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Effect of the length of a symmetric branched side chain on charge transport in thienoisoindigo-based polymer field-effect transistors
摘要： Compounds consisting of the electron-accepting thienoisoindigo (TIIG) moiety with branched alkyl side chains of various lengths were each copolymerized with thiophenylene vinylene thiophene (TVT) and selenophenylene vinylene selenophene (SVS) donor moieties, to investigate how the length of the side chain between the branch point and backbone affects the microstructure and charge transport of thin films made of these TIIGTVT and TIIGSVS copolymers. All of the organic field-effect devices based on these copolymers exhibited p-type behaviors, and these devices displayed hole mobility values as high as 1.15 cm2/V/s. Interestingly, the longer side chains in both series of TIIGTVT and TIIGSVS copolymers, the more improved was the molecular ordering of the thin films. But the relationship between charge mobility and side chain length differed for these two series of copolymers, a result attributed to differences between the microstructures of their films. The TIIGTVT series showed localized aggregation, with the greater length of the side chain between the branch point and backbone enhancing the charge transport by increasing the quantity and average size of the aggregates. In contrast, the TIIGSVS series showed long-range order, and aggregates that were too large and prevented charge transport.
关键词： side-chain engineering,thienoisoindigo,polymer field-effect transistor,Polymeric semiconductors
更新于2025-09-23 15:21:21
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Highly Efficient All-Small-Molecule Organic Solar Cells with Appropriate Active Layer Morphology by Side Chain Engineering of Donor Molecules and Thermal Annealing
摘要： It is very important to fine-tune the nanoscale morphology of donor:acceptor blend active layers for improving the photovoltaic performance of all-small-molecule organic solar cells (SM-OSCs). In this work, two new small molecule donor materials are synthesized with different substituents on their thiophene conjugated side chains, including SM1-S with alkylthio and SM1-F with fluorine and alkyl substituents, and the previously reported donor molecule SM1 with an alkyl substituent, for investigating the effect of different conjugated side chains on the molecular aggregation and the photophysical, and photovoltaic properties of the donor molecules. As a result, an SM1-F-based SM-OSC with Y6 as the acceptor, and with thermal annealing (TA) at 120 °C for 10 min, demonstrates the highest power conversion efficiency value of 14.07%, which is one of the best values for SM-OSCs reported so far. Besides, these results also reveal that different side chains of the small molecules can distinctly influence the crystallinity characteristics and aggregation features, and TA treatment can effectively fine-tune the phase separation to form suitable donor–acceptor interpenetrating networks, which is beneficial for exciton dissociation and charge transportation, leading to highly efficient photovoltaic performance.
关键词： small molecule donor materials,all-small-molecule organic solar cells,interpenetrating networks,side-chain engineering,thermal annealing
更新于2025-09-23 15:21:01
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Bandgap Tailored Nonfullerene Acceptors for Low-Energy-Loss Near-Infrared Organic Photovoltaics
摘要： A series of A?π?D?π–A type nonfullerene acceptors (NFAs) was designed and synthesized with the goal of optimizing light absorption and energy losses in near-infrared (NIR) organic solar cells (OSCs) principally through the use of side chain engineering. Specific molecules include p-IO1, o-IO1, p-IO2, and o-IO2 with optical bandgaps of 1.34 eV, 1.28 eV, 1.24 eV, and 1.20 eV, respectively. Manipulating the optoelectronic properties and intermolecular organization by substituting bulky phenylhexyl (p-) for linear octyl chains (o-) and replacing bisalkoxy (-O2) with alkyl-alkoxy combination (-O1) allows one to target energy bandgaps and achieve a favorable bulk heterojunction morphology when in the presence of the donor polymer PTB7-Th. Solar cells based on o-IO1 and PTB7-Th exhibit an optimal power conversion efficiency of 13.1%. The excellent photovoltaic performance obtained with the o-IO1 acceptor can be attributed to a short-circuit current of 26.3 mA cm?2 and energy losses on the order of 0.54 eV. These results further highlight how side chain engineering is a straightforward strategy to tune the molecular design of n-type molecular semiconductors, particularly in the context of near-infrared high efficiency organic photovoltaics.
关键词： side chain engineering,nonfullerene acceptors,power conversion efficiency,organic solar cells,near-infrared
更新于2025-09-19 17:13:59
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Twoa??Dimension Conjugated Acceptors Based on Benzodi(cyclopentadithiophene) Core with Thiophenea??Fused Ending Group for Efficient Polymer Solar Cells
摘要： The previously reported nonfullerene small molecule ITIC-SF achieved via side chain tuning, promotes the power conversion efficiency of polymer solar cells (PSCs) with PBDB-T-SF as the donor from 10.1% and ITIC2 acceptors up to 12.2% for ITIC-SF acceptors. To further this research, benzene end groups of molecules are herein substituted with thiophene rings, obtaining two new molecules BDTCH-IC with alkylthio substituents, and BDTSF-IC with alkylthio and fluorine substituents on their thiophene-conjugated side chains. The absorption edges of BDTCH-IC and BDTSF-IC are red-shifted to 824 and 793 nm, respectively. Strengthened molecular crystallinity, promoted charge extraction, and upgraded morphology endorse the advancement of photovoltaic performance of the small molecular acceptors. Using donor PM6, the two small molecule acceptors show good photovoltaic performance, although the highest occupied molecular orbit energy offsets are small between donor and acceptor materials. As a combination of side-chain and end-group engineering, the photovoltaic performance of the PSCs is increased to 13.1%, together with the best short-circuit current (JSC) and fill factor reported thus far for this series of molecules. The results indicate that the modification of side chain and end groups is an effective way to improve the photovoltaic performance of small molecule acceptors.
关键词： small molecules acceptors,nonfullerenes,end groups,side-chain engineering,polymer solar cells
更新于2025-09-19 17:13:59
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Effects of Short‐Axis Alkoxy Substituents on Molecular Self‐Assembly and Photovoltaic Performance of Indacenodithiophene‐Based Acceptors
摘要： The effects of central alkoxy side chain length of a series of narrow bandgap small molecule acceptors (SMAs) on their physicochemical properties and on the photovoltaic performance of the SMA-based polymer solar cells (PSCs) are systematically investigated. It is found that the ordered aggregation of these SMAs in films is enhanced gradually with the increase of alkoxy chain length. The single-crystal structures of these SMAs further reveal that small changes in the side chain length can have a dramatic impact on molecular self-assembly. The short-circuit current density and power conversion efficiency values of the corresponding PSCs increase with the increase of the side chain length of the SMAs. The π–π coherence length of the SMAs in the active layers is increased with the increase of the side chain length, which could be the reason for the increase of the Jsc in the PSCs. The results indicate that small changes in side chain length can have a dramatic impact on the molecular self-assembly, morphology, and photovoltaic performance of the PSCs. The structure–performance relationship established in this study can provide important instructions for the side chain engineering and for the design of efficient SMAs materials.
关键词： polymer solar cells,side chain engineering,morphology,small molecule acceptors,molecular self-assembly
更新于2025-09-19 17:13:59
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A distorted lactam unit with intramolecular hydrogen bonds as the electron donor of polymer solar cells
摘要： A novel distorted lactam motif, namely 4,40-dialkyl-[6,60-bithieno[3,2-b]pyridine]-5,50(4H,40H)-dione (BTP), could lock itself by intramolecular hydrogen bonds. In view of the potential of the motif, two D–A conjugated polymers, PBDT-BTP-HD and PBDT-BTP-OD, with two different long side chains consisting of 4,8-bis(5-(2-ethylhexyl)thiophen-2-yl)benzo[1,2-b:4,5-b0]dithiophene (BDT) as a donor unit and BTP as an acceptor unit were designed and synthesized. Furthermore, the photophysical, electrochemical and photovoltaic properties of both polymers were investigated. The morphologies and molecular ordering of the neat polymers and blend films were also probed to relate the side chain structures with aggregation states and device parameters. The device based on PBDT-BTP-OD with IT-M exhibited a power conversion efficiency of up to 9.54% thanks to the synergistic effect of the building blocks and side-chain engineering. As a result, it is successfully demonstrated that the novel distorted lactam BTP is a promising building block in organic solar cells.
关键词： side-chain engineering,intramolecular hydrogen bonds,electron donor,distorted lactam,polymer solar cells
更新于2025-09-11 14:15:04
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Self-doping small molecular conjugated electrolytes enabled by n-type side chains for highly efficient non-fullerene polymer solar cells
摘要： We developed a series of novel small molecular conjugated electrolytes (SMCEs) via side chain engineering. The introduced n-type 1,3,4-thiadiazole/1,3,4-oxadiazole side chains featured the related SMCEs with self-doping nature and high electron conductive property. On using as cathode interlayers in non-fullerene-polymer solar cells, a high power conversion efficiency (PCE) of up to 13.21% was achieved with an excellent thickness-insensitive property.
关键词： thickness-insensitive property,side chain engineering,power conversion efficiency,non-fullerene polymer solar cells,small molecular conjugated electrolytes
更新于2025-09-11 14:15:04
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Side-Chain Engineering of Donor–Acceptor Conjugated Small Molecules As Dopant-Free Hole-Transport Materials for Efficient Normal Planar Perovskite Solar Cells
摘要： Simultaneously improving efficiency and stability, which are particularly crucial factors for the commercialization of perovskite solar cells (PSCs), remains a major challenge. For high efficiency normal PSCs, the development of stable dopant-free hole-transport materials (HTMs) seems imperative. Here, we developed potential donor-acceptor (D-A) small molecules (BTTI) as HTMs for normal planar PSCs. Through tailoring its alkyl side chain length as BTTI-C6, BTTI-C8 and BTTI-C12, our results show that upon shortening the side chain of BTTI, the hole mobility, film-forming capability and resultant device performance were remarkably improved, with device conversion efficiencies of 19.69% for BTTI-C6, 18.89% for BTTI-C8 and 17.49% for BTTI-C12. Meanwhile, compared to those made with the routine doped Spiro-OMeTAD, devices based on our dopant-free HTMs exhibited significantly improved stability. This work paves the way to the development of effective dopant-free HTMs for high performance PSCs.
关键词： Perovskite solar cells,Donor-acceptor conjugated small molecules,Dopant-free,Hole-transport materials,Side chain engineering
更新于2025-09-11 14:15:04