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The spacer length effect of seven poly(DPP-alt-terthiophene)s with tributylsilylalkyl side chains was systematically studied, and the polymer SiC6 exhibited the best device performance with a reliable hole mobility up to 2.69 cm2 V−1 s−1 from o-xylene.

Two conjugated polymers (CPs) Fu-F and Fu-Cl that are soluble in a green solvent anisole were successfully synthesized via direct arylation polycondensation (DArP) using a furan-flanked diketopyrrolopyrrole (DPP) derivative (FDPP-Br) as the C–Br monomer and (E)-1,2-bis(3,4-difluorothien-2-yl)ethene (4FTVT) or (E)-1,2-bis(3,4-dichlorothien-2-yl)ethene (4ClTVT) as the C–H monomer. With anisole as the processing solvent and polyethylenimine ethoxylated (PEIE) as the electrode modification layer, n-type organic thin-film transistors (OTFTs) of the polymers were fabricated via bar-coating. The electron mobility (μe) of the devices based on Fu-Cl was only in the magnitude of 10−2 cm2 V−1 s−1, owing to the unfavoured fine granular film morphology. In contrast, Fu-F films showed fibre-like morphology with the polymer chains aligned along the bar-coating direction, which is favourable for the charge transport in OTFTs. Therefore, Fu-F delivered much better device performance with the μe of up to 2.79 cm2 V−1 s−1. Our study demonstrates that green solvent processed high mobility CPs can be synthesized by DArP, an emerging eco-friendly protocol for the synthesis of CPs.

n-Type conjugated polymers were synthesized by environmentally benign direct arylation polycondensation. With these polymers, OTFTs with μe of up to 0.72 cm2 V−1 s−1 were fabricated.

Two o-carborane-based π-conjugated macrocycles are synthesized via oxidative coupling of acetylene-terminated o-carborane precursors. The single-crystal X-ray diffraction analysis unambiguously revealed their unique porous supramolecular structures, which display micropore characteristics. The...

How to achieve high crystallinity and suitable phase scale simultaneously from the perspective of molecular engineering remains a long-standing challenge for all-small-molecule organic solar cells (ASM-OSCs). Herein, two small molecule...

Quinoidal compounds have great potential utility as high-performance organic semiconducting materials because of their rigid planar structures and extended π-conjugation. However, the existence of E and Z isomers adversely affects the charge-transport properties of quinoidal compounds. In this study, we developed three isomerically pure oxindole-terminated quinoids by introducing chlorine atoms in the quinoidal core. The synthesized quinoids were confirmed to have a Z,Z configuration by means of 1H NMR spectroscopy, density functional theory calculations, and single-crystal X-ray analysis. Importantly, the strategy of chlorination allowed to maintain low-lying frontier molecular orbital energy levels and ensure favorable intermolecular packing. Consequently, all three quinoidal compounds showed n-type transport characteristics in organic thin-film transistors, with electron mobilities up to 0.35 cm2 V-1 s-1, which is the highest value reported to date for oxindole-terminated quinoids. We believe that our study can provide new guidelines for the design of isomerically pure quinoids with high electron mobilities.

Polymer semiconductors with large elastic recovery (ER) under high strain in thin film state are highly desirable for stretchable electronics. Here we report a type of stretchable semiconductor PU(DPP)

Direct arylation of 2,7-dibromofluorene with n-octyl, 6-diethoxylphosphorylhexyl, 6-(N,N-diethylamino)hexyl or 6-bromohexyl side chains and 1,2,4,5-tetrafluorobenzene (TFB) were conducted to invest...

Polythiophenes, with merits of low cost and high scalability of synthesis, have received growing interest in organic solar cells. To date, the best-performing polythiophene:nonfullerene solar cells exhibit typical power conversion efficiencies (PCEs) of 10%–12%, which is much lower than those employing PM6- and D18-type polymers. This inferior performance is mostly limited by the improper miscibility between polythiophene and acceptors. Efforts on engineering the molecular structure to systematically tune the miscibility are required. With the aid of group contribution calculations, the miscibility of polythiophene:nonfullerene blend system was finely tuned by varying the ratios of siloxane-terminated chains and alkyl chains in ester-substituted polythiophenes through random copolymerization. Based on a series of the polythiophene and nonfullerene acceptors, the detailed analysis of blend miscibility and performance reveals a surprising anticorrelation between the Flory-Huggins interaction parameter ( χ aa) and the optimal time of solvent vapor annealing for device performance across these systems. Primarily due to the slightly higher χ aa, the blend of PDCBT-Cl-Si5 and ITIC-Th1 results in a record-high PCE of 12.85% in polythiophene:nonfullerene solar cells. The results not only provide a calculation-guided approach for molecular design but also prove that precise control of the miscibility is an effective way to design high-performance polythiophene:nonfullerene blends and beyond.

Due to the simple structure and excellent scalability, regioregular poly(3-hexylthiophene) (P3HT) has become much more popular as a low-cost donor polymer partner with the emerging nonfullerene acceptors in recent years. Presently, the application and the molar mass dependence of direct arylation polycondensation (DArP) prepared P3HT in fullerene-free organic solar cells have not been explored yet. In this work, five batches of P3HT with weight-average molar mass ranging from 8.9 kg mol−1 to 89.1 kg mol−1 were successfully prepared via DArP, with the aim to detail the interaction–performance relationships in the state-of-the-art P3HT:nonfullerene photovoltaic blend, namely P3HT:ZY-4Cl. Our thermodynamic analysis revealed that the amorphous–amorphous interaction parameters strongly depend on the P3HT molar mass and can be varied by a factor of 2.75. Owing to the best π–π stacking order deduced from grazing incidence X-ray diffraction and the smallest domain size, the blend based on the medium molar mass batch (25.5 kg mol−1) delivered the highest current density, fill factor, and power conversion efficiency up to ∼10% among the five systems. Our study confirmed that DArP is an effective protocol for the synthesis of P3HT for efficient non-fullerene polymer solar cells and the established relationships can be applied to screen the best batch for P3HT-based organic photovoltaics.

Bulk-heterojunction active layers prepared by a blend casting (BC) method have been predominantly used for more than two decades in the construction of organic/polymer solar cells (OSCs) with high efficiencies and stability. Sequential deposition (SD) with donor and acceptor layers coated sequentially is a facile but effective strategy to fabricate efficient OSCs and holds great promise to address the drawbacks of bulk-heterojunctions. Compared with OSCs prepared by the BC method, SD processed OSCs can separately engineer different layers, realizing an ideal profile of vertical component distribution, which is favorable for charge generation, transport and collection. SD processed OSCs based on nonfullerene acceptors have progressed rapidly, with a striking power conversion efficiency (PCE) up to >18% achieved recently. In this review, we summarize recent advances in the optimization of SD processed OSCs with particular emphasis on the role of processing solvents and co-solvents, solvent additives and the third components. Moreover, we comprehensively discuss the impact of the SD method on device stability and provide an overview of the potential of the SD method in constructing large-area solar cell panels. Finally, we outline the existing challenges and prospects of the SD method in industrial production. We hope that this review can provide some inspiration for the performance improvement of SD processed OSCs and advance their commercial applications.

High-mobility conjugated polymers (CPs) that can be synthesized in a large scale by direct arylation polycondensation (DArP) are highly desired for printable electronics. To realize this purpose, a...

Summary Polythiophene (PT) and its derivatives have attracted long-standing attention in the organic photovoltaic community for their low cost and high scalability of synthesis. However, due to the lack of rational guidelines in controlling morphology and matching materials, the power conversion efficiencies (PCEs) based on PTs reported so far are generally below 10%. Here, we establish the first-ever relationship between miscibility, morphology, and device performance of binary blends, based on various nonfullerene acceptors (ITIC-Th1, ITIC, IT4F, IDIC, and Y6) and a PT derivative named PDCBT-Cl by scattering and calorimetric characterizations. Benefiting from a properly quenched mixed phase, PDCBT-Cl:ITIC-Th1 system shows the best efficiency of over 12%. Conversely, the blend of PDCBT-Cl and the star acceptor Y6 remained in a homogeneous state due to their high miscibility, resulting in abysmal performance with PCE of 0.5%. Specific guidelines are also proposed to remediate the performance of PDCBT-Cl:Y6, which are crucial for advancing their practical applications.

Understanding the key factors influencing the mechanical and electrical properties of semiconducting polymers is crucial to the development of stretchable electronics. In this work, a high-mobility...

Polymer solar cells (PSCs) based on polymer donors and nonfullerene small molecule acceptors are a very attractive technology for solar energy conversion, and their performance is heavily determined by film morphology. It is of considerable interest to reveal instructive morphology-performance relationships of these blends. This feature article discusses the recent advances in analysing the morphology formation of nonfullerene PSCs with an effective polymer thermodynamic quantity, i.e., Flory-Huggins interaction parameter χ. In particular, guidelines of high and low χ systems are summarized. The fundamental understanding of χ and its correlations to film morphology and photovoltaic device parameters is of utmost relevance for providing essential material design criteria, establishing suitable morphology processing guidelines, and thus advancing the practical applications of PSCs based on nonfullerene acceptors.

The electronic properties of quinoidal compounds can be modulated both by their central quinoidal cores and by their end groups. However, there have only been a few studies of the effects of end-groups on the electronic properties of quinoidal compounds, due to synthetic challenges. In this study, we have prepared four quinoidal compounds, IDOTT, 2FIDOTT, 4FIDOTT, and 6FIDOTT, with different numbers of fluorine (F) atoms on the terminal isatin units, and the effects of terminal fluorination on their optical properties, energy levels, molecular packing (as single crystals and thin-films), and electron transport properties have been evaluated. The incorporation of F atoms decreased the HOMO/LUMO levels and blue-shifted the absorption spectra. All four quinoidal compounds showed n-type transport behavior in organic thin-film transistor (OTFT) devices, but their electron mobilities strongly depended on the number of F atoms. Among these compounds, 4FIDOTT exhibited the highest electron mobility (0.16 cm2 V−1 s−1), due to its two-dimensional electron transport, highly ordered thin-film, and appropriate morphology.

A series of 1,3-indandione-terminated π-conjugated quinoids were synthesized by alkoxide-mediated rearrangement reaction of the respective alkene precursors, followed by air oxidation. This new protocol allows access to quinoidal compounds with variable termini and cores. The resulting quinoids all show LUMO levels below -4.0 eV and molar extinction coefficients above 105 L mol-1 cm-1 . The optoelectronic properties of these compounds can be regulated by tuning the central cores as well as the aryl termini ascribed to the delocalized frontier molecular orbitals over the entire molecular skeleton involving aryl termini. n-Channel organic thin-film transistors with electron mobility of up to 0.38 cm2 V-1 s-1 were fabricated, showing the potential of this new class of quinoids as organic semiconductors.

Three narrow band gap (NBG) acceptors, namely

Organic electrode materials have emerged as promising alternatives to conventional inorganic materials because of their structural diversity and environmental friendliness feature. However, their low energy densities, limited by the single-electron reaction per active group, have plagued the practical applications. Here, we report a nitroaromatic cathode that performs a six-electron reaction per nitro group, drastically improving the specific capacity and energy density compared with the organic electrodes based on single-electron reactions. Based on such a reaction mechanism, the organic cathode of 1,5-dinitronaphthalene demonstrates an ultrahigh specific capacity of 1,338 mAh⋅g

Aggregation structure formation of conjugated polymers is a fundamental problem in the field of organic electronics and remains poorly understood. Herein, we thoroughly show the molar mass dependence of the aggregation structure of a high-mobility conjugated copolymer (TDPP-Se) comprising thiophene-flanked diketopyrrolopyrrole and selenophene. Five batches of TDPP-Se are prepared with number-average molecular weights (Mn ) varied greatly from 21 to 135 kg mol-1 . We combine small-angle neutron scattering and transmission electron microscopy to probe the solution structure of these polymers, consistently using a deuterated solvent. All the polymers adopt the one-dimensional (1D) rod-like aggregation structures and the radius of 1D rod is not sensitive to the Mn while the length increases monotonically with the Mn . By utilizing the ordered packing of the aggregated structure in solution, we prepare highly aligned and ordered film and thereafter realize a reliable hole mobility of up to 13.8 cm2 V-1 s-1 in organic thin-film transistors with the moderate Mn batch via bar coating. The hole mobility is among the highest values reported for diketopyrrolopyrrole-based polymers in the literature. This work paves the way to visualize the real aggregated structure of polymer semiconductors in solution state and sheds light on the aggregation structure control of high-performance electronic devices. This article is protected by copyright. All rights reserved.

The stretchability and stretch-induced structural evolution of organic solar cells (OSCs) are pivotal for their collapsible, portable, and wearable applications, and they are mainly affected by the complex morphology of active layers. Herein, a highly ductile conjugated polymer P(NDI2OD-T2) was incorporated into the active layers of high-efficiency OSCs based on nonfullerene small molecule acceptors to simultaneously investigate the morphological, mechanical, and photovoltaic properties and structural evolution under stretching of ternary blend films with various acceptor contents. The structural robustness of the blend films was indicated by their stretch-induced structural evolution, which was monitored in real-time by a combination of in-situ wide/small angle X-ray scattering. We found that adding the soft P(NDI2OD-T2) can enhance the stretchability and structural robustness of ternary blend films by increasing entangled chains and tie chains to dissipate strain. Furthermore, the stretchability of the ternary blends can be superbly predicted by the three-dimensional equivalent box model. This work provides instructive insight and guidance for designing stretchable electronics and predicting the stretchability of multi-component blends. This article is protected by copyright. All rights reserved.