6 Search Results

Herein, interfacial engineering is shown to improve the thermal stability of non-fullerene bulk-heterojunction (BHJ) OPVs to a practical level. An amphiphilic dendritic block copolymer (DBC) is developed through a facile coupling method and employed as the surface modifier of ZnO electron-transporting layer in inverted OPVs. Besides showing distinct self-assembly behavior, the synthesized DBC possesses high compatibility with plasmonic gold nanoparticles (NPs) due to the constituent malonamide and ethylene oxide units. The hybrid DBC@AuNPs interlayer is shown to improve device's performance from 14.0% to 15.4% because it enables better energy-level alignment and improves interfacial compatibility at the ZnO/BHJ interface. Moreover, themore » DBC@AuNPs interlayer not only improves the interfacial thermal stability at the ZnO/BHJ interface but also endows a more ideal BHJ morphology with an enhanced thermal robustness. The derived device reserves 77% of initial PCE after thermal aging at 65 degrees C for 3000 h and yields an extended T₈₀ lifetime of >1100 h when stored at a constant thermal condition at 65 degrees C, outperforming the control device. Finally, the device is evaluated to possess aT(80)lifetime of over 1.79 years at room temperature (298 K) when stored in an inert condition, showing great potential for commercialization.« less

The backbone of diketopyrrolopyrrole-thiophene-vinylene-thiophene-based polymer semiconductors (PSCs) is modified with pyridine (Py) or bipyridine ligands to complex Fe(II) metal centers, allowing the metal–ligand complexes to act as mechanophores and dynamically crosslink the polymer chains. Here, mono- and bi-dentate ligands are observed to exhibit different degrees of bond strengths, which subsequently affect the mechanical properties of these Wolf-type-II metallopolymers. The counter ion also plays a crucial role, as it is observed that Py-Fe mechanophores with non-coordinating BPh₄– counter ions (Py-FeB) exhibit better thin film ductility with lower elastic modulus, as compared to the coordinating chloro ligands (Py-FeC). Interestingly, besides mechanical robustness,more » the electrical charge carrier mobility can also be enhanced concurrently when incorporating Py-FeB mechanophores in PSCs. This is a unique observation among stretchable PSCs, especially that most reports to date describe a decreased mobility when the stretchability is improved. Next, it is determined that improvements to both mobility and stretchability are correlated to the solid-state molecular ordering and dynamics of coordination bonds under strain, as elucidated via techniques of grazing-incidence X-ray diffraction and X-ray absorption spectroscopy techniques, respectively. This study provides a viable approach to enhance both the mechanical and the electronic performance of polymer-based soft devices.« less

Polymer semiconductors (PSCs) are a desirable class of materials for next-generation electronics. However, the conformational complexity associated with macromolecules, as well as the presence of unique inter- and intrachain interactions, make it challenging to control the morphology of PSCs. Previously, it has been reported that beyond a certain molecular weight, thin-film charge carrier mobility typically drops due to reduced crystallinity and increased entanglement. In this work, the use of an insulating secondary matrix polymer, polystyrene-block-poly(ethylene-ran-butylene)-block-polystyrene (SEBS), is shown to induce molecular ordering of PSCs across multiple length scales. Aggregation-induced molecular ordering in SEBS/PSC hybrid films is strongly correlated to themore » molecular weight of the semiconducting component. The higher the molecular weight of PSC used to blend with SEBS, the greater the observed improvement in polymer aggregation and orientation. This leads to a 5-fold increase of charge carrier mobility, from 0.3 to 1.5 cm2 V^–1 s^–1 (P-97k), in field-effect transistors (FETs) with only 30 wt % of the semiconducting polymer in SEBS. Moreover, mobility can be further elevated to 2 cm2 V^–1 s^–1 using an extensional flow-driven solution shearing deposition method. The findings here on using a secondary polymer matrix to dramatically improve the molecular organization and charge transport of a high-molecular-weight PSC are a useful morphological control strategy. It can also be carried out using nonhalogenated solvents, such as $$p$$-xylene, which are more environmentally benign and industrially relevant than commonly used chlorinated solvents.« less

Abstract A high performance diketopyrrolopyrrole (DPP)–based semiconducting polymer is modified with ligands to enable metal coordination, and its subsequent effect as field‐effect transistors is investigated. In specific, pyridine‐2,6‐dicarboxamide (PDCA) units are incorporated in a DPP–based polymer backbone with a content from 0 to 30 mol%, and the resulting polymers are then mixed with Fe(II) ions. The coordination and spontaneous oxidation converts Fe(II) to Fe(III) ions to result in Fe(III)‐containing metallopolymers. The resulting metallopolymers are observed to show good solubility in organic solvents and can be easily processed as thin films. The charge transport characteristics are subsequently investigated through the fabricationmore » of field–effect transistor devices, in which an enhanced charge carrier mobility with the Fe(III)‐containing metallopolymers is observed. In specific, an almost twofold improvement in the charge carrier mobility is obtained for the 20% PDCA‐containing polymer after Fe coordination (from 0.96 to 1.84 cm ² V ⁻¹ s ⁻¹ ). Furthermore, the operation stability of the metallopolymer‐based devices is found to be significantly improved with low bias stress. Its superior electrical characteristics are attributed to the doping effect of the Fe ions. This study indicates that incorporation of appropriate metallic ions to polymer presents a viable approach to enhance the performance of polymer–based transistor devices.« less

The design of polymer semiconductors possessing high charge transport performance, coupled with good ductility, remains a challenge. Understanding the distribution and behavior of both crystalline domains and amorphous regions in conjugated polymer films, upon an applied stress, shall provide general guiding principles to design stretchable organic semiconductors. Structure–property relationships (especially in both side chain and backbone engineering) are investigated for a series of poly(tetrathienoacene-diketopyrrolopyrrole) polymers. It is observed that the fused thiophene diketopyrrolopyrrole-based polymer, when incorporated with branched side chains and an additional thiophene spacer in the backbone, exhibits improved mechanical endurance and, in addition, does not show crack propagationmore » until 40% strain. Furthermore, this polymer exhibits a hole mobility of 0.1 cm2 V^-1 s^-1 even at 100% strain or after recovered from strain, which reveals prominent continuity and viscoelasticity of the polymer thin film. In conclusion, it is also observed that the molecular packing orientations (either edge-on or face-on) significantly affect the mechanical compliance of the polymer films. The improved stretchability of the polymers is attributed to both the presence of soft amorphous regions and the intrinsic packing arrangement of its crystalline domains.« less