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The Effect of Replacing Alkyl Side Chains with Triethylene Glycols on Photovoltaic Properties of Easily Accessible Fluorene-based Non-fullerene Molecular Acceptors: Improve or Deteriorate?

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Abstract

Hydrophilic oligo (ethylene glycol) (OEG) side chains are more flexible than alkyl chains and can facilitate the π - π stacking of conjugated polymer backbones, which has been proven to be a key structural feature leading to better device performance in polymer: fullerene blend polymer solar cells (PSCs). So far, little has been known about the influence of OEG side chains on the performance of non-fullerene acceptors in polymer:non-fullerene acceptor blends. Based on an easily accessible conjugated backbone of dicyanomethylene indanone-thiophene-fluorene-thiophene-dicyanometnylene indanone (DICTF), two non-fullerene molecular acceptors were synthesized with decyl (DICTF-C10) and triethylene glycol monoether (DICTF-TEG) side chains to blend with the polymer donor of PTB7-Th for PSCs. Replacing the decyl side chains with the TEGs on DICTF does improve the π - π stacking between the conjugated backbones as expected. For DICTF-TEG, nevertheless, forming the BHJ blend with the PTB7-Th donor leads to unfavorable film morphology structure of the active blend and deteriorated device performance with much lower PCE of 3.09% compared to the blend of PTB7-Th:DICTF-C10 with the maximum PCE of 6.93% at optimized condition. It is found that charge generation, transport and recombination within the PSC devices of the two acceptors were greatly impacted by introducing TEG side chains instead of alkyls into the conjugated backbone of DICTF. This comparative study on understanding the side chain effect on device performance allows the establishment of guidance on molecular engineering of non-fullerene molecular acceptors to obtain high performance PSCs.

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... The I − compensate slightly for the electrostatic-induced broadening, leading to a reduction of the 0.28 and 0.35 eV standard deviations of the S − distributions to the 0.22 and 0.30 eV standard deviations of the P − and gas-phase contributions.According to the present findings, PTEG-1 is predicted to decrease the open-circuit voltage (V OC ), given the same blend, due to increased electrostatic disorder. Such a decrease in V OC was previously reported upon EG-functionalization of polymers 7 and nonfullerene acceptors,53 and upon cyano-functionalization 54 of polymers, the latter being another way of introducing permanent dipole moments in organic semiconductors. 14 Broadening of charge carrier energy levels can also lead to lower mobilities.54 ...
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The field of conjugated polymers has expanded in the last years considerably and impressive performance, both in field effect transistors and photovoltaic devices has been achieved. After the initial emphasis on improving the performance, more emphasis is recently given to fundamental studies on structure formation. Therefore, this review concentrates on systematic correlation studies of structure formation in solution, in bulk and thin films as well as in photovoltaic blends of donor-type π-conjugated polymers. The main focus is on the correlation of structure, morphology and molecular chain orientation as a function of macromolecular properties such as molecular weight, dispersity, non-covalent intramolecular and intermolecular interactions, solvent interactions and innovative processing techniques. The tools applied for elucidating fundamental information of structure formation and orientation mainly consist of optical spectroscopy and scattering techniques (SAXS/WAXS/GIWAXS). Since the field of conjugated polymers is very vast in terms of chemical structural diversity, only selected examples of donor polymers are covered here and the emerging class of n-type conjugated polymers are not included. The focus is not on the structural variation or their performance in solar cells or transistors in terms of record efficiencies, but on the systematic studies leading to a structure-property correlation in donor polymers.
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Over the past decades, fullerene derivatives have become the most successful electron acceptors in the organic solar cells (OSCs) and have achieved great progress, showing power conversion efficiencies (PCEs) of over 11%. However, fullerenes have some drawbacks such as weak absorption, limited energy-level tunability, and morphological instability. In addition, fullerene-based OSCs usually suffer from large energy losses of over 0.7 eV, which limits further improvement of the PCE. Recently, non-fullerene small molecules have emerged as promising electron acceptors in OSCs. Their highly tunable absorption spectra and molecular energy levels have enabled the fine optimization of the resulting devices, and the highest PCE has surpassed 12%. Furthermore, several studies have shown that OSCs based on small molecule acceptors (SMA) have very efficient charge generation and transport efficiency at relatively low energy losses below 0.6 eV, suggesting great potential for the further improvement of OSCs. In this focus review, we analyze the challenges and potential of SMA-based OSCs and discuss the molecular design strategy for highly efficient SMAs.
Article
Increasing interests have been devoted to developing high-performance all polymer solar cells (all-PSCs) owing to their specific advantages in light absorption and long-term stability. In this work, we systematically investigated the synergistic effects of processing solvents and molecular weight on the photovoltaic performance of all-PSCs, which consist of an n-type of polymer N2200, and a p-type of wide bandgap polymer PTzBI that are made up of benzodithiophene and imide functionalized benzotriazole unit. It is noted that increasing the molecular weight of N2200 can simultaneously enhance the exciton generation and dissociation, reduce the bimolecular recombination, and facilitate charge extraction. The films processed with environmentally friendly solvent 2-methyl-tetrahydrofuran (MeTHF) exhibits more favourable film morphology than those processed from commonly used halogenated solvents. The all-PSC consisting of the high molecular weight N2200 and PTzBI processed with environmentally friendly solvent MeTHF presents a remarkable power conversion efficiency of 9.16%, which is the highest value so far observed for all-PSCs. Of particular interest is that the PCE remains 6.37% with the active layer thickness of 230 nm. These obervations imply the great promise of the developed all-PSCs for practical applications toward high throughput roll-to-roll technology.
Article
The past decade has witnessed significant advances in the field of organic solar cells (OSCs). Ongoing improvements in the power conversion efficiency of OSCs have been achieved, which were mainly attributed to the design and synthesis of novel conjugated polymers with different architectures and functional moieties. Among various conjugated polymers, the development of wide-bandgap (WBG) polymers has received less attention than that of low-bandgap and medium-bandgap polymers. Here, we briefly summarize recent advances in WBG polymers and their applications in organic photovoltaic (PV) devices, such as tandem, ternary, and non-fullerene solar cells. Addtionally, we also dissuss the application of high open-circuit voltage tandem solar cells in PV-driven electrochemical water dissociation. We mainly focus on the molecular design strategies, the structure-property correlations, and the photovoltaic performance of these WBG polymers. Finally, we extract empirical regularities and provide invigorating perspectives on the future development of WBG photovoltaic materials.
Article
Power conversion efficiency (PCE) has surpassed 10% for single junction organic solar cells (OSCs) mainly through the design and synthesis of novel donor materials, the optimization of film morphology and the evolution of the devices. However, the development of novel acceptor materials is relatively sluggish compared with the donor compounds. Nowadays, fullerene derivatives, such as PC61BM and PC71BM, are still the dominant acceptors due to their superior charge transporting properties. Unfortunately, these two acceptors suffer from some intrinsic shortcomings such as limited absorption, difficult functionalization, and high production cost. Therefore, developing novel non-fullerene acceptors that can overcome the above-mentioned disadvantages is highly desirable. As a matter of fact, research on non-fullerene acceptors has made considerable progress in the last two years and a highest PCE of around 12% has been achieved. In this review, we will summarize recent research progress in non-fullerene small molecule acceptors and compare these molecules' performances in OSCs employing the same donor materials. Moreover, the acceptors with excellent photovoltaic performance are highlighted and the reasons are elaborated. Finally, the implications and the challenges are proposed.
Article
The device efficiency of polymer:fullerene bulk heterojunction solar cells has recently surpassed 11%, as a result of synergistic efforts among chemists, physicists, and engineers. Since polymers are unequivocally the "heart" of this emerging technology, their design and synthesis have consistently played the key role in the device efficiency enhancement. In this article, the first focus is a discussion on molecular engineering (e.g., backbone, side chains, and substituents), then the discussion moves on to polymer engineering (e.g., molecular weight). Examples are primarily selected from the authors contributions; yet other significant discoveries/developments are also included to put the discussion in a broader context. Given that the synthesis, morphology, and device physics are inherently related in explaining the measured device output parameters (Jsc , Voc and FF), we will attempt to apply an integrated and comprehensive approach (synthesis, morphology, and device physics) to elucidate the fundamental, underlying principles that govern the device characteristics, in particular, in the context of disclosing structure-property correlations. Such correlations are crucial to the design and synthesis of next generation materials to further improve the device efficiency.
Article
All-polymer solar cells (all-PSCs), consisting of conjugated polymers as both electron donor (PD) and acceptor (PA), have recently attracted great attention. Remarkable progress has been achieved during the past few years, with power conversion efficiencies (PCEs) now approaching 8%. In this Account, we first discuss the major advantages of all-PSCs over fullerene-polymer solar cells (fullerene-PSCs): (i) high light absorption and chemical tunability of PA, which affords simultaneous enhancement of both the short-circuit current density (JSC) and the open-circuit voltage (VOC), and (ii) superior long-term stability (in particular, thermal and mechanical stability) of all-PSCs due to entangled long PA chains. In the second part of this Account, we discuss the device operation mechanism of all-PSCs and recognize the major challenges that need to be addressed in optimizing the performance of all-PSCs. The major difference between all-PSCs and fullerene-PSCs originates from the molecular structures and interactions, i.e., the electron transport ability in all-PSCs is significantly affected by the packing geometry of two-dimensional PA chains relative to the electrodes (e.g., face-on or edge-on orientation), whereas spherically shaped fullerene acceptors can facilitate isotropic electron transport properties in fullerene-PSCs. Moreover, the crystalline packing structures of PD and PA at the PD-PA interface greatly affect their free charge carrier generation efficiencies. The design of PA polymers (e.g., main backbone, side chain, and molecular weight) should therefore take account of optimizing three major aspects in all-PSCs: (1) the electron transport ability of PA, (2) the molecular packing structure and orientation of PA, and (3) the blend morphology. First, control of the backbone and side-chain structures, as well as the molecular weight, is critical for generating strong intermolecular assembly of PA and its network, thus enabling high electron transport ability of PA comparable to that of fullerenes. Second, the molecular orientation of anisotropically structured PA should be favorably controlled in order to achieve efficient charge transport as well as charge transfer at the PD-PA interface. For instance, face-to-face stacking between PD and PA at the interface is desired for efficient free charge carrier generation because misoriented chains often cause an additional energy barrier for overcoming the binding energy of the charge transfer state. Third, large-scale phase separation often occurs in all-PSCs because of the significantly reduced entropic contribution by two macromolecular chains of PD and PA that energetically disfavors mixing. In this Account, we review the recent progress toward overcoming each recognized challenge and intend to provide guidelines for the future design of PA. We believe that by optimization of the parameters discussed above the PCE values of all-PSCs will surpass the 10% level in the near future and that all-PSCs are promising candidates for the successful realization of flexible and portable power generators.
Article
With the rapid development of polymer solar cells (PSCs), the manufacture of high-performance large area PSC modules is becoming a critical issue in commercial applications. However, most of the reported light absorption materials and interfa-cial materials are quite thickness sensitive, with optimal thicknesses of around 100 nm and 5 nm, respectively. The thickness need to be precisely controlled, otherwise, a small variation in thickness can often lead to a sharp decrease in device perfor-mance, especially for interfacial materials. This increases the difficulty of apply these materials in the production of large area PSCs. To avoid the shortcomings of thickness-sensitive materials and achieve high-performance large area PSC mod-ules, we designed and synthesized a series of high mobility donor materials and cathode interfacial materials. These materi-als exhibited excellent device performance at their optimal thicknesses and maintained high performance even with large thickness variations, thus providing a solution to the bottleneck problem in manufacturing PSC modules and enhancing the device reproducibility. We also developed a simple and efficient approach for achieving a large area cathode interlayer with controlled film composition, uniformity, and thickness at the nanometer-scale using an electrostatic layer-by-layer self-assembly (eLbL) process. The eLbL films exhibited excellent cathode modification ability and can be integrated into the current large area device processing techniques. Thus, our approaches from both material design to device engineering pro-vide new solutions for preparing high-performance large area PSC modules.
Article
The past two decades of vigorous interdisciplinary approaches has seen tremendous breakthroughs in both scientific and technological developments of bulk-heterojunction organic solar cells (OSCs) based on nanocomposites of π-conjugated organic semiconductors. Because of their unique functionalities, the OSC field is expected to enable innovative photovoltaic applications that can be difficult to achieve using traditional inorganic solar cells: OSCs are printable, portable, wearable, disposable, biocompatible, and attachable to curved surfaces. The ultimate objective of this field is to develop cost-effective, stable, and high-performance photovoltaic modules fabricated on large-area flexible plastic substrates via high-volume/throughput roll-to-roll printing processing and thus achieve the practical implementation of OSCs. Recently, intensive research efforts into the development of organic materials, processing techniques, interface engineering, and device architectures have led to a remarkable improvement in power conversion efficiencies, exceeding 11%, which has finally brought OSCs close to commercialization. Current research interests are expanding from academic to industrial viewpoints to improve device stability and compatibility with large-scale printing processes, which must be addressed to realize viable applications. Here, both academic and industrial issues are reviewed by highlighting historically monumental research results and recent state-of-the-art progress in OSCs. Moreover, perspectives on five core technologies that affect the realization of the practical use of OSCs are presented, including device efficiency, device stability, flexible and transparent electrodes, module designs, and printing techniques.
Article
A great advantage of conjugated polymers is the solution processability with low cost. As conjugated polymers typically have flexible alkyl side chains for solubility in organic solvents, J. Liu, L. Wang, and co-workers report in their Communication (DOI: 10.1002/anie.201602775) soluble conjugated polymers bearing novel side chains, branched oligo(ethylene glycol). These polymers can be used in solution-processed polymer solar cells with high efficiency and near-IR response.
Article
A simple small molecule acceptor named DICTF, with fluorene as the central block and 2-(2,3-dihydro-3-oxo-1H-inden-1-ylidene)propanedinitrile as the end-capping groups, has been designed for fullerene-free organic solar cells. The new molecule was synthesized from widely available and inexpensive commercial materials in only three steps with a high overall yield of ∼60%. Fullerene-free organic solar cells with DICTF as the acceptor material provide a high PCE of 7.93%.
Article
Conjugated polymers are essential for solution-processable organic opto-electronic devices. In contrast to the great efforts on developing new conjugated polymer backbones, research on developing side chains is rare. Herein, we report branched oligo(ethylene glycol) (OEG) as side chains of conjugated polymers. Compared with typical alkyl side chains, branched OEG side chains endowed the resulting conjugated polymers with a smaller π-π stacking distance, higher hole mobility, smaller optical band gap, higher dielectric constant, and larger surface energy. Moreover, the conjugated polymers with branched OEG side chains exhibited outstanding photovoltaic performance in polymer solar cells. A power conversion efficiency of 5.37 % with near-infrared photoresponse was demonstrated and the device performance could be insensitive to the active layer thickness.
Chapter
This chapter focuses on the synthesis, design concepts and photovoltaic performance of fullerene-based electron acceptors used in solution processed organic solar cells. Excellent fullerene acceptors such as PCBM, SIMEF, 1,4-di(aryl)fullerenes, diphenylmethanofullerenes, fulleropyrrolidines, ICBA, methano-indene-fullerenes are introduced from a synthetic chemistry viewpoint in addition to fullerene chemistry background being offered, which should benefit a wide range of organic solar cell research.
Chapter
Conventional inorganic solar cells can achieve high efficiencies, but are complicated and costly to produce. The desirability of a lower cost is driving the development of several third-generation solar cell technologies. Of these, the polymer solar cell (PSC) is particularly cheap to produce, as polymer solar panels can be fabricated using extremely high throughput roll-to-roll printing methods similar to those used to print newspapers. State-of-the-art PSCs consist of a blend film of a polymer and a fullerene derivative, which function as an electron-donor and an electron-acceptor, respectively. Although this type of polymer:fullerene solar cell achieves an impressive efficiency (9.2% for single-junction cells), the fullerene acceptors have several disadvantages. In the hope of addressing these issues, PSCs based on non-fullerene acceptors have been developed. In general, there are two alternatives for the replacement of fullerenes in PSCs. One choice is a polymer acceptor and the other is a small molecular acceptor. This chapter will have two main parts covering the material and morphological aspects of all-PSCs.
Article
We synthesize and systematically study a series of conjugated polymers with oligo(ethylene glycol) (OEG) or alkyl chain as the side chain and poly[2,7-fluorene-alt-5,5-(4,7-di-2-thienyl-2,1,3-benzothiadiazole)] as the polymer backbone. Replacing alkyl chain with OEG chain can decrease the π-π stacking distance of polymer backbone in thin film from 0.44 to 0.41 nm because OEG chain is more flexible than alkyl chain. As the result, the conjugated polymer with OEG side chain exhibits higher hole mobility, red-shifted absorption spectrum in thin film and smaller bandgap than those of the conjugated polymer with alkyl side chain. With the increase of the length of OEG side chain, the resulting conjugated polymers exhibit unchanged π-π stacking distance and decreased hole mobility. Moreover, owing to the large polarity of OEG chain, OEG side chain makes the conjugated polymer suitable for polymer solar cell (PSC) devices processed with polar nonhalogenated solvent, methoxybenzene. A power conversion efficiency of 4.04% is demonstrated with the resulting PSC devices. This work provides the new insight into the effect of OEG side chain on conjugated polymer, which can be used in the molecular design of novel conjugated polymer materials with excellent optoelectronic device performance. (Chemical Equation Presented).
Article
A series of new conjugated polymers based on the asymmetric benzo[1,2-b:4,5-b′]dithiophene (BDT) unit were designed and synthesized for use in bulk-heterojunction polymer solar cells. Each side chain of the BDT was tuned by introducing alkyl and alkoxy groups. The best solar cell efficiency was achieved in an asymmetric polymer device based on 4-octyl-8-octyloxy-BDT (7.64% PCE), which performed better than devices based on the symmetric dioctyl-BDT (6.48% PCE) or dioctyloxy-BDT (7.18% PCE). Further modification of the side chains, replacing octyloxy with butoxydiethoxy, improved the PCE to 8.12% due to the enhanced hole mobility, hole/electron mobility balance, and formation of tight contacts with the PEDOT:PSS layer. The effects of the side chains on the polymer HOMO energy levels and photovoltaic parameters were investigated.
Article
In recent years, conjugated polymers have attracted great attention in the application as photovoltaic donor materials in polymer solar cells (PSCs). Broad absorption, lower-energy bandgap, higher hole mobility, relatively lower HOMO energy levels, and higher solubility are important for the conjugated polymer donor materials to achieve high photovoltaic performance. Side-chain engineering plays a very important role in optimizing the physicochemical properties of the conjugated polymers. In this article, we review recent progress on the side-chain engineering of conjugated polymer donor materials, including the optimization of flexible side-chains for balancing solubility and intermolecular packing (aggregation), electron-withdrawing substituents for lowering HOMO energy levels, and two-dimension (2D)-conjugated polymers with conjugated side-chains for broadening absorption and enhancing hole mobility. After the molecular structural optimization by side-chain engineering, the 2D-conjugated polymers based on benzodithiophene units demonstrated the best photovoltaic performance, with power-conversion efficiency higher than 9%.
Article
In this paper, a new perylene diimide (PDI)-based acceptor Me-PDI4 with tetrahedral configuration (or 3D) has been synthesized and characterized. Solution-processed organic solar cells (OSCs) based on Me-PDI4 have been investigated and our results show that the device performance can reach as high as 2.73%. Our new design with tetrahedral configuration (or 3D) could be an efficient approach to push up the PCE of OSCs with non-fullerene acceptors.
Article
Harvesting solar energy from sunlight to generate electricity is considered as one of the most important technologies to address the future sustainability of humans. Polymer solar cells (PSCs) have attracted tremendous interest and attention over the past two decades due to their potential advantage to be fabricated onto large area and light-weight flexible substrates by solution processing at a lower cost. PSCs based on the concept of bulk heterojunction (BHJ) configuration where an active layer comprises a composite of a p-type (donor) and an n-type (acceptor) material represents the most useful strategy to maximize the internal donor-acceptor interfacial area allowing for efficient charge separation. Fullerene derivatives such as [6,6]-phenyl-C61 or 71-butyric acid methyl ester (PCBM) are the ideal n-type materials ubiquitously used for BHJ solar cells. The major effort to develop photoactive materials is numerously focused on the p-type conjugated polymers which are generally synthesized by polymerization of electron-rich donor and electron-deficient acceptor monomers. Compared to the development of electron-deficient comonomers (acceptor segments), the development of electron-rich donor materials is considerably flourishing. Forced planarization by covalently fastening adjacent aromatic and heteroaromatic subunits leads to the formation of ladder-type conjugated structures which are capable of elongating effective conjugation, reducing the optical bandgap, promoting intermolecular π-π interactions and enhancing intrinsic charge mobility. In this review, we will summarize the recent progress on the development of various well-defined new ladder-type conjugated materials. These materials serve as the superb donor monomers to prepare a range of donor-acceptor semi-ladder copolymers with sufficient solution-processability for solar cell applications.
Article
Current organic semiconductors for organic photovoltaics (OPV) have relative dielectric constants (relative permittivities, ε r) in the range of 2–4. As a consequence, Coulombically bound electron-hole pairs (excitons) are produced upon absorption of light, giving rise to limited power conversion efficiencies. We introduce a strategy to enhance ε r of well-known donors and acceptors without breaking conjugation, degrading charge carrier mobility or altering the transport gap. The ability of ethylene glycol (EG) repeating units to rapidly reorient their dipoles with the charge redistributions in the environment was proven via density functional theory (DFT) calculations. Fullerene derivatives functionalized with triethylene glycol side chains were studied for the enhancement of ε r together with poly(p-phenylene vinylene) and diketopyrrolopyrrole based polymers functionalized with similar side chains. The polymers showed a doubling of ε r with respect to their reference polymers in identical backbone. Fullerene derivatives presented enhancements up to 6 compared with phenyl-C61-butyric acid methyl ester (PCBM) as the reference. Importantly, the applied modifications did not affect the mobility of electrons and holes and provided excellent solubility in common organic solvents.
Article
Side chains in conjugated polymers have been primarily utilized as solubilizing groups. However, these side chains have roles that are far beyond. We advocate using side chain engineering to tune a polymer’s physical properties, including absorption, emission, energy level, molecular packing, and charge transport. To date, numerous flexible substituents suitable for constructing side chains have been reported. In this Perspective article, we advocate that the side chain engineering approach can advance better designs for next-generation conjugated polymers.
Article
Using an environmentally friendly solvent, N-methyl-2-pyrrolidone, PBDTTT-TEG, a polymer with benzodithiophene (BDT) and thieno[3,4-b]thiophene (TT) monomers and triethylene glycol monoether (TEG) side chains chains, can be processed into an active layer for a polymer solar cell (PSC). Combined with phenyl-C71 -butyric acid methyl ester (PC71 BM) as the acceptor, the resulting PSC has a power conversion efficiency (PCE) of 5.23%. This is the first example of an efficient polymer solar cells fabricated from non-aromatic and non-chlorinated solvent.
Article
In the past couple of years, remarkable progress has been made in solution-processable organic semiconducting materials for optoelectronics. The development of novel π-conjugated backbones has always been the central issue in this field. In contrast, flexible side chains are less developed and usually used only as solubilizing groups. In this Perspective, we highlight the effects of the flexible chains in organic semiconductors, including the influences of length, odd–even effect, substitution position, terminal groups, branching position, and chirality of alkyl chains, as well as some significant features of oligo(ethylene glycol) and fluoroalkyl chains. Although the roles of flexible chains in organic semiconducting materials are complex and differ when corresponding conjugated skeleton changes, in this Perspective, we emphasize the synergy of conjugated backbones and flexible side chains, which might significantly facilitate the understanding of the roles of flexible chains in structure–property relationship and promote the development of high-performance organic semiconductors.
Article
This paper reports the results of a systematic study of microwave dielectric relaxation times of poly(ethylene glycols), average molecular weight 200–9000, in dilute solutions of benzene at 9·83GHz. These results are compared with the values of relaxation times obtained earlier in carbon tetrachloride solutions. This shows that the average relaxation times τ0 and the relaxation time corresponding to segmental reorientation τ1 are influenced by the solvent environment. The variation in chain flexibility in these polymers with the increase in degree of polymerization and formation of intra- and inter-molecular hydrogen bonding in benzene and carbon tetrachloride solutions is discussed with the help of relaxation data. The relaxation time τ2 corresponding to group rotations has been determined. It is found that the τ2 value is independent of solvent environment and degree of polymerization, and may be attributed to the rotation of chain −OH end-groups around the C−O bonds in dynamic equilibrium, with the formation of a five-membered ring due to intra-molecular hydrogen bonding at the end of the chain. © 1998 SCI.
Article
The carrier collection efficiency (ηc) and energy conversion efficiency (ηe) of polymer photovoltaic cells were improved by blending of the semiconducting polymer with C60 or its functionalized derivatives. Composite films of poly(2-methoxy-5-(2′-ethyl-hexyloxy)-1,4-phenylene vinylene) (MEH-PPV) and fullerenes exhibit ηc of about 29 percent of electrons per photon and ηe of about 2.9 percent, efficiencies that are better by more than two orders of magnitude than those that have been achieved with devices made with pure MEH-PPV. The efficient charge separation results from photoinduced electron transfer from the MEH-PPV (as donor) to C60 (as acceptor); the high collection efficiency results from a bicontinuous network of internal donor-acceptor heterojunctions.
Article
Schmetterlinge im Bauch: Organische Feldeffekttransistoren mit einem freistehenden Film, selbstorganisiert aus einem amphiphilen schmetterlingförmigen Benzodithiophen, als aktiver Schicht (siehe Bild) wurden durch Übertragung aus Lösung erhalten. Die direkte Selbstorganisation des Films aus der Lösung bedeutet, dass für die Filmbildung kein Substrat benötigt wird.
Toward Solution-Processed High-Performance Polymer Solar Cells: from Material Design to Device Engineering
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Polymer Chemistry Series
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]fluorene Based D-A Copolymer with Strong Intermolecular Interactions toward Efficient Polymer Solar Cells
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Yang, M.; Lau, T.-K.; Xiao, S.; Gao, J.; Wang, W.; Lu, X.; Zhang, S.; Wu, J.; Zhan, C.; You, W. A Ladder-type Heteroheptacene 12H-Dithieno[2′,3′:4,5]thieno[3,2-b:2′,3′-h]fluorene Based D-A Copolymer with Strong Intermolecular Interactions toward Efficient Polymer Solar Cells. ACS Appl. Mater. Interfaces 2017, 9, 35159−35168.
Catalysed Stille Coupling Polymerization and the Resultant Photovoltaic Performance
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