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Significantly enhanced electron transport of nonfullerene acceptor in blend film with high hole mobility polymer of high molecular weight: thick-film nonfullerene polymer solar cells showing high fill factor
摘要： Overcoming fill factor (FF) decay in thick fullerene active layers has been demonstrated with high hole mobility (μh) polymers. However, this issue remains as a challenge for thick active layers with nonfullerene acceptors. Here we demonstrate high FF and highly efficient nonfullerene based thick active layer with high μh polymer as the donor. Its relatively balanced hole and electron transports with a μh/μe ratio of 4.42 in 320 nm thick blend film are realized by the high molecular weight polymer induced higher electron mobility (μe approaching 1×10?3 cm2/(V s)) for the blend film. Relative to the pristine IEICO-4F nonfullerene film, 8 times increased μe for the blend film corresponds to closer interdigitation of IEICO-4F lamella and higher order face-on orientation of in-plain (200) peak of IEICO-4F molecules, which are very helpful for electron transport. As a result, solar cells with 320 nm thick binary nonfullerene active layers show outstanding FF over 70% and power conversion efficiency of 13.2%, a breakthrough for a high μh polymer as the donor. Our results suggest that high μh polymer donors are promising candidates for nonfullerene based polymer solar cells.
关键词： nonfullerene acceptor,thick-film polymer solar cells,fill factor,electron transport,high hole mobility polymer
更新于2025-09-23 15:21:01
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Improving the Electron Mobility of ITIC by End-Group Modulation: The Role of Fluorination and π-Extension
摘要： Nonfullerene organic solar cells (OSCs) using ITIC derivatives as electron acceptors have achieved power conversion efficiencies up to 14%, yet optimal active-layer thicknesses are still limited to (cid:1)100 nm, ascribed mainly to the (cid:3)4 cm2/Vs) of these acceptors. Because of the large steric hindrance of the bulky side chains on the fused-ring core, ITIC favors a local π–π stacking between the electron-withdrawing end groups (IC), which provides the main electron transport channel across the bulk volume. Here, the influence of different fluoro-substituted and π-extended (i.e., benzene-fused) positions in the phenyl moiety of IC on the electron transport properties is systematically investigated by multiscale theoretical simulations. It is found that the electron mobility can be remarkablely improved by proper fluorination and π-extension, especially by π-extension, due to the lower reorganization energy and stronger end-group π-π interaction. Moreover, a judicious combination of π-extension and fluorination can lead to a nearly six-fold increase of the electron mobility with respect to ITIC. This work shows that the electron mobility of A-D-A nonfullerene acceptors can be effectively improved by end-group engineering, paving the way toward higher-performance organic solar cells.
关键词： electron mobility,molecular packing,nonfullerene acceptor,end-group engineering
更新于2025-09-23 15:21:01
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Delocalization boosts charge separation in organic solar cells
摘要： Organic solar cells (OSCs) utilizing π-conjugated polymers have attracted widespread interest over the past three decades because of their potential advantages, including low weight, thin film flexibility, and low-cost manufacturing. However, their power conversion efficiency (PCE) has been far below that of inorganic analogs. Geminate recombination of charge transfer excitons is a major loss process in OSCs. This paper reviews our recent progress in using transient absorption spectroscopy to understand geminate recombination in bulk heterojunction OSCs, including the impact of polymer crystallinity on charge generation and dissociation mechanisms in nonfullerene acceptor-based OSCs. The first example of a high PCE with a small photon energy loss is also presented. The importance of delocalization of the charge wave function to suppress geminate recombination is highlighted by this focus review.
关键词： Polymer crystallinity,Power conversion efficiency,Organic solar cells,Transient absorption spectroscopy,Dissociation mechanisms,Photon energy loss,π-conjugated polymers,Charge generation,Nonfullerene acceptor,Geminate recombination
更新于2025-09-23 15:19:57
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A Naphthodithiophene-Based Nonfullerene Acceptor for High-Performance Polymer Solar Cells with a Small Energy Loss
摘要： A Naphthodithiophene-Based Nonfullerene Acceptor for High-Performance Polymer Solar Cells with a Small Energy Loss
关键词： energy loss,intramolecular noncovalent interaction,nonfullerene acceptor,organic solar cell
更新于2025-09-23 15:19:57
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High performance and stable nonfullerene acceptor-based organic solar cells for indoor to outdoor light
摘要： We synthesized a donor polymer of bis(2-ethylhexyl)thiophene-substituted benzodithiophene (BDT-Th) and 1,3-bis(2-ethylhexyl)-5,7-di(thiophene-2-yl)benzo[1,2-c:4,5-c′]dithiophene-4,8-dione, for which the BDT-Th unit includes chlorine and sulfur-bridged 2-ethylhexyl in the thiophene side group. When compared with PBDB-TF, which includes fluorine and 2-ethylhexyl in BDT-Th, PBDB-TSCl shows more efficient exciton dissociation and charge-generation, which is probably because large dipole moment changes from ground to excited states lead to reduced exciton binding energy. Consequently, despite small donor-acceptor interface in the bulk-heterojunction (BHJ) film, PBDB-TSCl achieves higher photovoltaic performance than PBDB-TF under various light intensities; PBDB-TSCl achieved higher efficiency of 13.13% than 12.12% of PBDB-TF under 1 sun illumination. Moreover, PBDB-TSCl showed the highest efficiency of 21.53% with fill factor (FF) of 76.29% under a 500 lux fluorescence lamp, whereas PBDB-TF has lower efficiency of 15.57% with FF of 65.25%. Furthermore, the PBDB-TSCl device shows improved thermal stability due to more stabilized morphology of its BHJ film.
关键词： indoor light,nonfullerene acceptor,outdoor light,organic solar cells,thermal stability,photovoltaic performance
更新于2025-09-19 17:13:59
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Highly efficient organic photovoltaics with enhanced stability through the formation of doping-induced stable interfaces
摘要： Flexible organic photovoltaics (OPVs) are promising power sources for wearable electronics. However, it is challenging to simultaneously achieve high efficiency as well as good stability under various stresses. Herein, we demonstrate the fabrication of highly efficient (efficiency, 13.2%) and stable OPVs based on nonfullerene blends by a single-step postannealing treatment. The device performance decreases dramatically after annealing at 90 °C and is fully recovered after annealing at 150 °C. Glass-encapsulated annealed OPVs show good environmental stability with 4.8% loss in efficiency after 4,736 h and an estimated T80 lifetime (80% of the initial power conversion efficiency) of over 20,750 h in the dark under ambient condition and T80 lifetime of 1,050 h at 85 °C and 30% relative humidity. This environmental stability is enabled by the synergetic effect of the stable morphology of donor/acceptor blends and thermally stabilized interfaces due to doping. Furthermore, the high efficiency and good stability are almost 100% retained in ultraflexible OPVs and minimodules which are mechanically robust and have long-term operation capability and thus are promising for future self-powered and wearable electronics.
关键词： nonfullerene acceptor,environmental stability,ultraflexible devices,organic photovoltaics,high efficiency
更新于2025-09-19 17:13:59
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Secondary Bonds Modifying Conjugatea??Blocked Linkages of Biomassa??Derived Lignin to Form Electron Transfer 3D Networks for Efficiency Exceeding 16% Nonfullerene Organic Solar Cells
摘要： Fabricating high-efficient electron transporting interfacial layers (ETLs) with isotropic features is highly desired for all-directional electron transfer/collection from an anisotropic active layer, achieving excellent power conversion efficiency (PCEs) on nonfullerene acceptor (NFA) organic solar cells (OSCs). The complicated synthesis and cost-consumption in exploring versatile materials arouse great interest in the development of binary-doping interlayers without phase separation and flexible manipulation. Herein, for the first time, a novel cathode interfacial layer based on biomass-derived demethylated kraft lignin (DMeKL) is proposed. Features of multiple phenolic-hydroxyl (PhOH) and uniform-distributed render DMeKL to exhibit an excellent bonding capacity with amino terminal substituted perylene diiminde (PDIN), and successfully form a high-efficient isotropic electron transfer 3D network. Synchronously, secondary bonds completely modify conjugate-blocked linkages of DMeKL, significantly enhance the electron transporting performance on cross-section and vertical-sections, and repair the contact of PDIN with active layer. The DMeKL/PDIN-based 3D-network exhibits well-matched work function (WF) (–4.34 eV) with cathode (–4.30 eV) and energy level of electron acceptor (–4.11 eV). DMeKL/PDIN-based NFAs-OSC shows excellent short-circuit current density (26.61 mA cm–2) and PCE (16.02%) beyond the classic PDIN-based NFA-OSC (25.64 mA cm–2, 15.41%), which is the highest PCEs among biomaterials interlayers. The results supply a novel method to achieve high-efficient cathode interlayer for NFAs-OSCs.
关键词： secondary bonds,nonfullerene acceptor organic solar cells,electron transfer 3D network,biomass-derived lignin,power conversion efficiency
更新于2025-09-19 17:13:59
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Da??A Polymer with a Donor Backbone a?? Acceptora??sidea??chain Structure for Organic Solar Cells
摘要： We report the design, synthesis, and properties of a novel type of donor (D)-acceptor (A) polymer, poly(3-(([2,2':5',2''-terthiophen]-3-yl-5,5"-diyl)methylene)-1-(2-octyldodecyl)indolin-2-one) (PTIBT), with a donor backbone and acceptor side chains (Type II D-A polymer) as donor for organic solar cells (OSCs) as opposed to the conventional D-A polymers having both donor and acceptor units on backbone (Type I D-A polymers). PTIBT having a backbone consisting of thiophene donor units and side chains containing indolin-2-one acceptor units was synthesized very conveniently in three steps. This polymer has a high dielectric constant of 7.70, which is beneficial for the exciton diffusion and dissociation in the active blend layer in an OSC. In addition, PTIBT was found to have a low-lying HOMO energy level of -5.41 eV and a wide band gap of 1.80 eV in comparison to its counterpart Type I D-A polymer. In organic thin film transistors (OTFTs), PTIBT showed typical p-type semiconductor performance with hole mobilities of up to 1.81 × 10-2 cm2V-1s-1. When PTIBT and ITIC were used as donor and acceptor to form a blend active layer, the best OSC device showed a JSC of 15.19 mAcm-2, a VOC of 0.66 V, and a fill factor of 0.57, resulting in a power conversion efficiency (PCE) of up to 5.72%.
关键词： dielectric constant,novel D-A polymer donor,polythiophene,organic solar cells,nonfullerene acceptor
更新于2025-09-19 17:13:59
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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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Achieving high-performance non-halogenated nonfullerene acceptor-based organic solar cells with 13.7% efficiency <i>via</i> a synergistic strategy of an indacenodithieno[3,2- <i>b</i> ]selenophene core unit and non-halogenated thiophene-based terminal group
摘要： An outmost selenophene-functionalized electron-rich central core (indacenodithieno[3,2-b]selenophene) and a new non-halogenated A–D–A architecture non-fullerene small molecular acceptor (NF-SMA) (TSeTIC) based on indacenodithieno[3,2-b]selenophene as the central unit and thiophene-fused IC as a terminal group was designed and synthesized for high performance organic solar cells. In contrast to the similar NF-SMA (TTTIC) with an indacenodithieno[3,2-b]thiophene unit, TSeTIC exhibited a stronger and red-shifted absorption spectrum, higher highest occupied molecular orbital (HOMO) energy level, and enhanced electron mobility in neat thin films. Furthermore, a TSeTIC/PM6-based device presented higher hole/electron mobility, better phase separation features with favorable morphology, and higher charge dissociation and collection efficiency than a TTTIC/PM6-based device, resulting in remarkably improved Jsc and FF without sacrificing the Voc. Therefore, compared to the best PCE of 12.05% with an energy loss (Eloss) of 0.64 eV for the PM6/TTTIC device, the optimized PM6/TSeTIC device yields a significantly higher PCE of 13.71% with a higher FF of 75.9% and decreased Eloss of 0.60 eV. It is worth noting that the excellent PCE of 13.71% is the highest recorded for A–D–A structural NF-SMAs with thiophene-containing terminal groups for binary organic solar cells. These results demonstrate that the synergistic strategy of using an indacenodithieno[3,2-b]selenophene core unit and thiophene-containing IC end group is a promising avenue to enhance the PCE of non-halogenated NF-SMAs with high Voc and FF as well as low Eloss.
关键词： indacenodithieno[3,2-b]selenophene,non-halogenated nonfullerene acceptor,organic solar cells,synergistic strategy,thiophene-based terminal group
更新于2025-09-16 10:30:52