Relating Structure to Properties in Non-Conjugated Pendant Electroactive Polymers.

Non-conjugated pendant electroactive polymers (NCPEPs) are an emerging class of polymers that offer the potential of combining the desirable optoelectronic properties of conjugated polymers with the superior synthetic methodologies and stability of traditional non-conjugated polymers. Despite an increasing number of studies focused on NCPEPs, particularly on understanding fundamental structure-property relationships, no attempts have been made to provide an overview on established relationships to date. This review showcases selected reports on NCPEP homopolymers and copolymers that demonstrate how optical, electronic, and physical properties of the polymers are affected by tuning of key structural variables such as the chemical structure of the polymer backbone, molecular weight, tacticity, spacer length, the nature of the pendant group, and in the case of copolymers the ratios between different comonomers and between individual polymer blocks. Correlation of structural features with improved π-stacking and enhanced charge carrier mobility serve as the primary figures of merit in evaluating impact on NCPEP properties. While this review is not intended to serve as a comprehensive summary of all reports on tuning of structural parameters in NCPEPs, it highlights relevant established structure-property relationships that can serve as a guideline for more targeted design of novel NCPEPs in the future.

High-Performance Intrinsically Stretchable Polymer Solar Cell with Record Efficiency and Stretchability Enabled by Thymine-Functionalized Terpolymer.

Designing new polymer semiconductors for intrinsically stretchable polymer solar cells (IS-PSCs) with high power conversion efficiency (PCE) and durability is critical for wearable electronics applications. Nearly all high-performance PSCs are constructed using fully conjugated polymer donors (PD) and small-molecule acceptors (SMA). However, a successful molecular design of PDs for high-performance and mechanically durable IS-PSCs without sacrificing conjugation has not been realized. In this study, we design a novel thymine side chain terminated 6,7-difluoro-quinoxaline (Q-Thy) monomer and synthesize a series of fully conjugated PDs (PM7-Thy5, PM7-Thy10, PM7-Thy20) featuring Q-Thy. The Q-Thy units capable of inducing dimerizable hydrogen bonding enable strong intermolecular PD assembly and highly efficient and mechanically robust PSCs. The PM7-Thy10:SMA blend demonstrates a combination of high PCE (>17%) in rigid devices and excellent stretchability (crack-onset value >13.5%). More importantly, PM7-Thy10-based IS-PSCs show an unprecedented combination of PCE (13.7%) and ultrahigh mechanical durability (maintaining 80% of initial PCE after 43% strain), illustrating the promising potential for commercialization in wearable applications.

Conjugated Polymers Via Direct Arylation Polymerization in Continuous Flow: Minimizing the Cost and Batch-to-Batch Variations for High-Throughput Energy Conversion.

Continuous flow methods are utilized in conjunction with direct arylation polymerization (DArP) for the scaled synthesis of the roll-to-roll compatible polymer, poly[(2,5-bis(2-hexyldecyloxy)phenylene)-alt-(4,7-di(thiophen-2-yl)-benzo[c][1,2,5]thiadiazole)] (PPDTBT). PPDTBT is based on simple, inexpensive, and scalable monomers using thienyl-flanked benzothiadiazole as the acceptor, which is the first ß-unprotected substrate to be used in continuous flow via DArP, enabling critical evaluation of the suitability of this emerging synthetic method for minimizing defects and for the scaled synthesis of high-performance materials. To demonstrate the usefulness of the method, DArP-prepared PPDTBT via continuous flow synthesis is employed for the preparation of indium tin oxide (ITO)-free and flexible roll-coated solar cells to achieve a power conversion efficiency of 3.5% for 1 cm2 devices, which is comparable to the performance of PPDTBT polymerized through Stille cross coupling. These efforts demonstrate the distinct advantages of the continuous flow protocol with DArP avoiding use of toxic tin chemicals, reducing the associated costs of polymer upscaling, and minimizing batch-to-batch variations for high-quality material.

Influence of ß-linkages on the morphology and performance of DArP P3HT-PC61BM solar cells.

Direct arylation polymerization (DArP) has emerged as a greener and more atom-efficient alternative to Stille polymerization. Despite the attractiveness of this method, DArP is known to produce ß-linkages in polymers, which have ß-protons available for activation. Here, we report the influence of the ß-defect content in DArP poly(3-hexylthiophene) (P3HT) on the performance of bulk-heterojunction solar cells and the morphology of pristine polymers and their blends with PC61BM in thin films and compare with Stille P3HT containing 0% ß-defects as a reference point. The optical and electrochemical properties as well as the hole mobilities of pristine polymers remain virtually the same when the amount of ß-defects is limited to 0.75% or lower, as evidenced by UV-visible absorption spectra, cyclic voltammetry and space-charge-limited current (SCLC) mobility measurements. However, an increase of ß-defect concentration to 1.41% significantly affects the oxidation onset, UV-visible absorption profile and hole mobility of P3HT. The key result of this study is that the photovoltaic performance of DArP P3HT with 0% ß-defects is remarkably close to that of Stille P3HT, whereas the performance of DArP P3HT with 0-0.75% ß-defects does not differ dramatically from that of Stille P3HT and could potentially be improved upon by individual optimization of the processing conditions.

Control of Properties through Hydrogen Bonding Interactions in Conjugated Polymers.

Molecular design is crucial for endowing conjugated polymers (CPs) with unique properties and enhanced electronic performance. Introducing Hydrogen-bonding (H-bonding) into CPs has been a broadly exploited, yet still emerging strategy capable of tuning a range of properties encompassing solubility, crystallinity, electronic properties, solid-state morphology, and stability, as well as mechanical properties and self-healing properties. Different H-bonding groups can be utilized to tailor CPs properties based on the applications of interest. This review provides an overview of classes of H-bonding CPs (assorted by the different H-bond functional groups), the synthetic methods to introduce the corresponding H-bond functional groups and the impact of H-bonding in CPs on corresponding electronic and materials properties. Recent advances in addressing the trade-off between electronic performance and mechanical durability are also highlighted. Furthermore, insights into future directions and prospects for H-bonded CPs are discussed.

Measuring the Electric Fields of Ions Captured in Crown Ethers.

Controlling reactivity with electric fields is a persistent challenge in chemistry. One approach is to tether ions at well-defined locations near a reactive center. To quantify fields arising from ions, we report crown ethers that capture metal cations as field sources and a covalently bound vibrational Stark shift probe as a field sensor. We use experiments and computations in both the gas and liquid phases to quantify the vibrational frequencies of the probe and estimate the electric fields from the captured ions. Cations, in general, blue shift the probe frequency, with effective fields estimated to vary in the range of ∼0.2-3 V/nm in the liquid phase. Comparison of the gas and liquid phase data provides insight into the effects of mutual polarization of the molecule and solvent and screening of the ion's field. These findings reveal the roles of charge, local screening, and geometry in the design of tailored electric fields.

Measuring Heat Dissipation and Entropic Potential in Battery Cathodes Made with Conjugated and Conventional Polymer Binders Using Operando Calorimetry.

This study explores the influence of electronic and ionic conductivities on the behavior of conjugated polymer binders through the measurement of entropic potential and heat generation in an operating lithium-ion battery. Specifically, the traditional poly(vinylidene fluoride) (PVDF) binder in LiNi0.8Co0.15Al0.05O2 (NCA) cathode electrodes was replaced with semiconducting polymer binders based on poly(3,4-propylenedioxythiophene). Two conjugated polymers were explored: one is a homopolymer with all aliphatic side chains, and the other is a copolymer with both aliphatic and ethylene oxide side chains. We have shown previously that both polymers have high electronic conductivity in the potential range of NCA redox, but the copolymer has a higher ionic conductivity and a slightly lower electronic conductivity. Entropic potential measurements during battery cycling revealed consistent trends during delithiation for all of the binders, indicating that the binders did not modify the expected NCA solid solution deintercalation process. The entropic signature of polymer doping to form the conductive state could be clearly observed at potentials below NCA oxidation, however. Operando isothermal calorimetric measurements showed that the conductive binders resulted in less Joule heating compared to PVDF and that the net electrical energy was entirely dissipated as heat. In a comparison of the two conjugated polymer binders, the heat dissipation was lower for the homopolymer binder at lower C-rates, suggesting that electronic conductivity rather than ionic conductivity was the most important for reducing Joule heating at lower rates, but that ionic conductivity became more important at higher rates.

Origin of the tunable open-circuit voltage in ternary blend bulk heterojunction organic solar cells.

Ternary blend bulk heterojunction organic solar cells comprising either a polythiophene donor and two fullerene acceptors or two polythiophene donors and a fullerene acceptor are shown to have unique electronic properties. Measurements of the photocurrent spectral response and the open-circuit voltage show that the HOMO and LUMO levels change continuously with composition in the respective two-component acceptor or donor pair, consistent with the formation of an organic alloy. However, optical absorption of the exciton states retains the individual molecular properties of the two materials across the blend composition. This difference is attributed to the highly localized molecular nature of the exciton and the more delocalized intermolecular nature of electrons and holes that reflect the average composition of the alloy. As established here, the combination of molecular excitations that can harvest a wide range of photon energies and electronic alloy states that can adjust the open-circuit voltage provides the underlying basis of ternary blends as a platform for highly efficient next-generation organic solar cells.

Influence of selenophene on the properties of semi-random polymers and their blends with PC61BM.

In an effort to broaden the absorption of conjugated polymers, atomistic bandgap control was applied to the semi-random polymer architecture. Here, we report the physical properties of semi-random polyselenophenes as compared to analogous polythiophenes. In order to examine the effect of the selenium heteroatom on the optical properties of the polymers, UV-vis spectra were studied and it was found that all polyselenophenes exhibit lower bandgaps and higher absorption coefficients in thin films. Further, differential scanning calorimetry and grazing incidence x-ray diffraction results indicate that semi-random polyselenophenes are semicrystalline polymers and their (100) interchain distances are shorter than in the case of semi-random polythiophenes, which may be responsible for higher absorption coefficients. To probe the effect of the selenium heteroatom on the nano-organization of these polymers and their blends with PC61BM, thin films were studied by transmission electron microscopy (TEM). The TEM images show a segregation between more densely packed areas from less densely packed areas in the pristine polymer films, which is more pronounced for polyselenophenes than for polythiophenes. The blends of polyselenophenes with PC61BM do not show the well-defined segregation observed for the polythiophene analogues. However, the broadened and extended absorption of semi-random polyselenophenes translates into an extended photocurrent response in the photovoltaic devices, as evidenced by external quantum efficiency measurements.

Room Temperature Synthesis of a Well-Defined Conjugated Polymer Using Direct Arylation Polymerization (DArP).

While a major improvement to the sustainability of conjugated polymer synthesis, traditional direct arylation polymerization (DArP) still requires high temperatures (typically >100 °C), necessitating a significant energy input requirement. Performing DArP at reduced or ambient temperatures would represent an improvement to the sustainability of the reaction. Here we describe the first report of a well-defined conjugated polymer synthesized by DArP at room temperature. Previous efforts toward room temperature DArP relied on the use of a near-stoichiometric silver reagent, an expensive coinage metal, which makes the reaction less cost-effective and sustainable. Here, room temperature polymerizations of 3,4-ethylenedioxythiophene (EDOT) and 9,9-dioctyl-2,7-diiodofluorene were optimized and provided molar mass (Mn) up to 11 kg/mol PEDOTF, and performing the reaction at the standard ambient temperature of 25 °C provided Mn up to 15 kg/mol. Model studies using other C-H monomers of varying electron density copolymerized with 9,9-dioctyl-2,7-diiodofluorene provided insight into the scope of the room temperature polymerization, suggesting that performing room temperature DArP is highly dependent on the electron richness of the C-H monomer.

Synthesis of Block Copolymers Containing Stereoregular Pendant Electroactive Blocks.

The stereoregular nonconjugated pendant electroactive polymer (NCPEP) poly((N-carbazolylethylthio) propyl methacrylate) (PCzETPMA) has recently shown charge carrier mobilities that are on par with conjugated polymers. Here, we increased the complexity of the architecture for this NCPEP by introducing a polystyrene (PS) block via an anionic, living polymerization yielding a family of PS-b-PCzETPMA block copolymers as the first examples of NCPEP-block-copolymers with controlled stereoregularity of the NCPEP-blocks. Through this methodology we were able to control the molar masses, PS to PCzETPMA block ratios, and tacticities of the PCzETPMA-blocks. We found all three parameters to significantly impact the hole mobilities (µh) of the resulting copolymers, which increased with higher molar masses, longer PCzETPMA-blocks, and higher isotacticity of the PCzETPMA-block, giving the best µh of 2.33 × 10-5 cm2/V·s after annealing at 150 °C for the highest molar mass copolymer with a dominant isotactic PCzETPMA-block. This work is the first reported synthesis of a block copolymer bearing a NCPEP-block with a controlled tacticity and demonstrates that such complex polymer architectures can be realized with NCPEPs while maintaining control over their stereoregularity and without significantly suppressing the hole mobility in the resulting copolymers.

Distinguishing between the Electrostatic Effects and Explicit Ion Interactions in a Stark Probe.

Vibrational Stark probes are incisive tools for measuring local electric fields in a wide range of chemical environments. The interpretation of the frequency shift often gets complicated due to the specific interactions of the probe, such as hydrogen bonding and Lewis bonding. Therefore, it is important to distinguish between the pure electrostatic response and the response due to such specific interactions. Here we report a molecular system that is sensitive to both the Stark effect from a single ion and the explicit Lewis bonding of ions with the probe. The molecule consists of a crown ether with an appended benzonitrile. The crown captures cations of various charges, and the electric field from the ions is sensed by the benzonitrile probe. Additionally, the lone pair of the benzonitrile can engage in Lewis interactions with some of the ions by donating partial charge density to the ions. Our system exhibits both of these effects and therefore is a suitable test bed for distinguishing between the pure electrostatic and the Lewis interactions. Our computational results show that the electrostatic influence of the ion is operative at large distances, while the Lewis interaction becomes important only within distances that permit orbital overlap. Our results may be useful for using the nitrile probe for measuring electrostatic and coordination effects in complex ionic environments such as the electrode-electrolyte interfaces.

Compositional dependence of the open-circuit voltage in ternary blend bulk heterojunction solar cells based on two donor polymers.

Ternary blend bulk heterojunction (BHJ) solar cells containing as donor polymers two P3HT analogues, high-band-gap poly(3-hexylthiophene-co-3-(2-ethylhexyl)thiophene) (P3HT(75)-co-EHT(25)) and low-band-gap poly(3-hexylthiophene-thiophene-diketopyrrolopyrrole) (P3HTT-DPP-10%), with phenyl-C(61)-butyric acid methyl ester (PC(61)BM) as an acceptor were studied. When the ratio of the three components was varied, the open-circuit voltage (V(oc)) increased as the amount of P3HT(75)-co-EHT(25) increased. The dependence of V(oc) on the polymer composition for the ternary blend regime was linear when the overall polymer:fullerene ratio was optimized for each polymer:polymer ratio. Also, the short-circuit current densities (J(sc)) for the ternary blends were bettter than those of the binary blends because of complementary polymer absorption, as verified using external quantum efficiency measurements. High fill factors (FF) (>0.59) were achieved in all cases and are attributed to high charge-carrier mobilities in the ternary blends. As a result of the intermediate V(oc), increased J(sc) and high FF, the ternary blend BHJ solar cells showed power conversion efficiencies of up to 5.51%, exceeding those of the corresponding binary blends (3.16 and 5.07%). Importantly, this work shows that upon optimization of the overall polymer:fullerene ratio at each polymer:polymer ratio, high FF, regular variations in V(oc), and enhanced J(sc) are possible throughout the ternary blend composition regime. This adds to the growing evidence that the use of ternary blends is a general and effective strategy for producing efficient organic photovoltaics manufactured in a single active-layer processing step.

Recycling Heterogenous Catalysts for Multi-Batch Conjugated Polymer Synthesis via Direct Arylation Polymerization.

Despite the inherent sustainability direct arylation polymerization (DArP) offers through a C-H activation pathway, the use of expensive homogeneous Pd catalysts remains problematic for large-scale conjugated polymer (CP) synthesis. Herein, the first report on the recycling of heterogeneous catalysts for CP synthesis using DArP is presented. We found SiliaCat Pd-DPP to be a highly efficient and recyclable catalyst for multi-batch CP synthesis providing CPs with molecular weights (Mn) up to 82 kg/mol even after being recycled three times. Batch-to-batch variations were further optimized to afford up to five batches of polymers with a Mn of 25 ± 2.5 kg/mol without structural disparity. Significantly, this work discloses among the most sustainable CP synthesis protocols to date and presents the critical concept of catalyst-recycling to the important field of organic semiconducting polymers, which potentially enables access to truly low-cost flow chemistry for industrial-scale CP synthesis.

Efficient ternary blend bulk heterojunction solar cells with tunable open-circuit voltage.

To explore the potential of ternary blend bulk heterojunction (BHJ) photovoltaics as a general platform for increasing the attainable performance of organic solar cells, a model system based on poly(3-hexylthiophene) (P3HT) as the donor and two soluble fullerene acceptors, phenyl-C(61)-butyric acid methyl ester (PC(61)BM) and indene-C(60) bisadduct (ICBA), was examined. In all of the solar cells, the overall ratio of polymer to fullerene was maintained at 1:1, while the composition of the fullerene component (PC(61)BM:ICBA ratio) was varied. Photovoltaic devices showed high short-circuit current densities (J(sc)) and fill factors (FF) (>0.57) at all fullerene ratios, while the open-circuit voltage (V(oc)) was found to vary from 0.61 to 0.84 V as the fraction of ICBA was increased. These results indicate that the V(oc) in ternary blend BHJ solar cells is not limited to the smallest V(oc) of the corresponding binary blend solar cells but can be varied between the extreme V(oc) values without significant effect on the J(sc) or FF. By extension, this result suggests that ternary blends provide a potentially effective route toward maximizing the attainable J(sc)V(oc) product (which is directly proportional to the solar cell efficiency) in BHJ solar cells and that with judicious selection of donor and acceptor components, solar cells with efficiencies exceeding the theoretical limits for binary blend solar cells could be possible without sacrificing the simplicity of a single active-layer processing step.

Influence of Alkyl Chain Spacer Length on the Charge Carrier Mobility of Isotactic Poly(N-carbazolylalkyl acrylates).

In the search for semiconducting polymer alternatives to conjugated polymers, stereoregular nonconjugated pendant electroactive polymers (NCPEPs) have recently shown competitive hole mobilities with conjugated polymers and a dramatic increase in mobility relative to atactic analogues. Here we investigate one of the key structural variables of NCPEPs: the flexible alkyl spacer that separates the electroactive pendant from the backbone. We investigate a straightforward postpolymerization functionalization synthetic method to synthesize such polymers with high isotacticity using poly(N-carbazolylalkyl acrylate) as a model system, where the alkyl chain spacer in the NCPEPs is varied from 2 to 12 carbons. We observed that the hole mobility increased from the two-carbon spacer, resulting in the highest mobility upon thermal annealing with a four-carbon spacer for 75% isotactic polymers and with a six-carbon spacer for 87% isotactic polymers. As such, we have demonstrated an important role of the spacer chain in influencing mobility. For all spacer lengths, higher mobilities were measured with the more isotactic polymer. While physical characterization of the largely amorphous polymers yielded little insight into the structure-function relationships, DFT and MD simulations indicated helical structures for the polymers where intermolecular short-range π-stacking is observed and is affected by spacer chain length. This work demonstrates that both the degree of stereoregularity and the spacer chain length play a role in determining the hole mobility in NCPEPs.

p-Cymene: A Sustainable Solvent that is Highly Compatible with Direct Arylation Polymerization (DArP).

For over a decade, Direct Arylation Polymerization (DArP) has been demonstrated to be an eco-friendly, facile, and low-cost alternative to conventional methodologies such as Stille polymerization for conjugated polymer synthesis. By accessing through a C-H activation pathway, DArP offers a reduction of synthetic steps while eliminating the generation of stoichiometric, highly toxic organotin byproducts. However, as the major component in these reactions, the solvents most prevalently employed for DArP are hazardous and produced from unsustainable sources, such as dimethylacetamide (DMA), tetrahydrofuran (THF), and toluene. Although the use of sustainable alternative solvents such as 2-MeTHF and cyclopentyl methyl ether (CPME) has recently emerged, drawbacks of ethereal solvents include the need for a pressurized reaction setup as well as potential peroxide formation. While aromatic solvents are superior in solubilizing conjugated polymers, very little has been done in searching for more sustainable, benign alternatives for this class of solvent. Herein, we report the application of a sustainable, naturally sourced, high-boiling aromatic solvent, p-cymene, to DArP for the first time. p-Cymene was found to display excellent solubilizing ability in the synthesis of a broad scope of alternating copolymers with Mn up to 51.3 kg/mol and yields up to 96.2%, outperforming those prepared using CPME and toluene. Structural analysis revealed the exclusion of defects in these polymers prepared using p-cymene as the solvent which, in the case of a 2,2'-bithiophene monomer, is challenging to access through the use of conventional solvents for DArP, such as DMA and toluene.

Contrasting the Charge Carrier Mobility of Isotactic, Syndiotactic, and Atactic Poly((N-carbazolylethylthio)propyl methacrylate).

Isotactic nonconjugated pendant electroactive polymers (NCPEPs) have recently shown potential to achieve comparable charge carrier mobilities with conjugated polymers. Here we report the broader influence of tacticity in NCPEPs, using poly((N-carbazolylethylthio)propyl methacrylate) (PCzETPMA) as a model polymer. We utilized the thiol-ene reaction as an efficient postpolymerization functionalization method to achieve pendant polymers with high isotacticity and syndiotacticity. We found that a stereoregular isotactic polymer showed ∼100 times increased hole mobility (µh) as compared to both atactic and low molecular weight syndiotactic PCzETPMA, achieving µh of 2.19 × 10-4 cm2 V-1 s-1 after annealing at 120 °C. High molecular weight syndiotactic PCzETPMA gave ∼10 times higher µh than its atactic counterpart, comparable to isotactic PCzETPMA after annealing at 150 °C. Importantly, high molecular weight syndiotactic PCzETPMA showed a dramatic increase in µh to 1.82 × 10-3 cm2 V-1 s-1 when measured after annealing at 210 °C, which surpassed the well-known conjugated polymer poly(3-hexylthiophene) (P3HT) (µh = 4.51 × 10-4 cm2 V-1 s-1). MD simulations indicated short-range π-π stacked ordering in the case of stereoregular isotactic and syndiotactic polymers. This work is the first report of charge carrier mobilities in syndiotactic NCPEPs and demonstrates that the tacticity, annealing conditions, and molecular weight of NCPEPs can strongly affect µh.

An Efficient Precatalyst Approach for the Synthesis of Thiazole-Containing Conjugated Polymers via Cu-Catalyzed Direct Arylation Polymerization (Cu-DArP).

Over the past decade, direct arylation polymerization (DArP) has emerged as a facile and sustainable methodology for the synthesis of conjugated polymers. Recently, we developed Cu-catalyzed DArP (Cu-DArP) as a low-cost, Pd-free synthetic pathway, which enables conjugated polymers to be synthesized with high molecular weights and minimization of defects. However, the lack of study on the use of Cu-precatalysts in small-molecule direct arylation poses significant limitations for Cu-DArP to potentially overtake conventional Pd-catalyzed methodology, such as the low solubility and stability of the previously employed CuI. Therefore, in this report, we decide to explore the utility of a well-defined, easy-to-prepare, highly soluble, and stable precatalyst, Cu(phen)(PPh3)Br, as an alternative to the CuI, 1,10-phenanthroline catalytic system previously used for Cu-DArP. Herein, we report a drastic improvement of Cu-DArP methodology for the synthesis of 5,5'-bithiazole (5-BTz)-based conjugated polymers enabled by an efficient precatalyst approach, affording polymers with good Mn (up to 16.5 kDa) and excellent yields (up to 79%). 1H NMR studies reveal the exclusion of homocoupling defects, which further verifies the excellent stability of Cu(phen)(PPh3)Br compared to CuI. Furthermore, we were able to decrease the catalyst loading from 15 mol % to only 5 mol % (Mn of 11.8 kDa, 64% yield), which is unprecedented when aryl bromides are employed for Cu-DArP. Significantly, 5-BTz was shown to be inactive under various of Pd-DArP conditions, which demonstrates the high compatibility of Cu-DArP as the only pathway for the C-H activation of the 5-BTz unit and a clear case demonstrating an advantage of Cu-DArP relative to Pd-DArP.

All-polymer photovoltaic devices of poly(3-(4-n-octyl)-phenylthiophene) from Grignard Metathesis (GRIM) polymerization.

The synthesis of poly[3-(4-n-octyl)-phenylthiophene] (POPT) from Grignard Metathesis (GRIM) is reported. GRIM POPT is found to have favorable electronic, optical, and processing properties for organic photovoltaics (OPVs). Space-charge limited current and field effect transistor measurements for POPT yielded hole mobilities of 1 x 10(-4) cm(2)/(V s) and 0.05 cm(2)/(V s), respectively. Spincasting GRIM POPT from chlorobenzene yields a thin film with a 1.8 eV band gap, and PC(61)BM:POPT bulk heterojection devices provide a peak performance of 3.1%. Additionally, an efficiency of 2.0% is achieved in an all-polymer, bilayer OPV using poly[2-methoxy-5-(2'-ethylhexyloxy)-1,4-(1-cyanovinylene)phenylene] (CNPPV) as an acceptor. This state-of-the-art all-polymer device is analyzed in comparison to the analogous poly(3-hexylthiophene) (P3HT)/CNPPV device. Counter to expectations based on more favorable energy level alignment, greater active layer light absorption, and similar hole mobility, P3HT/CNPPV devices perform less well than POPT/CNPPV devices with a peak efficiency of 0.93%.