self-assembled monolayer (SAM) treatment on Au electrodes. To characterize the interfacial electronic structure and morphology of rubicene on Au and PFBT/Au, ultraviolet photoelectron spectroscopy (UPS), theoretical calculation with density functional theory (DFT) and grazing incidence X-ray diffraction (GIXD) were performed. With PFBT SAM treatment, the hole injection barrier from Au to rubicene is significantly decreased from 1.15 to 0.48 eV due to the formation of a large interface dipole on Au that increased its work function from 4.33 to 5.67 eV. Furthermore, PFBT SAM treatment also induces an “edge-on” configuration of rubicene, which can lead to the increase in carrier mobility. These results indicate that rubicene can serve as a benchmark organic semiconductor for model charge transport studies and in various organic electronic devices.

This Introductory Lecture is intended to provide a background to Faraday Discussion 174: “Organic Photonics and Electronics” and will consist of a chronological, subjective review of organic electronics. Starting with “ancient history” (1888) and history (1950–present), the article will take us to the present. The principal developments involved the processes of charge carrier generation and charge transport in molecular solids, starting with insulators (photoconductors) and moving to metals, to semiconductors and ending with the most popular semiconductor devices, such as organic light-emitting diodes (OLEDs), organic field effect transistors (OFETs) and organic photovoltaics (OPVs). The presentation will be from an organic chemistry/materials point of view.

The main advantages of Lithium-Sulfur batteries are the high theoretical specific capacity of elemental sulfur and the sustainability of sulfur-based materials over toxic, expensive heavy metals such as cobalt. Sulfur can theoretically achieve 1675 mAh g–1 through a conversion mechanism, but due to the parasitic polysulfide shuttle problem, the capacity rapidly fades. We demonstrate new crosslinked disulfides as promising cathode materials for Li–S cells that are designed to have only a single point of S–S scission, preventing the formation of polysulfides. The first model crosslinked disulfide system we synthesized was designed to maximize the ratio of S–S to the electrochemically inactive framework. The material contains a 1:1 ratio of S:C with a theoretical gravimetric capacity of 609 mAh g–1. Cells made with this crosslinked disulfide cathode material gain capacity through 100 cycles and have 98% capacity retention thereafter through 200 cycles, demonstrating promise for stable, long-term cycling. Coulombic efficiencies near 100% for every cycle, suggesting the suppression of polysulfide shuttle through molecular design. Further iterations of this crosslinked disulfide design aim to increase ionic and electronic conductivities to achieve higher gravimetric capacities that will lead these stable sulfur-based batteries closer to a commercially viable technology. Using crosslinked disulfides as cathode materials in liquid Li–S cells has not previously been explored in detail, so Raman spectroscopy provides an excellent handle to gain mechanistic insight into the conversion processes in these systems. Ex situ Raman confirms the proposed mechanism of disulfide bonds breaking to form a S–Li thiolate species upon discharge and reformation upon charge, and operando Raman provides more detailed understanding of the redox reactions occurring in the cell. Other characterization techniques, such as NMR and XPS provide structural information, in addition to SEM yielding macrostructural information, to piece together a detailed description of the disulfide behavior as a cathode material. Figure 1

An analogue of DPP, dithienylbenzodipyrrolidone (DTBDPD), was successfully synthesized. Several D–A copolymers, with different electron donating capability donor unit (fluorene, difluorene, dithienosilole, and dithienopyrrole) and DTBDPD acceptor, were prepared by means of Suzuki and Stille coupling reaction. The optical and electrochemical properties were demonstrated through UV–vis–NIR absorption and cyclic voltammetry (CV). All polymers showed near-infrared or even infrared absorption and deeper LUMO levels, as low as −3.80 eV.

Two new compounds containing tetrathiafulvalene (TTF) cations with extended and discrete anions based on Bi and I are reported. The compound (TTF)BiI

While recent improvements in the reported peak power conversion efficiency (PCE) of hybrid organic–inorganic perovskite solar cells have been truly astonishing, there are many fundamental questions about the electronic behavior of these materials. Here we have studied a set of electronic devices employing methylammonium lead iodide ((MA)PbI3) as the active material and conducted a series of temperature-dependent measurements. Field-effect transistor, capacitor, and photovoltaic cell measurements all reveal behavior consistent with substantial and strongly temperature-dependent polarization susceptibility in (MA)PbI3 at temporal and spatial scales that significantly impact functional behavior. The relative PCE of (MA)PbI3 photovoltaic cells is observed to reduce drastically with decreasing temperature, suggesting that such polarization effects could be a prerequisite for high-performance device operation.

Concentration matters: the self-assembly of title compound 1 evolves from well-defined ribbons to vesicles to baskets, upon simply decreasing the concentration of 1 in tetrahydrofuran. Electron microscopy revealed a unique self-assembled structure: baskets are formed by curved and self-wrapped nanometer-thin ribbons. The self-assembly of π-conjugated molecule 1 enables to construct nano/micro structures with desired optoelectronic properties.

High mobility ambipolor organic thin-film transistors based on an ultralow bandgap polymer are presented together with their morphological and optical properties. Hole and electron mobilities of this polymer are of 1.0 cm(2) V(-1) s(-1) and 0.7 cm(2) V(-1) s(-1), respectively. The inverter based on two identical ambipolar transistors exhibits a gain around 35.

Let's twist again: A “clean reaction” strategy based on thermally eliminating lactam bridges from a soluble acene precursor through a retro-Diels–Alder reaction gives a new, stable, green heptatwistacene (see structure). The molecule has a twist angle of 23.49°, is very stable even in air, and has an optical band gap of 1.82 eV.

A new dyad of fullerene/disperse-red, denoted as PCBDR, strongly absorbs visible light in the range of 400–600 nm. PCBDR showed advantages over PCBM in several aspects such as enhanced visible-light absorption, improved solubility, and the possibility to facilitate cascaded electron transfer. P3HT:PCBDR bulk heterojunction (BHJ) solar cells, nevertheless, so far have not outperformed P3HT:PCBM BHJ solar cells under similar conditions. Among factors that affect the efficiency of P3HT:PCBDR BHJ solar cells, the suppression of the interchain interaction of P3HT in the P3HT:PCBDR blend played a major role, presumably due to better interfacial miscibility between P3HT and PCBDR than that in blends of P3HT:PCBM. In contrast, benzoporphyrin (BP), due to its unique crystallinity, morphology, and nonsolubility, afforded a better control of the morphology and the interface of the p/n junctions. As a consequence, the performance of solar cells with BP/PCBDR as the active layer was comparable to that of BP/PCBM solar...

Condensations of polyhydroxyl monomers with terephthalaldehyde or isophthalaldehyde give the corresponding polyspiroacetals. The effects of various dialdehydes and multihydroxy monomers on the properties of the resulting polymer have been examined. Model compounds were synthesized by the condensation of multihydroxy monomers with benzaldehyde. The model compounds and polymers were characterized by Fourier transform infrared spectroscopy, nuclear magnetic resonance (NMR), thermogravimetric analysis and differential scanning calorimetry. The proposed polymer structure is supported by the solid-state CPMAS 13C NMR spectrum of the model compound. The synthesized polyspiroacetals are thermally stable, have a high degree of chemical stability and are soluble in hexafluoroisopropanol. Condensations of polyhydroxyl monomers with terephthalaldehyde and isophthalaldehyde in the presence of acid catalyst give polyspiroacetals. Model compounds have been synthesized by the condensation of multihydroxyl monomers with benzaldehyde. The effects of different dialdehyde and multihydroxy monomer on polymer properties have been examined. These polymers are found to be chemically and thermally stable.

We show that polybis(thienyl)thienodia-thiazolethiophene (PDDTT), a high-performance semiconducting polymer for photodetectors and field-effect transistors, has strong performance dependence on annealing temperature. An unprecedented increase of 3 orders of magnitude is observed in both transistor and photoconductive properties. XRD and AFM evidence points to increased ordering in PDDTT films with annealing. This correlation highlights the importance that order has in determining performance in PDDTT and has possible implications in the design of polymers.

The evaluation of the power conversion efficiency (PCE) of new materials for organic bulk heterojunction (BHJ) photovoltaics is difficult due to the large number of processing parameters possible. An efficient procedure to determine the optimum conditions for thermal treatment of polymer-based bulk heterojunction photovoltaic devices using in situ current-voltage measurements is presented. The performance of a new fullerene derivative, 1,9-dihydro-64,65-dihexyloxy-1,9-(methano[1,2] benzomethano)fullerene[60], in BHJ photovolatics with poly(3-hexylthiophene) (P3HT) was evaluated using this methodology. The device characteristics of BHJs obtained from the in situ method were found to be in good agreement with those from BHJs annealed using a conventional process. This fullerene has similar performance to 1-(3-methoxycarbonyl)propyl-1-phenyl-[6,6]-methano fullerene in BHJs with P3HT after thermal annealing. For devices with thickness of 70 nm, the short circuit current was 6.24 mA/cm2 with a fill factor of 0.53 and open circuit voltage of 0.65 V. The changes in the current-voltage measurements during thermal annealing suggest that the ordering process in P3HT dominates the improvement in power conversion efficiency. © 2011 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2012

A water/alcohol-soluble small molecule based on the commercially available pigment quinacridone is employed as an electron transport layer in organic photovoltaics. The quinacridone derivative is utilized in solution-processed bulk-heterojunction solar cells to improve primarily the fill factor of the devices, contributing to an upwards of 19% enhancement in the power conversion efficiency relative to the control devices with no electron transport layer. The facile synthesis of the quinacridone derivative coupled with the ease of device fabrication via solution processing provide a simple, yet effective means of improving the performance of existing organic photovoltaic cells.

Sodium N,N′-bis(3-sulfonylpropyl)quinacridone (Na+QPSO3–), tetraphenylphosphonium N,N′-bis(3-sulfonylpropyl)quinacridone (Ph4P+QPSO3–), sodium N,N′-bis(6-sulfonylhexyl)quinacridone (Na+QHSO3–), and tetraphenylphosphonium N,N′-bis(6-sulfonylhexyl)quinacridone (Ph4P+QHSO3–) are employed as solution-processable electron injection layers (EILs) in multilayer polymer light emitting diodes utilizing poly(2-methoxy-5-(2′-ethylhexyloxy)-1,4-phenylene vinylene) (MEH-PPV) as the emissive layer. The electron mobilities of these oligoelectrolytes are comparable with conjugated polyelectrolytes, but the synthesis is much simpler. The choice of counterion can be used to tune electron mobilities and optical properties. Increased aggregation in solution positively influences device performance, yielding devices that outperform those that use a barium cathode with no barrier for electron injection. These oligoelectrolyte EILs were also tested in devices utilizing a blue emissive small molecule. The ease of synthesis of th...

A successful synthesis of novel diimides, namely anthracene diimide containing six-membered imide rings, with potential application in organic electronics is reported. The single crystal of 5a exhibits a close interplanar spacing of 3.45 Å between molecules in a stack.

We report the formation of an electrochemically stable protective film for lithium electrodes by reacting lithium with tetraethoxysilane. Li/Li cell tests show that coated electrodes exhibit stable plating and stripping of Li at 1 mA/cm2 for 100 cycles without any change in cell impedance.

We report the synthesis and characterization of a novel, stable and blue heteroacene, 2-methyl-1,4,6,7,8,9-hexaphenylbenz(g)isoquinolin-3(2H)-one (BIQ 3). BIQ 3, with its relatively small π framework, has an absorption λ(max) at 620 nm, which is larger than that of pentacene (λ(max) = 582 nm), but BIQ 3 is more stable. The solutions of BIQ 3 are observed without any noticeable photobleaching on the order of days. In the solid state, it is very stable at ambient conditions and can be stored indefinitely. Owing to its pyridone end unit, BIQ 3 can display different resonance structures in different solvents (aprotic and protic) or Lewis acids to give different colors. The attractive stability exhibited by BIQ 3 is very desirable in organic semiconductor devices. Herein, we investigated a simple heterojunction photovoltaic device based on BIQ 3 as an electron donor and [6,6]-phenyl-C(61) butyric methyl ester as an electron acceptor. Our results show that this type of heteroacene could be a good candidate as a charge-transport material in organic semiconductor devices.

New conjugated oligomers, oligo(9,9-didodecylfluorene-bis-sulphurdiimide), consisting of 9,9-didodecylfluorene separated by -N=S=N- moieties, are reported. These oligomers are stable purple solids under ambient conditions with absorption covering a broad spectral window in the UV-vis range and a main broad peak centered at 555 nm with onset extending to 700 nm. These oligomers show an obviously longer conjugation length than its dimeric analogue, bis-9,9-didodecyl-fluorene-2-sulfurdiimide that shows a band-edge absorption centered at 484 nm with onset at 590 nm. The dimer and oligomers are soluble in a variety of organic solvents. Moreover, we found that the oligomer with an average repeating-unit number of six could significantly quench the photoluminescence (PL) of poly[2-methoxy-5-(2'-ethyl-hexyloxy)-1,4-phenylene vinylene] (MEH-PPV) or poly(3-hexylthiophene) (P3HT) in the solid state. More importantly, the composites of this oligomer with P3HT showed a nearly 10-fold enhancement of the photocurrent, compared with that of P3HT itself. In addition, the PL of this oligomer could be quenched by the presence of phenyl-C 61 -butyric acid methyl ester (PCBM) in toluene. These results suggest the presence of photoinduced charge transfer in composites of these oligomers blended with an electronic partner that either donates or accepts electrons.

Interfaces between phenylacetylene (PA) monolayers and two silicon surfaces, Si(111) and Si(100), are probed by X-ray photoelectron spectroscopy (XPS), ultraviolet photoelectron spectroscopy (UPS), and near-edge X-ray absorption fine structure (NEXAFS) spectroscopy, and the results are analyzed using ab initio molecular orbital calculations. The monolayer systems are prepared via the surface hydrosilylation reaction between PA and hydrogen-terminated silicon surfaces. The following spectral features are obtained for both of the PA-Si(111) and PA-Si(100) systems: a broad {pi}-{pi}* shakeup peak at 292 eV (XPS), a broad first ionization peak at 3.8 eV (UPS), and a low-energy C 1s {yields} {pi}* resonance peak at 284.3 eV (NEXAFS). These findings are ascribed to a styrene-like {pi}-conjugated molecular structure at the PA-Si interface by comparing the experimental data with theoretical analysis results. A conclusion is drawn that the vinyl group can keep its {pi}-conjugation character on the hydrogen-terminated Si(100) [H:Si(100)] surface composed of the dihydride (SiH{sub 2}) groups as well as on hydrogen-terminated Si(111) having the monohydride (SiH) group. The formation mechanism of the PA-Si(100) interface is investigated within cluster ab initio calculations, and the possible structure of the H:Si(100) surface is discussed based on available data.

The electrochemical synthesis of a new dithienylcyclopentadienone-derivative/3-methylthiopene copolymer was performed by cyclic voltammetry. The obtained material shows redox processes very close to those from the pristine DTCPD. A new redox process at -1.24 V, with a large anodic shift (0.51 V) related to the poly(3-methylthiophene) reduction, indicates the existence of a copolymer with a strong influence of the neighboring (n-doped) DTCPD comonomer. The new copolymer is electrochemically n-doped at more cathodic potentials than -750 mV and p-doped at more anodic potentials than 250 mV, with a bandgap of 1.0 eV. The cation's entrance in the film from the solution during n-doping and anion's entrance during p-doping for charge balance was checked by QCM. The reduction of the DTCPD part suffers a partial trapping of the negative charges that can be reoxidized only at high overpotentials (1 V related to the reduction potentials). After polarization of the material at any potential inside the band gap, subsequent p- or n-doping reactions performed by potential steps start by nucleation-relaxation kinetic control, followed by anodic or cathodic, respectively, chronoamperometric maxima. At the maxima, both reactions were checked to occur under chemical kinetic control, allowing the determination of the reaction orders for p- and n-doping processes.