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Amorphous Polymer Acceptor Containing B ← N Units Matches Various Polymer Donors for All-Polymer Solar Cells
摘要： Polymer acceptors for high-efficiency all-polymer solar cells (all-PSCs) are generally semicrystalline. In this manuscript, we report an amorphous polymer acceptor, which matches well with a variety of polymer donors to produce efficient all-PSCs. The amorphous polymer acceptor (rr-PBN) is a regiorandom polymer consisting of alternating asymmetric B←N bridged thienylthiazole (BNTT) unit and pyridine-flanked diketopyrrolopyrrole (PyDPP) unit. It is amorphous in thin film because of its regiorandom structure and the large steric hindrance. rr-PBN shows deep LUMO/HOMO energy levels of ?3.71/?5.81 eV, strong sunlight harvesting capability and high electron mobility of 2.20 × 10?4 cm2 V?1 s?1. As a polymer acceptor, rr-PBN matches well with three commercially available polymer donors, J71, PTB7-Th, and PffBT4T-2OD to give excellent percolating bicontinuous network morphology in all-PSCs. We propose that the crystallization of polymer donors governs the film-forming process and dominates the phase separation morphology, leading to good phase separation morphology. The all-PSC devices all show power conversion efficiencies (PCEs) of 5.2?6.6%. This study provides a new direction to design polymer acceptors and a novel approach to control phase separation morphology of all-PSCs.
关键词： all-polymer solar cells,phase separation morphology,B←N units,amorphous polymer acceptor,power conversion efficiencies
更新于2025-09-11 14:15:04
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Fine-Tuning Semiconducting Polymer Self-Aggregation and Crystallinity Enables Optimal Morphology and High-Performance Printed All-Polymer Solar Cells
摘要： Polymer aggregation and crystallization behavior play a crucial role in the performance of all-polymer solar cells (all-PSCs). Gaining control over polymer self-assembly via molecular design to influence bulk-heterojunction active-layer morphology, however, remains challenging. Herein, we show a simple yet effective way to modulate the self-aggregation of the commonly used naphthalene diimide (NDI)-based acceptor polymer (N2200), by systematically replacing a certain amount of alkyl side-chains with compact bulky side-chains (CBS). Specifically, we have synthesized a series of random co-polymer (PNDI-CBSx) with different molar fractions (x = 0–1) of the CBS units and have found that both solution-phase aggregation and solid-state crystallinity of these acceptor polymers are progressively suppressed with increasing x as evidenced by UV-Vis absorption, photoluminescence (PL) spectroscopies, thermal analysis and grazing incidence X-ray scattering (GIWAXS) techniques. Importantly, compared to the highly self-aggregating N2200, photovoltaic results show that blending of more amorphous acceptor polymers with donor polymer (PBDB-T) can enable all-PSCs with significantly increased PCE (up to 8.5%). The higher short-circuit current density (Jsc) results from the smaller polymer phase-separation domain sizes as evidenced by PL quenching and resonant soft X-ray scattering (R-SoXS) analyses. Additionally, we show that the lower crystallinity of the active layer is less sensitive to the film deposition methods. Thus, the transition from spin-coating to solution coating can be easily achieved with no performance losses. On the other hand, decreasing aggregation and crystallinity of the acceptor polymer too much, reduces the photovoltaic performance as the donor phase-separation domain sizes increases. The highly amorphous acceptor polymers appear to induce formation of larger donor polymer crystallites. These results highlight the importance of a balanced aggregation strength between the donor and acceptor polymers to achieve high-performance all-PSCs with optimal active layer film-morphology.
关键词： morphology control,crystallinity,polymer aggregation,naphthalene diimide,all-polymer solar cells
更新于2025-09-11 14:15:04
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Surpassing the 10% efficiency milestone for 1-cm2 all-polymer solar cells
摘要： Naphthalenediimide-based n-type polymeric semiconductors are extensively used for constructing high-performance all-polymer solar cells (all-PSCs). For such all-polymer systems, charge recombination can be reduced by using thinner active layers, yet suffering insufficient near-infrared light harvesting from the polymeric acceptor. Conversely, increasing the layer thickness overcomes the light harvesting issue, but at the cost of severe charge recombination effects. Here we demonstrate that to manage light propagation within all-PSCs, a thick bulk-heterojunction film of approximately 350 nm is needed to effectively enhance photo-harvesting in the near-infrared region. To overcome the severe charge recombination in such a thick film, a non-halogenic additive is used to induce a well-ordered micro-structure that inherently suppresses recombination loss. The combined strategies of light management and delicate morphology optimization lead to a promising efficiency over 10% for thick-film all-PSCs with active area of 1 cm2, showing great promise for future large-scale production and application of all-PSCs.
关键词： all-polymer solar cells,light management,naphthalenediimide,thick-film,morphology optimization
更新于2025-09-11 14:15:04
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Backbone Fluorination of Polythiophenes Improves Device Performance of Non-Fullerene Polymer Solar Cells
摘要： Polythiophenes (PTs) are promising donor materials for the industrialization of polymer solar cells (PSCs) due to the merits of easy synthesis, low cost, and large-scale producibility. The rapid progress of non-fullerene acceptors requires the development of new PTs for use in non-fullerene PSCs. In this work, we present a set of PTs with different degree of backbone fluorination (P6T-F00, P6T-F50, P6T-F75, and P6T-F100) to investigate the effect of fluorination on the photovoltaic properties of PTs in non-fullerene PSCs. Upon increasing fluorine content, the PTs tend to have higher crystallinity, higher absorption coefficients, and enhanced relative dielectric constants. When blended with a non-fullerene acceptor EH-IDTBR, the blend films show increased photoluminescence quenching efficiency, reduced charge recombination loss, and extended charge carrier lifetime along with increasing fluorine content of PTs. These positive factors collectively result in dramatically improved power conversion efficiency from 4.3% for P6T-F00:EH-IDTBR to 7.3% for P6T-F100:EH-IDTBR, which is superior to the champion binary non-fullerene PSCs based on P3HT. Our results demonstrate that PTs are promising donor materials for non-fullerene PSCs via backbone fluorination.
关键词： polythiophenes,polymer solar cells,backbone fluorination,dielectric constant,non-fullerene acceptors
更新于2025-09-11 14:15:04
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Efficient non-fullerene polymer solar cells enabled by side-chain conjugated thieno[3,4-c]pyrrole-4,6-dione-based polymer and small molecular acceptors
摘要： The application of non-fullerene (NF) acceptors in bulk-heterojunction (BHJ) polymer solar cells (PSCs) is a promising approach to overcome the inherent drawbacks of fullerene derivatives-based acceptors. In PSCs, complementary absorption as well as matched molecular energy levels between the low bandgap acceptor-donor-acceptor (A-D-A) small molecular acceptor and medium/wide bandgap polymer donor is crucial to achieve high power conversion efficiency (PCE). Alternating polymers based on benzodithiophene (BDT) electron-donating segment and thieno[3,4-c]pyrrole-4,6-dione (TPD) electron-withdrawing segment own medium bandgap and low-lying highest occupied molecular orbital (HOMO) energy level, leading to presentable photovoltaic properties with fullerene derivatives. To probe into the performances of TPD-based polymers in NF-PSCs, two TPD-based polymers containing alkoxy or alkylthienyl modified benzo[1,2-b:4,5-b′]dithiophene (BDT) were synthesized and adopted as electron-donors and blended with A-D-A-type electron-acceptor 2,2′-[[6,6,12,12-tetrakis(4-hexylphenyl)-s-indacenodithieno[3,2-b]thiophene]methylidyne(3-oxo-1H-indene-2,1(3H)-diylidene)]]bis(propanedinitrile) (ITIC) to fabricate the corresponding photovoltaic devices. The two-dimensional conjugated polymer PBDTT-TPD shows enhanced extinction coefficient, deeper HOMO energy level and better hole transport performance, resulting in improved PCE of 6.17%. To further boost the performances of the polymers, a small molecular 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(3-oxo-2,3-dihydro-1H-indene-2,1-diylidene))dimalononitrile (IDIC) with down-shifted energy level was also used to blend with the two polymers in PSCs. Despite the open-circuit voltage (VOC) of the PBDTT-TPD:IDIC-based device is slightly decreased, the short-circuit current density (JSC) and fill factor (FF) are simultaneously improved, yielding an promising PCE of 7.15%. These results indicate that two-dimensional conjugated TPD-based polymers can be potential application as medium bandgap polymeric donor to match with small molecular acceptors having suitable molecular energy levels to get high efficiency in PSCs.
关键词： Non-fullerene acceptors,Thieno[3,4-c]pyrrole-4,6-dione,Energy level offsets,Polymer solar cells,Thermal annealing
更新于2025-09-11 14:15:04
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Synthesis and Photovoltaic Effect of Electron-Withdrawing Units for Low Band Gap Conjugated Polymers Bearing Bi(thienylenevinylene) Side Chains
摘要： A novel (E)-5-(2-(5-alkylthiothiophen-2-yl)vinyl)thien-2-yl (TVT)-comprising benzo[1,2-b:4,5-b’]dithiophene (BDT) derivative (BDT-TVT) was designed and synthetized to compose two donor-acceptor (D-A) typed copolymers (PBDT-TVT-ID and PBDT-TVT-DTNT) with the electron-withdrawing unit isoindigo (ID) and naphtho[1,2-c:5,6-c’]bis[1,2,5]thiadiazole (NT), respectively. PBDT-TVT-ID and PBDT-TVT-DTNT showed good thermal stability (360 °C), an absorption spectrum from 300 nm to 760 nm and a relatively low lying energy level of Highest Occupied Molecular Orbital (EHOMO) (?5.36 to –5.45 eV), which could obtain a large open-circuit voltage (Voc) from photovoltaic devices with PBDT-TVT-ID or PBDT-TVT-DTNT. The photovoltaic devices with ITO/PFN/polymers: PC71BM/MoO3/Ag structure were assembled and exhibited a good photovoltaic performance with a power conversion efficiency (PCE) of 4.09% (PBDT-TVT-ID) and 5.44% (PBDT-TVT-DTNT), respectively. The best PCE of a PBDT-TVT-DTNT/PC71BM-based device mainly originated from its wider absorption, higher hole mobility and favorable photoactive layer morphology.
关键词： polymer solar cells,photovoltaic property,benzo[1,2-b:4,5-b’]dithiophene,low band gap,bi(thienylenevinylene)
更新于2025-09-11 14:15:04
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Intrinsic Photo-degradation and Mechanism of Polymer Solar Cells: The crucial role of Non-fullerene Acceptor
摘要： The performances of polymer solar cells (PSCs) based on non-fullerene acceptors (NFAs) have improved remarkably in recent years, but such devices are insufficiently stable for practical applications. Here, we investigated the effects of NFAs on PSC long-term stability. We found that high performance PBDB-T:ITIC solar cells exhibit much lower stability than PTB7:PC71BM devices in the 1 sun light-soaking test; when compared with their initial performances, the performance of PTB7:PCBM-based solar cells remains above 60% for over 4000 h, whereas that of PBDB-T:ITIC-based devices is reduced to one fifth after 1000 h. We demonstrated that the ITIC-based PSCs exhibit poor photo-stability because ITIC at the interface of the ZnO/active film is readily decomposed by a photocatalytic reaction; this poor stability arises because the vinyl group of ITIC is chemically more vulnerable than the stable aromatic units in the organic active materials. The decomposition of ITIC results in the degradation of the electron transport properties of the active materials located close to ZnO, which leads to severe burn-in degradation and reduced FF and VOC under illumination. It is thus highly important to develop intrinsically stable organic materials composed of chemically stable building blocks in order to realize stable and high efficiency PSCs.
关键词： polymer solar cells,photocatalytic reaction,non-fullerene acceptors,photo-stability,ITIC
更新于2025-09-11 14:15:04
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Perylene Diimide‐Based Nonfullerene Polymer Solar Cells with over 11% Efficiency Fabricated by Smart Molecular Design and Supramolecular Morphology Optimization
摘要： A series of perylene diimide (PDI) derivatives, TPP-PDI, TPO-PDI, and TPS-PDI, are developed for nonfullerene polymer solar cells (NF-PSCs) by flaking three PDI skeletons around 3D central cores with different configurations and electronic states, such as triphenylphosphine (TPP), triphenylphosphine monoxide (TPO), and triphenylphosphine sulfide (TPS). These small-molecule acceptors have a “three-wing propeller” structure due to their similar backbones. By changing the electron density of phosphorus atoms through oxidation and sulfuration, the “folding-back” strength is decreased, resulting in a less twisted molecular conformation. The stronger electron-withdrawing ability of the oxygen atom affords TPO-PDI the least twisted conformation, which enhances the crystallinity of this complex. NF-PSCs based on PTTEA:TPO-PDI exhibit a high power conversion efficiency (PCE) of 8.65%. Ultimately, the joint “molecular lock” effect arising from OH???F and OH???OP supramolecular interactions is achieved by introducing 4,4′-biphenol as an additive, which successfully promotes fibril-like phase separation and blend morphology optimization to generate the highest PCE of 11.01%, which is currently the highest value recorded for NF-PSCs based on PDI acceptors.
关键词： triphenylphosphine oxide cores,nonfullerene polymer solar cells,molecular locks,hydrogen bonds,perylene diimide acceptors
更新于2025-09-11 14:15:04
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A Novel Carbazole Based Nonfullerene Acceptor for High‐Efficiency Polymer Solar Cells
摘要： Two novel nonfullerene acceptors 4TFIC-4F and 4TCIC-4F are designed based on fluorene and carbazole. Compared with 4TFIC-4F, 4TCIC-4F exhibited higher LUMO level and narrower optical bandgap. Therefore, Polymer solar cells based on PBDB-T-2Cl:4TCIC-4F achieve a high power conversion efficiency of 13.02%, which is the highest value for the carbazole-containing nonfullerene acceptors based devices.
关键词： Morphology,Nonfullerene acceptors,Donor core,Energy levels,Polymer solar cells
更新于2025-09-11 14:15:04
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Efficient Polymer Solar Cells Based on New Random Copolymers with Porphyrin‐Incorporated Side Chains
摘要： Two new wide bandgap block copolymers (PL1 and PL2) with porphyrin-incorporated side chains are designed and used as electron donors for solution-processed bulk heterojunction polymer solar cells. The photophysical, electrochemical, and photovoltaic properties, charge transport mobility and film morphology of these two block copolymers are investigated. Detailed investigations reveal that the different alkyl groups and electron-withdrawing substituents on the porphyrin pendant units have significant influence on the polymer solubility, absorption energy level, band gap, and charge separation in the bulk-heterojunction thin films, and thus the overall photovoltaic performances. Organic photovoltaic devices derived from these copolymers and ([6,6]-phenyl-C71-butyric acid methyl ester) (PC71BM) acceptor show the best power conversion efficiencies of 5.83% and 7.14%, respectively. These results show that the inclusion of a certain proportion of side chain porphyrin group as a pendant in the traditional donor-acceptor (D-A) type polymer can broaden the molecular absorption range and become a full-color absorbing molecule. The size of the porphyrin pendant also has an obvious effect on the properties of the molecule.
关键词： block copolymers,organic photovoltaics,polymer solar cells,bulk heterojunctions,porphyrin
更新于2025-09-11 14:15:04