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Asymmetrical side-chain engineering of small-molecule acceptors enable high-performance nonfullerene organic solar cells
摘要： Three new small molecules based on the benzo[1,2-b:4,5-b’]dithiophene (BDT) fused central core with different side-chains, namely DPBDT-4Cl, POBDT-4Cl and COBDT-4Cl, are designed and synthesized to investigate the side-chain effect on the properties of nonfullerene acceptors. DPBDT-4Cl has symmetrical phenylalkyl side-chains on the central BDT unit. In order to narrow the bandgap and reduce the steric hindrance, the phenylalkyl chains are systematically replaced with the flexible electron-donating alkoxy side-chain (POBDT-4Cl) and alkyl side-chain (COBDT-4Cl). As a result, POBDT-4Cl and COBDT-4Cl are characterized with asymmetry-featured side-chains. From DPBDT-4Cl to POBDT-4Cl to COBDT-4Cl, their light absorption abilities, molecular packing behaviors and crystallinity are gradually enhanced. The devices based on these three acceptors all show power conversion efficiencies (PCEs) over 11% with energy loss below 0.55 eV. Compared to DPBDT-4Cl, POBDT-4Cl and COBDT-4Cl obviously exhibit enhanced device performance with improved short-circuit current densities (Jsc) and fill factors (FFs), which mainly ascribe to their reduced charge recombination and enhanced charge transport. In addition, the COBDT-4Cl achieved a high efficiency of 13.5% with a Jsc of 21.8 mA cm-2 and an FF of 0.71. This result is among the best performance obtained from asymmetry-featured small molecules.
关键词： side-chains,benzo[1,2-b:4,5-b’]dithiophene,small-molecule acceptors,asymmetrical
更新于2025-09-19 17:13:59
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Novel swivel-cruciform 5,5′-bibenzothiadiazole based small molecule donors for efficient organic solar cells
摘要： 5,5′-bibenzothiadiazole (BBT), which is a dimer of widely used electron deficient building block benzothiadiazole (BT), offers great promise for developing highly efficient electron donors because of its unique structural features. However, a small quantity of work has been reported on BBT based donors, and their overall performances are still far behind those of their BT counterparts. In order to make a contribution in this regard, the novel small molecules were synthesized and applied as donor materials in the bulk heterojunction solar cells, in which the BBT was used as the central node. Compared with the corresponding linear BT based molecule, the swivel-cruciform BBT based molecule exhibited significantly enhanced photovoltaic performance with an impressive power conversion efficiency of 7.21%, which is the best reported device performance based on BBT-core materials in organic solar cells. These results indicate the great potential of BBT for high performance solar cells.
关键词： Swivel-cruciform structure,Organic solar cells,5,5′-bibenzothiadiazole unit,Small molecule donors
更新于2025-09-19 17:13:59
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Small-Molecule Donor/Polymer Acceptor Type Organic Solar Cells: Effect of Terminal Groups of Small-Molecule Donors
摘要： Small-molecule donor/polymer acceptor type (MD/PA-type) organic solar cells (OSCs) have the great advantage of superior thermal stability. However, very few small molecular donors can match polymer acceptors, leading to low power conversion ef?ciency (PCE) of MD/PA-type OSCs. In this work, we studied the effect of terminal groups of small molecular donors on the optoelectronic properties and OSC device performance of MD/PA-type OSCs. We select a benzodithiophene unit bearing carbazolyl substituents as the core, terthiophene as the bridging unit, and electron-withdrawing methyl 2-cyanoacetate, 3-ethylrhodanine, and 2H-indene-1,3-dione as the terminal groups to develop three small-molecule donors. With the increase of the electron-withdrawing capability of the terminal groups, the small molecular donors exhibit redshifted absorption spectra and downshifted LUMO levels. Among the three small-molecule donors, the one with 3-ethylrhodanine terminal group exhibits the best photovoltaic performance with the PCE of 8.0% in MD/PA-type OSCs. This work provides important guidelines for the design of small-molecule donors for MD/PA-type OSC applications.
关键词： organic solar cells,optoelectronic properties,Small-molecule donor
更新于2025-09-16 10:30:52
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Quantum Dots as Promising Theranostic Tools Against Amyloidosis: A Review
摘要： Amyloids are highly ordered beta sheet rich stable protein aggregates, which have been found to play a significant role in the onset of several degenerative diseases such as Alzheimer’s disease, Huntington’s disease, Parkinson’s disease, Type II diabetes mellitus and so on. Aggregation of proteins leading to amyloid fibril formation via intermediate(s), is thought to be a nucleated condensation polymerization process associated with many pathological conditions. There has been extensive research to identify inhibitors of these disease oriented aggregation processes. In recent times, quantum dots, with their unique physico-chemical properties have grabbed the attention of scientific community due to its applications in medical sciences. Quantum dots are nano-particles usually made of semiconductor materials which emit fluorescence upon radiation. The wavelength of fluorescence emission varies with changes in size of quantum dots. Several studies have reported significant inhibitory effects of these quantum dots towards amyloidogenesis, thereby presenting themselves as promising candidates against amyloidosis. Further, studies have also revealed amyloid detection capacity of quantum dots with sensitivity and specificity better than conventional probes. In the current review, we will discuss the various effects of quantum dots on protein aggregation pathways, their mechanism of actions and their potentials as effective therapeutics against amyloidosis.
关键词： quantum dots,Protein quality control,amyloid,degenerative disorders,small molecule inhibitors,aggregates
更新于2025-09-16 10:30:52
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Significantly improving the performance of polymer solar cells by the isomeric ending-group based small molecular acceptors: Insight into the isomerization
摘要： Compared to benzene-fused end-capping groups (EGs), thiophene-fused EGs have some unique characteristics due to the non-centrosymmetric structure of the thiophene ring, which make them easy to form different types of isomers. Here, we develop three isomeric brominated thiophene-fused EGs, which are linked to the IDTT core to acquire three novel isomeric small-molecule acceptors (SMAs) named ITC-2Br, ITC-2Br1, and ITC-2Br2. From ITC-2Br to ITC-2Br1, the change of the bromine substituent group on the thiophene ring has only a minor impact on the physicochemical properties and photovoltaic performance. However, from ITC-2Br to ITC-2Br2, the change in the fused sites on the thiophene leads to dramatically modified absorption, energy levels, and photovoltaic performance. Theoretical simulations provide an in-depth understanding of the absorption and electrochemical differences among the three acceptors. Thanks to the favorable properties, the ITC-2Br2-based polymer solar cells (PSCs) yield a significantly higher power conversion efficiency (PCE) (13.1%) than the devices based on ITC-2Br (10.9%) and ITC-2Br1 (11.9%). From the ITC-2Br-, ITC-2Br1- to the ITC-2Br2-based devices, the JSC and FF exhibit a monotonic increase similar to the trend of PCE, which demonstrates the success of the isomerization strategy, highlighting its future prospects for the development of high-performance SMAs.
关键词： polymer solar cells,power conversion efficiency,isomerization,small-molecule acceptors,end-capping groups
更新于2025-09-16 10:30:52
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A Trialkylsilylthienyl-Chain-Substituted Small-Molecule Acceptor with Higher-LUMO-Level and Reduced Bandgap for over 16%-Efficiency Fullerene-Free Ternary Solar Cells
摘要： The ternary approach using a smaller bandgap acceptor as the near infrared (NIR) absorber to increase the short-circuit current-density (Jsc) usually decreases the open-circuit voltage (Voc). In this contribution, we report a small-molecular acceptor, IN-4F, which has a reduced bandgap and a higher LUMO level than IT-4F, hence, enabling the concurrent increase in the Jsc and Voc when using as the acceptor guest of the host binary of PM6:IT-4F. IN-4F was judiciously designed by fusing benzodithiophene (BDT) and thieno[2′,3′:4,5]thieno to make a larger π?system so as to upshift the LUMO level and reduce the optical bandgap, and meanwhile, by substituting the BDT-4,8 positions with trialkylsilylthiophene chains to downshift the HOMO level to match the deep HOMO of PM6. Again, the structural similarity between IN-4F and IT-4F makes the nanoscaled homogeneous fine film-morphology and the ππ?stacking patterns both well-kept, hence, the fill-factor (FF) well-maintained. The IN-4F based binary solar cell shows 13.1% efficiency and its ternary solar cell blended with IT-4F supplies 14.9% efficiency. Again, the use of IN-4F as the guest acceptor of the PM6:Y6 system enables the increase of Voc due to its higher LUMO level, the increase of Jsc because of the increase of charge mobilities, and the maintenance of FF, affording 16.3% efficiency. This work demonstrates that the π?system extending plus the trialkylsilylthiophene chains substitution can be an effective strategy to synthesize a nonfullerene acceptor guest to realize a ternary material system which enables to increase Voc from its entanglement with Jsc (an issue of the current material approach).
关键词： small-molecule acceptor,higher LUMO level,nonfullerene acceptor,reduced bandgap,ternary solar cells
更新于2025-09-16 10:30:52
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Dipolar hole-blocking layers for inverted perovskite solar cells: effects of aggregation and electron transport levels
摘要： Herein, we report on the synthesis and investigation of two triazino-isoquinoline tetrafluoroborate electrolytes as hole-blocking layers in methylammonium triiodide perovskite photovoltaic devices with fullerene electron extraction layer. We find that increasing the thickness of the dipolar hole-blocking layer results in a gradual increase in the open-circuit voltage suggesting that aggregation of the molecules can enhance the dipole induced by the layer. This finding is confirmed by theoretical calculations demonstrating that while both molecules exhibit a similar dipole moment in their isolated state, this dipole is significantly enhanced when they aggregate. Ultra-violet photoemission spectroscopy measurements show that both derivatives exhibit a high ionization potential of 7 eV, in agreement with their effective hole-blocking nature demonstrated by the devices. However, each of the molecules shows a different electron affinity due to the increased conjugation of one of the derivatives. While the change in electron transport level between the two derivatives is as high as 0.3 eV, the difference in the open-circuit voltage of both types of devices is negligible, suggesting that the electron transport level plays only a minor role in determining the open-circuit voltage of the device. Numerical device simulations confirm that the increase in built-in potential, arising from the high dipole of the electrolyte layer, compensates for the non-ideal energetic alignment of the charge transport levels, resulting in high open-circuit voltages for a range of electron transport levels. Our study demonstrates that the application of small molecule electrolytes as hole-blocking layer in inverted architecture perovskite solar cells is a powerful tool to enhance the open-circuit voltage and provides useful guidelines for designing future generations of such compounds.
关键词： open-circuit voltage,small molecule electrolytes,aggregation,device simulation,perovskite solar cells
更新于2025-09-16 10:30:52
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Wide band-gap organic molecules containing benzodithiophene and difluoroquinoxaline derivatives for solar cell applications
摘要： Two new semiconducting organic small molecules, namely BDTQ-BDT(EH) and BDTQ-BDT(OC), were prepared by attaching electron accepting 2,3-didodecyl-6,7-difluoro-5,8-di(thiophen-2-yl)quinoxaline (DTQ) unit on 2,6-position of electron donating 4,8-bis(2-ethylhexyloxy)benzo[1,2-b:4,5-b’]dithiophene (BDT(EH)) and 4,8-bis(octyloxy)-benzo[1,2-b:4,5-b’]dithiophene (BDT(OC)) units. Molecule BDTQ-BDT(EH) showed higher thermal stability (5% weight loss temperature, Td “349 jC), slightly lower band-gap (Eg “2.10 eV) and deeper highest occupied molecular orbital energy level (HOMO “–5.36 eV) level compared to those (Td “336 jC, Eg “2.11 eV, and HOMO “–5.30 eV, respectively.) of the molecule BDTQ-BDT(OC). The organic solar cells (OSCs) made with the synthesized molecules as an electron donor and [6,6]-phenyl C71 butyric acid methyl ester (PC70BM) as an electron acceptor gave a maximum power conversion efficiency (PCE) of 1.20% and 0.83%, respectively, for BDTQ-BDT(EH) and BDTQ-BDT(OC). This study confirmed that the substituents attached on the 4,8-position of BDT unit greatly alter the properties of the resulting molecules.
关键词： small molecule solar cells,wide band-gap molecules,quinoxaline-based molecules,benzodithiophene-based molecules,organic solar cells
更新于2025-09-16 10:30:52
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Mediated Non-geminate Recombination in Ternary Organic Solar Cells Through a Liquid Crystal Guest Donor
摘要： The approach via ternary blends prompts the increase of absorbed photon density and resultant photocurrent enhancement in organic solar cells (OSCs). In contrast to actively reported high efficiency ternary OSCs, little is known about charge recombination properties and carrier loss mechanisms in these emerging devices. Here, through introducing a small molecule donor BTR as a guest component to the PCE-10:PC71BM binary system, we show that photocarrier losses via recombination are mitigated with respect the binary OSCs, owing to a reduced bimolecular recombination. The gain of the fill factor in ternary devices are reconciled by the change in equilibrium between charge exaction and recombination in the presence of BTR toward the former process. With these modifications, the power conversion efficiency in ternary solar cells receives a boost from 8.8 (PCE-10:PC71BM) to 10.88%. We further found that the voltage losses in the ternary cell are slightly suppressed, related to the rising charge transfer-state energy. These benefits brought by the third guest donor are important for attaining improvements on key photophysical processes governing the photovoltaic efficiencies in organic ternary solar cells.
关键词： charge transfer states,small molecule donor,voltage loss,ternary solar cells,charge recombination
更新于2025-09-16 10:30:52
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Achieving Efficient and Stable Morphology in Organic Solar Cells via Fine-tuning the Side-chains of Small Molecule Acceptors
摘要： Both the efficiency and stability of low cost organic solar cells are central components to meeting the requirements of commercialization for organic photovoltaics (OPV). Furthermore, the relationship between chemical structure of active material and morphology and its effects on efficiency and stability is still largely undetermined. Additionally, both the kinetic and thermodynamic morphology states of active layer can have a large impact on efficiency and stability, even when the chemical structures of materials applied in the active layer are especially same or similar. Here, using two series of acceptor-donor-acceptor (A-D-A) type small molecule acceptors (SMAs) with the similar backbone structure, we demonstrate the relevance of fine-tuned chemical structures with their solution and solid-state properties, further leading to significantly different behavior in terms of both device efficiency and stability. This is also partially due to the different morphology states caused by such fine chemical structure tuning. Our results indicate that a delicate balance of molecular aggregation and ordered stacking morphology is not only required to achieve but also could lead to both high efficiency and stability. Thus, among the two series of molecules, UF-EH-2F with both optimal length and steric hindrance of side-chains achieves the preponderant morphology in its corresponding device, where its morphology “Efficient State” and “Stable State” are almost overlapped and thus lead to both the highest efficiency (PCE = 13.56%) and best stability. Our results indicate that it is highly possible to achieve the morphology state required for both high efficiency and stability simultaneously by fine-tuning the chemical structure of active materials for organic solar cells.
关键词： small molecule acceptors,efficiency,side-chains,morphology,organic solar cells,stability
更新于2025-09-16 10:30:52