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Asymmetric Siloxane-Functional Side Chains Enable High-Performance Donor Copolymers for Photovoltaic Applications
摘要： In this work, three benzodithiophene (BDT)-benzotriazole (BTA) alternated wide bandgap (WBG) copolymers attaching symmetric or asymmetric conjugated side chains, namely PDBTFBTA-2T, PBDTFTBA-TSi and PBDTFBTA-2Si, were developed for efficient nonfullerene polymer solar cells. The symmetry effect of the side chains was investigated in detail on the overall properties of these donor polymers. The results demonstrated that the introduced siloxane functional groups showed less effect on the absorptions and frontier orbital levels of the prepared polymers but had significant effect on the miscibility between these polymer donors and nonfullerene acceptor. If increasing the content of siloxane functional groups, the miscibility of the polymer donors and Y6 would be improved, leading to the decreased domain size and more mixed domains. Interestingly, the active blend based on PBDTFTBA-TSi with asymmetric side chains exhibited more balanced miscibility, carrier mobility and phase separation, benefiting exciton diffusion and dissociation. Therefore, a champion power conversion efficiency (PCE) of 14.18% was achieved finally in PBDTFTBA-TSi devices, which was 20.6% and 19.0% higher than the symmetric counterparts of PBTFBTA-2T devices (PCE = 11.76%) and PBDTFBTA-2Si devices (PCE = 11.92%), respectively. This work highlights that the asymmetric side chain engineering based on siloxane functional groups is a promising design strategy for high-performance polymer donor semiconductors.
关键词： molecular design strategy,nonfullerene polymer solar cells,siloxane functional group,wide bandgap copolymers,asymmetric side chains
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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A New Wide Bandgap Donor Polymer for Efficient Nonfullerene Organic Solar Cells with a Large Open‐Circuit Voltage
摘要： Significant progress has been made in nonfullerene small molecule acceptors (NF-SMAs) that leads to a consistent increase of power conversion efficiency (PCE) of nonfullerene organic solar cells (NF-OSCs). To achieve better compatibility with high-performance NF-SMAs, the direction of molecular design for donor polymers is toward wide bandgap (WBG), tailored properties, and preferentially ecofriendly processability for device fabrication. Here, a weak acceptor unit, methyl 2,5-dibromo-4-fluorothiophene-3-carboxylate (FE-T), is synthesized and copolymerized with benzo[1,2-b:4,5-b′]-dithiophene (BDT) to afford a series of nonhalogenated solvent processable WBG polymers P1-P3 with a distinct side chain on FE-T. The incorporation of FE-T leads to polymers with a deep highest occupied molecular orbital (HOMO) level of ?5.60?5.70 eV, a complementary absorption to NF-SMAs, and a planar molecular conformation. When combined with the narrow bandgap acceptor ITIC-Th, the solar cell based on P1 with the shortest methyl chain on FE-T achieves a PCE of 11.39% with a large Voc of 1.01 V and a Jsc of 17.89 mA cm?2. Moreover, a PCE of 12.11% is attained for ternary cells based on WBG P1, narrow bandgap PTB7-Th, and acceptor IEICO-4F. These results demonstrate that the new FE-T is a highly promising acceptor unit to construct WBG polymers for efficient NF-OSCs.
关键词： complementary absorption,wide bandgap,donor polymers,nonfullerene organic solar cells,nonhalogenated solvents
更新于2025-09-19 17:13:59
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17.1% Efficient Singlea??Junction Organic Solar Cells Enabled by na??Type Doping of the Bulka??Heterojunction
摘要： Molecular doping is often used in organic semiconductors to tune their (opto)electronic properties. Despite its versatility, however, its application in organic photovoltaics (OPVs) remains limited and restricted to p-type dopants. In an effort to control the charge transport within the bulk-heterojunction (BHJ) of OPVs, the n-type dopant benzyl viologen (BV) is incorporated in a BHJ composed of the donor polymer PM6 and the small-molecule acceptor IT-4F. The power conversion efficiency (PCE) of the cells is found to increase from 13.2% to 14.4% upon addition of 0.004 wt% BV. Analysis of the photoactive materials and devices reveals that BV acts simultaneously as n-type dopant and microstructure modifier for the BHJ. Under optimal BV concentrations, these synergistic effects result in balanced hole and electron mobilities, higher absorption coefficients and increased charge-carrier density within the BHJ, while significantly extending the cells’ shelf-lifetime. The n-type doping strategy is applied to five additional BHJ systems, for which similarly remarkable performance improvements are obtained. OPVs of particular interest are based on the ternary PM6:Y6:PC71BM:BV(0.004 wt%) blend for which a maximum PCE of 17.1%, is obtained. The effectiveness of the n-doping strategy highlights electron transport in NFA-based OPVs as being a key issue.
关键词： nonfullerene acceptors,molecular doping,additives,organic photovoltaics
更新于2025-09-19 17:13:59
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17.1%-Efficiency organic photovoltaic cell enabled with two higher-LUMO-level acceptor guests as the quaternary strategy
摘要： Quaternary blended organic solar cells utilize four blended material components (one donor plus three acceptors, two donors and two acceptors, or three donors plus one acceptor) as the active layer materials. The use of four material components allows us to have more material selections and more mechanism choices to improve the photon-to-electron conversion efficiency. In this contribution, we present a new case of quaternary material system, that shows 17.1% efficiency obtained by adding IDIC and PC71BM as the guest acceptors of the host binary of PM6:Y6. The lowest unoccupied molecular orbital (LUMO) levels of IDIC and PC71BM are both higher than that of Y6, which is one reason to obtain increased open-circuit voltage (Voc) in the quaternary device. Upon introduction of IDIC and PC71BM as the acceptor guests, the hole and electron mobilities are both increased, which contributes to the increased short-circuit current-density (Jsc). Effects of the weight ratios of the three acceptor components are investigated, which demonstrates that the increased hole and electron mobilities, the accelerated hole-transfer, and the reduced monomolecular recombination are the factors contributing to the increased Jsc and fill-factor. This case of quaternary device demonstrates the applicability of the quaternary strategy in increasing the device functions and hence the efficiencies in the field of organic photovoltaic cells.
关键词： small-molecule acceptor,organic photovoltaic,quaternary solar cell,nonfullerene,fullerene
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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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
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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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Critical Role of Polymer Aggregation and Miscibility in Nonfullerenea??Based Organic Photovoltaics
摘要： Understanding the correlation between polymer aggregation, miscibility, and device performance is important to establish a set of chemistry design rules for donor polymers with nonfullerene acceptors (NFAs). Employing a donor polymer with strong temperature-dependent aggregation, namely PffBT4T-2OD [poly[(5,6-difluoro-2,1,3-benzothiadiazol-4,7-diyl)-alt-(3,3″′-di(2-octyldodecyl)-2,2′;5′,2″;5″,2″′-quaterthiophen-5,5-diyl)], also known as PCE-11 as a base polymer, five copolymer derivatives having a different thiophene linker composition are blended with the common NFA O-IDTBR to investigate their photovoltaic performance. While the donor polymers have similar optoelectronic properties, it is found that the device power conversion efficiency changes drastically from 1.8% to 8.7% as a function of thiophene content in the donor polymer. Results of structural characterization show that polymer aggregation and miscibility with O-IDTBR are a strong function of the chemical composition, leading to different donor–acceptor blend morphology. Polymers having a strong tendency to aggregate are found to undergo fast aggregation prior to liquid–liquid phase separation and have a higher miscibility with NFA. These properties result in smaller mixed donor–acceptor domains, stronger PL quenching, and more efficient exciton dissociation in the resulting cells. This work indicates the importance of both polymer aggregation and donor–acceptor interaction on the formation of bulk heterojunctions in polymer:NFA blends.
关键词： nonfullerene acceptors,charge transport,morphology,charge generation,polymer aggregation
更新于2025-09-16 10:30:52