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High-efficiency non-halogenated solvent processable polymer/PCBM solar cells <i>via</i> fluorination-enabled optimized nanoscale morphology
摘要： PNTz4T-based polymers have been extensively employed in high-efficiency fullerene-based polymer solar cells (PSCs) with a power conversion efficiency (PCE) of approximately 10.0% due to the high crystallinity of these polymers. The introduction of two fluorine atoms into PNTz4T to synthesize the PNTz4T-2F polymer has boosted the PCE to 10.6%, but the introduction of four fluorine atoms to synthesize the PNTz4T-4F polymer negatively affects the efficiency (PCE ? 6.5%), implying that the number of fluorine atoms is not yet optimized. We have developed a new synthetic route for a novel monofluoro-bithiophene monomer and successfully synthesized a novel PNTz4T-1F polymer. The fullerene-based PSCs based on our novel PNTz4T-1F polymer processed using a halogen-free solvent system demonstrated an outstanding PCE of 11.77% (11.67% certified), representing the highest PCE reported thus far in the literature. Due to the optimum molecular ordering/packing, improved interaction with PC71BM and interconnectivity between photoactive material domains, PNTz4T-1F-based PSCs exhibit lower charge carrier recombination and enhanced charge carrier mobility levels, leading to a substantially high photocurrent density (20.37 mA cm(cid:2)2). These results create new means to tune the structural properties of polymers, ultimately leading to the realization of this class of solar cells for practical applications.
关键词： polymer solar cells,nanoscale morphology,halogen-free solvent,power conversion efficiency,fluorination
更新于2025-09-16 10:30:52
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Introducing an identical benzodithiophene donor unit for polymer donors and small-molecule acceptors to unveil the relationship between the molecular structure and photovoltaic performance of non-fullerene organic solar cells
摘要： The side-chain conjugation strategy is adopted in the synthesis of heptacyclic non-fullerene electron acceptors, ITIC2, ITIC-S, and ITIC-SF, for application in organic solar cells (OSCs). The new ITIC-SF molecule features a BDT-SF building block which is the electron-donating component in the widely used donor PBDB-T-SF. Compared with ITIC-S without fluorine substituents, fluorination weakens the crystallinity of ITIC-SF, while the intermolecular interaction between the PBDB-T-SF donor and ITIC-SF acceptor, containing the same BDT-SF building block, results in the increased crystallinity of the corresponding blend films. The OSC based on PBDB-T-SF:ITIC-SF exhibits a champion power conversion efficiency (PCE) of 12.1%, higher than the PCE of 10.1% for the device based on PBDB-T-SF:ITIC2 and the PCE of 11.6% for the device based on PBDB-T-SF:ITIC-S. The better photovoltaic performance of the OSC based on PBDB-T-SF:ITIC-SF is benefitted from the weaker bimolecular recombination and more efficient charge transfer and extraction of the device. The structure–property relationship of the non-fullerene acceptors revealed in this work will play an important role in instructing the molecular structure design of high performance photovoltaic materials for the development of OSCs.
关键词： organic solar cells,non-fullerene acceptors,side-chain conjugation,photovoltaic performance,fluorination
更新于2025-09-16 10:30:52
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Enhancing charge mobilities in self-assembled Na?ˉI halogen bonded organic semiconductors: A design approach based on experimental and computational perspectives
摘要： Charge transport in pyridine-ethynyliodophenyl supramolecules that involve intermolecular halogen bonding is studied by a combined experimental and computational approach. Selective fluorination of the molecules determines their crystallization pattern and is found to potentially increase the charge mobilities in the crystal. We report the synthesis of the molecules, full chemical characterization and resolved crystal structures. Computational analysis of the charge transport is provided to understand at the molecular level the structure-function relationships determining the charge mobilities. Combination of selective fluorination, halogen bonding motif and increased π system is highlighted as bearing the potential to achieve both enhanced hole and electron mobilities.
关键词： Selective fluorination and phenylation,Hole and electron mobility,Halogen bonding,Organic semiconductors,Charge transport,Density functional theory
更新于2025-09-16 10:30:52
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13.34% Efficiency Nonfullerene All-Small-Molecule Organic Solar Cells Enabled by Modulating Crystallinity of Donors via a Fluorination Strategy
摘要： Nonfullerene all-small-molecule organic solar cells (NFSM-OSCs) have shown a promising potential towards the commercialization of OSCs, owing to their unique advantages of high purity, easy synthesis and good reproducibility. However, great challenges in the modulation of phase separation morphology have limited their future development. Herein, two novel small molecular donors of BTEC-1F and BTEC-2F, derived from the small molecule DCAO3TBDTT, were designed and synthesized. While using Y6 as the acceptor, the devices based on non-fluorinated DCAO3TBDTT showed an open circuit voltage (Voc) of 0.804 V and a power conversion efficiency (PCE) of 10.64%. Mono-fluorinated BTEC-1F showed an increased Voc of 0.870 V and a PCE of 11.33%. More impressively, the fill factor (FF) of di-fluorinated BTEC-2F based NFSM-OSC was largely improved to 72.35% resulting in an impressive PCE of 13.34%, which was much higher than that of BTEC-1F (61.35%) and DCAO3TBDTT (60.95%). To the best of our knowledge, this is the highest reported PCE to date for NFSM-OSCs. BTEC-2F depicted a more compact molecular stacking and a lower crystallinity as revealed from characterization studies, which was beneficial for enhancing phase separation and carrier transport. Those results demonstrated an effective strategy to improve the performance of NFSM-OSCs via fluorination of small molecular donors and modulation of crystallinity deviation between donors and acceptors.
关键词： morphology,all-small-molecule organic solar cells,crystallinity,fluorination,orientation modulation
更新于2025-09-12 10:27:22
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13.34% Efficiency Nonfullerene All‐Small‐Molecule Organic Solar Cells Enabled by Modulating Crystallinity of Donors via a Fluorination Strategy
摘要： Nonfullerene all-small-molecule organic solar cells (NFSM-OSCs) have shown a promising potential towards the commercialization of OSCs, owing to their unique advantages of high purity, easy synthesis and good reproducibility. However, great challenges in the modulation of phase separation morphology have limited their future development. Herein, two novel small molecular donors of BTEC-1F and BTEC-2F, derived from the small molecule DCAO3TBDTT, were designed and synthesized. While using Y6 as the acceptor, the devices based on non-fluorinated DCAO3TBDTT showed an open circuit voltage (Voc) of 0.804 V and a power conversion efficiency (PCE) of 10.64%. Mono-fluorinated BTEC-1F showed an increased Voc of 0.870 V and a PCE of 11.33%. More impressively, the fill factor (FF) of di-fluorinated BTEC-2F based NFSM-OSC was largely improved to 72.35% resulting in an impressive PCE of 13.34%, which was much higher than that of BTEC-1F (61.35%) and DCAO3TBDTT (60.95%). To the best of our knowledge, this is the highest reported PCE to date for NFSM-OSCs. BTEC-2F depicted a more compact molecular stacking and a lower crystallinity as revealed from characterization studies, which was beneficial for enhancing phase separation and carrier transport. Those results demonstrated an effective strategy to improve the performance of NFSM-OSCs via fluorination of small molecular donors and modulation of crystallinity deviation between donors and acceptors.
关键词： morphology,all-small-molecule organic solar cells,crystallinity,fluorination,orientation modulation
更新于2025-09-12 10:27:22
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Di‐fluorinated Oligothiophenes for High‐Efficiency All‐Small‐Molecule Organic Solar Cells: Positional Isomeric Effect of Fluorine Substitution on Performance Variations
摘要： Three symmetrically di-fluorinated organic semiconductors (namely D5T2F-P, D5T2F-S, and D5T2F-T) containing rhodanine-flanked pentathiophene structures are synthesized and used as donors in all-small-molecule organic solar cells (ASM-OSCs) prepared with the small-molecule acceptor 2,2'-((2Z,2'Z)-((4,4,9,9-tetrahexyl-4,9-dihydro-s-indaceno[1,2-b:5,6-b']dithiophene-2,7-diyl)bis(methanylylidene))bis(5,6-difluoro-3-oxo-2,3-dihydro-1H-indene-2,1-diylidene))dimalononitrile (IDIC-4F). The different substitutional positions of the fluorine atoms (-F) in the conjugated backbone of the donor molecule leads to various material and photovoltaic properties being exhibited. Among the three isomers, the centrally-fluorinated D5T2F-P exhibits a redshifted absorption spectrum, downshifted highest occupied molecular orbital (HOMO) energy level, and improved miscibility with IDIC-4F in the blend films, all of which result in superior device performance. The power conversion efficiency (PCE) of the ASM-OSCs based on D5T2F-P:IDIC-4F reaches the impressive value of 9.36% with an open-circuit voltage (VOC) value of 0.86 V and a short-circuit current density (JSC) value of 16.94 mA/cm2, while those of D5T2F-S (6.11%) and D5T2F-T (5.42%) are much lower. In comparison, an ASM-OSC based on the non-fluorinated analogue DRCN5T fabricated under the same conditions exhibits poorer performance (8.03% with IDIC-4F), revealing a 16% enhancement in PCE achieved through backbone fluorination. To the best of our knowledge, the PCE of 9.36% is one of the highest efficiencies of oligothiophene-based ASM-OSCs reported in the literature to date.
关键词： organic solar cells,binding energy,small molecule donors,fluorination,non-fullerene
更新于2025-09-12 10:27:22
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Fluorination of pyrene-based organic semiconductors enhances the performance of light emitting diodes and halide perovskite solar cells
摘要： In this work, a fluorinated pyrene-based organic semiconductor (L-F) has been designed and synthesized starting from a low-cost pyrene core functionalized with triphenilamine substituents at 1,3,6,8 positions (L-H), obtained via Suzuki coupling reactions. Its performance when used as green emitter in organic light emitting diodes (OLEDs) or as dopant-free hole-transporting material (HTM) in halide perovskite solar cells (PSCs) is higher than the L-H counterpart, in spite of its lower bulk hole-mobility (7.0 x 10-6 cm2/Vs) with respect to L-H (1.9 x 10-4 cm2/Vs). In fact, the OLED devices based on L-F active layer showed excellent green emission (brightness and current efficiency were1759.8 cd/m2 and 3.7 cd/A, respectively) at a 4.5 V turn-on voltage. When the molecules were employed as a dopant-free HTM in PSCs, L-F led to a power conversion efficiency (PCE) and open circuit voltage (Voc) of 5.9 % and 1.07 V, respectively, thus outperforming those of corresponding devices based on L-H (PCE = 5.0% and Voc = 0.87 V) under similar experimental conditions (AM 1.5G and 100 mW cm2). We attribute the enhancements of L-F-based optoelectronic devices (OLEDs and PSCs) to the observed better quality of theL-F films. The promising performance of L-F indicates that fluorination of small molecules can be an effective strategy to achieve low-cost and high-performing materials for energy harvesting and display-based organic electronic devices.
关键词： pyrene,perovskite solar cells,hole transporting material,triphenylamine,fluorination,dopant-free,organic light emitting diodes
更新于2025-09-12 10:27:22
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Enhancing phase separation with a conformation-locked nonfullerene acceptor for over 14.4% efficiency solar cells
摘要： To fine-tune the morphology and miscibility of the active layer of organic solar cells (OSCs), the molecular backbone design and sidechain control are necessary but complex and challenging for acceptor–donor–acceptor type nonfullerene acceptors. In this work, both fluorination on accepting ends and sidechain modification on the central donating core were optimized for the design of fused-ring electron acceptors (FREAs). The sidechain-locked conformation finely modulates the molecular energy levels and improves the miscibility with weakened structural order. Fluorination effectively enhances the crystallinity to afford an enlarged phase separation and higher domain purity. Benefiting from their synergistic effects, the as-designed ITC6-4F when blended with the PM7 polymer donor enables an impressive power conversion efficiency of 14.47% with a high VOC of 0.90 V and improved FF of 74.31%, which is much higher than those of the devices based on reference FREAs without fluorination (8.21%) or conformation lock (12.48%). Our results demonstrate that enhancing phase separation with a conformation-locked nonfullerene acceptor could be an effective way for further improving the related performance of OSCs.
关键词： nonfullerene acceptors,organic solar cells,fluorination,power conversion efficiency,phase separation
更新于2025-09-12 10:27:22
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Understanding the Impact of Side-chain on Photovoltaic Performance in Efficient All-polymer Solar Cells
摘要： In order to understand the impact of side-chain on photovoltaic performance and explore efficient All-polymer solar cells, chemical modifications on donor-acceptor based polymers containing benzo[1,2-b:4,5-b’]dithiophene (BDT) and thieno[3,4-c]pyrrole-4,6-dione (TPD) backbones were performed. Via side-chain fluorination, the molecular design resulted in lower highest occupied molecular orbital (HOMO) energy levels and enhanced backbone planarity. The intermolecular packing and solid-state ordering were found to significantly improve. These factors are considered as key influences for carrier transport. In contrast, introducing a bulky alkylthio substituent group was found to slightly distort the polymer backbone. As a result of the lower HOMO level, PTF8 exhibits an improved open circuit voltage (Voc) compared to the template polymer PT8. However, due to the increased crystallinity and aggregation, PTF8 and PTS8 experience an unfavorable phase separation in polymer-polymer bulk heterojunction blends, hindering the PCE to about 4%. Through introducing alkylthio side-chains and fluorination, the polymer PTFS8 exhibits an extremely low HOMO level (-5.73 eV). These reduced HOMO level limits charge separation between the donor and acceptor polymers. Without any fluorination and alkylthio side-chains, the wide bandgap polymer PT8 exhibits desired HOMO energy levels and crystallinity, delivering a best PCE of 8% together with a high Voc of 1.05 V, displaying its great potential for applications in efficient all-polymer optoelectronic devices.
关键词： BDT-TPD backbone,side-chain,fluorination,All-polymer solar cells,alkylthio substitution,photovoltaic performance
更新于2025-09-12 10:27:22
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Adhesion of Single-walled Carbon Nanotube Thin Films with Different Materials
摘要： Single-walled carbon nanotubes (SWCNTs) possess extraordinary physical and chemical properties. Thin films of randomly oriented SWCNTs have great potential in many opto-electro-mechanical applications. However, good adhesion of SWCNT films with a substrate material is pivotal for their practical use. Here, for the first time we systematically investigate the adhesion properties of SWCNT thin films with commonly used substrates such as glass (SiO2), indium tin oxide (ITO), crystalline silicon (C-Si), amorphous silicon (a-Si:H), zirconium oxide (ZrO2), platinum (Pt), polydimethylsiloxane (PDMS), and SWCNTs for self-adhesion using atomic force microscopy. By comparing the results obtained in air and inert Ar atmospheres we observed a great contribution of the surface state of the materials on their adhesion properties. We found that the SWCNT thin films have higher adhesion in an inert atmosphere. The adhesion in the air can be greatly improved by a fluorination process. Experimental and theoretical analyses suggest that adhesion depends on the atmospheric conditions and surface functionalization.
关键词： adhesion energy,inert atmosphere,Single-walled carbon nanotubes,fluorination,ambient conditions,thin films
更新于2025-09-12 10:27:22