Acceptor Polymers Research Articles

Design, Synthesis, and Application in OFET of a Quinoxaline-Based D-A Conjugated Polymer.

A novel alternating donor–acceptor polymer PQ1 is designed and synthesized by palladium-catalyzed Stille coupling between quinoxaline as an electron-deficient unit and indacenodithiophene (IDT) as electron-rich groups. Polymer PQ1 presents not only a strong intramolecular charge transfer effect, which is beneficial for the charge transport within single molecules but also a narrow electrochemical band gap and a high highest occupied molecular orbital (HOMO) energy level. In addition, the optical absorption study indicates that the PQ1 film exhibits good aggregation, which is an advantage for the charge transport between neighboring molecules. As a consequence, PQ1 presents p-type semiconductor properties with a high hole mobility of up to 0.12 cm2 V−1 s−1. This study reveals the great potential of quinoxaline-type chromophores in constructing novel organic semiconductors.

Intrinsically‐Stretchable, Efficient Organic Solar Cells Achieved by High‐Molecular‐Weight, Electro‐Active Polymer Acceptor Additives

AbstractOrganic solar cells (OSCs) are promising wearable/stretchable power sources, but the development of high‐performance intrinsically stretchable OSCs (IS‐OSCs) has rarely been reported. Herein, IS‐OSCs exhibiting high power conversion efficiencies (PCEs) (>12%) and excellent stretchability are developed by constructing efficient and mechanically robust active layers via the addition of a high‐molecular weight polymer acceptor (PA) to polymer donor:small‐molecule acceptor blends. PA addition significantly enhances the stretchability and PCEs of the blends as the long PA chains function as molecular bridges between different domains, effectively dissipating mechanical stresses and improving charge transport. The IS‐OSCs with 20 wt% PA content exhibit a high PCE of 11.7% and excellent stretchability, retaining 84% of the initial PCE after 100 cycles of repetitive stretching/releasing at a 15% strain. To the best of the authors’ knowledge, the device represents the best IS‐OSC performance reported to date in terms of PCE and stretchability, demonstrating the great potential of IS‐OSCs as an efficient and wearable power generator.

Fused perylene diimide-based polymeric acceptors with different π-conjugation and molecular conformation in all polymer solar cells

Two perylene diimide (PDI) based polymeric acceptors, PFPDIBT-TT2F and PFPDIT-TT2F, which consist of fused-PDI moieties (FPDIBT and FPDIT) and 3,3′-difluoro-2,2′-bithiophene (TT2F) units, has been designed and synthesized. Compared with the unfused-PDI polymer (PPDI-TT2F) as the control molecule, the influence of structural conformation and π-conjugation extension on the performance of all-polymer solar cells has been investigated. Due to both the extended π-conjugation and the torsional polymer skeleton, the device adopting PFPDIT-TT2F achieved an obviously improved PCE of 5.11% comparing with the devices using the other two polymeric acceptors. This study demonstrates that the fused PDIs bridged by a thiophene enables both extended π-conjugation and twisted molecular conformation, and the latter plays a dominant role in the improvement of device performance.

High-Performance All-Polymer Photodetectors Enabled by New Random Terpolymer Acceptor with Fine-Tuned Molecular Weight.

Reducing the dark current density and enhancing the overall performance of the device is the focal point in research for organic photodetectors. Two novel random terpolymers (P3 and P4) with different molecular weights are synthesized and evaluated as acceptors in bulk heterojunction (BHJ) polymer photodetectors. Compared with known acceptor materials, such as N2200 (P1) and F-N2200 (P2), polymer P4 has a lower lowest unoccupied molecular orbital (LUMO) energy level, favorable morphology, and good miscibility with a donor material J71, which leads to proper phase separation of the blend film and better dissociation of excitons and transport of carriers. Therefore, a considerably low dark current density (Jd) of 1.9 × 10-10 A/cm2 and a high specific detectivity (D*) of 1.8 × 1013 cm Hz1/2/W (also "Jones") at 580 nm under a -0.1 V bias are realized for the P4-based photodetector. More importantly, the device also exhibits a fast response speed (τr/τf = 1.24/1.87 μs) and a wide linear dynamic range (LDR) of 109.2 dB. This work demonstrates that high-performance all-polymer photodetectors with ideal morphology can be realized by random polymer acceptors with a fine-tuned molecular weight.

Improved Photovoltaic Performance of Ternary All-Polymer Solar Cells by Incorporating a New Y6-based Polymer Acceptor and PC61BM

Improved Photovoltaic Performance of Ternary All-Polymer Solar Cells by Incorporating a New Y6-based Polymer Acceptor and PC61BM

Vinylene-Inserted Asymmetric Polymer Acceptor with Absorption Approaching 1000 nm for Versatile Applications in All-Polymer Solar Cells and Photomultiplication-Type Polymeric Photodetectors.

The emerging polymerized small-molecule acceptors (PSMAs) with near-infrared (NIR) absorption have not only significantly boosted the power conversion efficiencies (PCEs) of all-polymer solar cells (all-PSCs) but have also exhibited great potential for sensitive NIR polymeric photodetectors (PPDs). However, there is no report regarding PSMAs with photo-response that can approach 1000 nm, which is an important criterion for applications in NIR-responsive all-PSCs and PPDs. Herein, by unidirectionally inserting vinylene segments into a selenophene-rich polymer backbone to improve the electron-donating strength and quinoidal character, an asymmetric PSMA, namely, PY3Se-1V, was developed, which showed an extensively red-shifted absorption approaching 1000 nm. The PBDB-T:PY3Se-1V-based binary all-PSCs achieve a decent PCE of 13.2% and a record-high photocurrent density of 25.9 mA cm-2 due to the significantly broadened photo-response and efficient photon-to-electron conversion. More encouragingly, narrowband photomultiplication (PM)-type PPDs based on poly(3-hexylthiophene-2,5-diyl) (P3HT):PY3Se-1V were developed, delivering an exceptionally high external quantum efficiency of 3680% and a responsivity of 28 A W-1 at an NIR peak of 960 nm under -50 V bias, which is reported for the first time in PM-type PPDs with a response approaching 1000 nm.

18.55% Efficiency Polymer Solar Cells Based on a Small Molecule Acceptor with Alkylthienyl Outer Side Chains and a Low-Cost Polymer Donor PTQ10

18.55% Efficiency Polymer Solar Cells Based on a Small Molecule Acceptor with Alkylthienyl Outer Side Chains and a Low-Cost Polymer Donor PTQ10

Effect of Isomerization of Linking Units on the Photovoltaic Performance of PSMA-Type Polymer Acceptors in All-Polymer Solar Cells

Effect of Isomerization of Linking Units on the Photovoltaic Performance of PSMA-Type Polymer Acceptors in All-Polymer Solar Cells

A Vinylene-Linker-Based Polymer Acceptor Featuring a Coplanar and Rigid Molecular Conformation Enables High-Performance All-Polymer Solar Cells with Over 17% Efficiency.

State-of-art Y-series polymer acceptors are typically based on a mono-thiophene linker, which can cause some twisted molecular conformations and thus limit the performance of all-polymer solar cells (all-PSCs). Here, a high-performance polymer acceptor based on vinylene linkers is reported, which leads to surprising changes in the polymers' molecular conformations, optoelectronic properties, and enhanced photovoltaic performance. It is found that the polymer acceptors based on thiophene or bithiophene linkers (PY-T-γ and PY-2T-γ) display significant molecular twisting between end-groups and linker units, while the vinylene-based polymer (PY-V-γ) exhibits a more coplanar and rigid molecular conformation. As a result, PY-V-γ demonstrates a better conjugation and tighter interchain stacking, which results in higher mobility and a reduced energetic disorder. Furthermore, detailed morphology investigations reveal that the PY-V-γ-based blend exhibits high domain purity and thus a better fill factor in its all-PSCs. With these, a higher efficiency of 17.1% is achieved in PY-V-γ-based all-PSCs, which is the highest efficiency reported for binary all-PSCs to date. This work demonstrates that the vinylene-linker is a superior unit to build polymer acceptors with more coplanar and rigid chain conformation, which is beneficial for polymer aggregation and efficient all-PSCs.

Developing Y-Branched Polymer Acceptor with 3D Architecture to Reconcile Between Crystallinity and Miscibility Yielding >15%Efficient All-Polymer Solar Cells.

In all‐polymer solar cells (all‐PSCs), there remains such a dilemma that obtains good miscibility and crystallinity simultaneously. Herein a new family of Y‐shape polymer acceptor, namely PYTT is developed, which is copolymerized from Y6 and benzotrithiophene units in three‐way directions. Benefiting from its high‐density end‐chains and extended π‐conjugation thanks to highly‐branched 3D architecture, PYTT displays better organic solubility despite much higher molecular weights, larger crystallinity, and tighter π‐stacking than the linear counterpart—PYT comprising Y6 and thiophene moieties, while showing identical optical absorption yet threefold higher photoluminescence intensity. In PYTT blend film with PM6 polymer donor, the interpenetrating nano‐fibrillar structures are formed with well‐intermixed polymeric domain sizes close to the exciton diffusion length, which is greatly conducive to exciton dissociation and charge transport in device. Consequently, PYTT‐based all‐PSCs exhibit all increased photovoltaic parameters, yielding a decent power conversion efficiency of 15.60%, which is ≈20% enhancement over PYT‐based device, along with low nonradiative loss of 0.221 meV.

Frontispiece: Polymer Acceptors for High‐Performance All‐Polymer Solar Cells

All-polymer solar cells show distinctive advantages over other types of organic solar cells, including superior mechanical flexibility and enhanced device stability. This review summarizes the progress of high-performance polymer acceptors based on the key electron-deficient building blocks developed recently, which drives the rapid improvement of power conversion efficiencies of all-polymer solar cells in the last couple of years. For more details, see the Review by K. Feng, X. Guo et al. (DOI: 10.1002/chem.202200222).

Suppressing non-radiative loss via a low-cost solvent additive enables high-stable all-polymer solar cells with 16.13% efficiency

The power conversion efficiency (PCE) of all-polymer solar cells (all-PSCs) has made a huge breakthrough in the past six years, but the PCE is far from the theoretical limit. A key reason for limiting the PCE of all-PSCs is the huge non-radiative loss,limitingopen-circuit voltage (VOC)and fill factor (FF) improvementfor all-PSCs. Tuning the chemical structure of the polymer donor and polymer acceptor, and designing suitable interfacial materials are the most common methods to improve theVOCand FF of all-PSCs, but this method is too costly because synthesizing new materials may be a repeated failure process. In this work, we realized a 16.13% PCE with boostedVOCof 0.86 V and FF of 76.02% for all-PSCs based on PBDB-T (poly[(2,6-(4,8-bis(5-(2-ethylhexyl)thiophen-2-yl)-benzo[1,2-b:4,5-b’]dithio-phene)) -alt-(5,5-(1′,3′-di-2-thienyl-5′,7′-bis(2-ethylhexyl)benzo[1′,2′-c:4′,5′-c’]di-thiophene-4,8 dione)]) and PYF-T via incorporating a low-cost solvent additive 1-chloronaphthalene (CN) into the processing solvent chlorobenzene.A range of device physical analysesindicate that CN additive can effectively suppress the non-radiative loss and energetic disorder in the device.Detailed blend film morphologyinvestigation highlight that CN additive promotes vertical phase separation and π-π stacking in PBDB-T:PYF-T blends during film drying processes. These observations exemplify the significance of CN additive as a tool for boostingVOCand FF of all-PSCs, which may initiate an extraordinary field for making solvent additive work in an intelligent way in all-PSCs.

Unraveling the Correlations between Mechanical Properties, Miscibility, and Film Microstructure in All‐Polymer Photovoltaic Cells

AbstractThe rapid development of low bandgap polymer acceptors has promoted the efficiency up to ≈17% for all‐polymer solar cells (all‐PSCs). Nevertheless, the polymeric blend film, core to the photoelectric conversion of all‐PSCs, has not been thoroughly understood in terms of the influence and regulatory factors of mechanical properties, which hinders the advances in flexible and wearable applications. Herein, a range of characterization methods is combined to investigate the mechanical properties, miscibility, and film microstructure of the blends based on several representative polymer donors (PTzBI‐Si, PTVT‐T, PM6 and PTQ10) and a benchmark polymer acceptor N2200, and to further reveal the miscibility‐property relationships of the miscibility property. The results stress that fracture behaviors and elastic moduli of these blends with varied compositions show different changing trends, which are affected by molecular interactions and aggregated structure of the blends. The elastic moduli of the four all‐polymer blends can be nicely predicted by different models that are deduced from macromolecular mechanics. Most crucially, the correlations between elastic modulus, morphology, and miscibility of all‐polymer blends are elucidated for the first time. The derived relationships is validated with another high‐efficiency blend and will be the key to the successful fabrication of mechanically robust and stretchable all‐PSCs with high efficiency.

Quasiplanar Heterojunction All‐Polymer Solar Cells: A Dual Approach to Stability

AbstractIn addition to efficiency, stability is another key factor in developing organic solar cells. The quasiplanar heterojunction (Q‐PHJ) structure, combining two pure layers as major and tiny nanoscale bulk heterojunction (BHJ) at interface, demonstrates superior device stability compared with BHJ devices. In this contribution, the polymer donor, PBQx‐H‐TF, and configurationally defined polymeric acceptor, PBTIC‐γ‐TSe are synthesized and used to fabricate bilayer devices by orthogonal solvents, the corresponding Q‐PHJ all‐polymer solar cells (all‐PSCs) deliver reliable stability with high efficiency. An encouraging PCE of 15.77% is achieved, which is the highest one among Q‐PHJ all‐PSCs with real‐bilayer structure. There is a major improvement over the 13.91% PCE in the BHJ device, and the carrier transport performance is improved substantially following the reduction of recombination in the Q‐PHJ all‐PSCs. Benefiting from the bilayer morphology, the stability of Q‐PHJ all‐PSCs has been greatly enhanced over that of the BHJ devices. The charge recombination process is also more serious in the aging BHJ compared with the aging Q‐PHJ all‐PSCs. This work inspires the application of Q‐PHJ in the preparation of high‐efficient all‐PSCs, but also provides guidance on the improvement of device stability from a dual approach of material and device engineering aspects.

Ternary organic solar cells with enhanced charge transfer and stability combining the advantages of polymer acceptors and fullerene acceptors

Organic solar cells (OSCs) based on highly efficient non-fullerene acceptors (NFAs) have recently developed rapidly, and achieved effective charge separation and high open-circuit voltage ( V OC ) under low driving force. Nonetheless, the low driving force inescapably reduces the short-circuit current ( J SC ) and potentially restricts the improvement of external quantum efficiency (EQE). Herein, we introduce the fullerene acceptor PC 71 BM into the efficient NFA system. And the PM6:PY-IT system is selected as a typical NFA system for its high V OC above 0.90 V. Benefiting from the deeper energy level, excellent electron transport characteristic, and unique spherical structure of PC 71 BM, the driving force for charge transfer is effectively improved. Accordingly, the ternary OSC based on PM6:PY-IT:PC 71 BM demonstrates a high efficiency of 16.36%, a much-enhanced J SC of 25.06 mA cm −2 , and the maximum EQE value is successfully increased to 87%, which is superior to binary OSC (efficiency of 14.84%, J SC of 23.10 mA cm −2 and maximum EQE value of 80%). Meanwhile, the introduction of PC 71 BM improves the molecular stacking structure, resulting in excellent stability in non-encapsulated ternary OSCs, which retain 80% initial efficiency after 6 h of continuous illumination treatment and 85% initial efficiency after 33 days of storage (the efficiencies decrease to 68% and 76% respectively in binary OSCs). In addition, similar conclusions can be drawn in another classical NFA system PM6:Y6, with an optimal efficiency of 17.49%. This work proves that PC 71 BM has unique advantages and great research potential in improving the driving force for charge transfer. • The highlights of this work can be summarized as follows: • The PC 71 BM was incorporated into the PM6:PY-IT system to enhance the driving force and construct efficient OSCs. • Benefiting from the enhanced driving force, the maximum EQE and J SC are significantly increased, and the V OC is 0.942 V. • The ternary OSC obtained an optimal efficiency of 16.36%, which is superior to binary OSC (efficiency of 14.84%). • The stability of the non-encapsulated optimized ternary device was improved by the incorporation of PC 71 BM.

Rational Regulation of the Molecular Aggregation Enables A Facile Blade-Coating Process of Large-area All-Polymer Solar Cells with Record Efficiency.

Developing robust materials is very critical and faces a big challenge for high-performance large-area all-polymer solar cells (all-PSCs) by printing methods. Herein, the authors combine the advantages of the terpolymerization strategy with the non-conjugated backbone strategy to regulate the molecular aggregation rationally during the film-forming printing process, facilitating a facile printing process for large-area all-PSCs. A series of terpolymer acceptors PYSe-Clx (x = 0, 10, 20, and 30) is also developed, which can effectively fine-tune the morphology and photoelectric properties of the active layer. The PBDB-T: PYSe-Cl20-based all-PSC delivers a significantly improved power cconversion efficiency (PCE) than the one with PBDB-T: PYSe (14.21%vs 12.45%). By addition of a small amount of non-conjugated polymer acceptor PTClo-Y, the ternary all-PSC reaches a PCE of 15.26%. More importantly, the regulation of molecular aggregation enables a facile blade-coating process of the large-area device. A record PCE of 13.81% for large-area devices (1.21cm2 ) is obtained, which is the highest value for large-area all-PSCs fabricated by blade-coating. The environmentally friendly solvent processed large-area device also obtains an excellent performance of 13.21%. This work provides a simple and effective molecular design strategy of robust materials for high-performance large-area all-PSCs by a printing process.

High‐Efficiency P3HT‐Based All‐Polymer Solar Cells with a Thermodynamically Miscible Polymer Acceptor

Poly(3‐hexylthiophene) (P3HT) is the most classical conjugated polymer for organic photovoltaics due to its low‐cost and synthetic scalability. However, P3HT‐based organic photovoltaics suffer from inferior device performance with respect to donor–acceptor copolymers. Particularly, the device performance of P3HT‐based all‐polymer solar cells (all‐PSCs) is rather poor due to the challenges in reaching ideal bulk‐heterojunction morphology. Herein, highly efficient P3HT‐based all‐PSCs by blending P3HT with a thermodynamic miscible polymer acceptor are reported. Among the three state‐of‐the‐art polymer acceptors (N2200, PYT, and DCNBT‐IDT), N2200 and PYT are thermodynamically immiscible with P3HT and thus led to excessive phase separation when blended with P3HT, whereas DCNBT‐IDT displayed proper thermodynamic miscibility with P3HT and generated the formation of well‐mixed fibrillary active layer morphology. As a result, a power conversion efficiency of 7.35% has been achieved by P3HT:DCNBT‐IDT blend, which is a new record for P3HT‐based all‐PSCs and largely higher than any previous results. Broad implication for further efficiency enhancement of P3HT‐based all‐PSCs is provided in the results and a promising pathway to realize highly efficient yet cost‐effective solar energy production is suggested.

Aggregation of Small Molecule and Polymer Acceptors with 2D-Fused Backbones in Organic Solar Cells

Aggregation of Small Molecule and Polymer Acceptors with 2D-Fused Backbones in Organic Solar Cells

Low-cost polymer acceptors with noncovalently fused-ring backbones for efficient all-polymer solar cells

Low-cost polymer acceptors with noncovalently fused-ring backbones for efficient all-polymer solar cells

Oligomeric Acceptor: A “Two‐in‐One” Strategy to Bridge Small Molecules and Polymers for Stable Solar Devices

AbstractOligomeric acceptors are expected to combine the advantages of both highly developed small molecular and polymeric acceptors. However, organic solar cells (OSCs) based on oligomers lag far behind due to their slow development and low diversity. Here, three oligomeric acceptors were produced through oligomerization of small molecules. The dimer dBTICγ‐EH achieved the best power conversion efficiencies (PCEs) of 14.48 % in bulk heterojunction devices and possessed a T80 (80 % of the initial PCE) lifetime of 1020 h under illumination, which were far better than that of small molecular and polymeric acceptors. More excitingly, it showed PCEs of 16.06 % in quasi‐planar heterojunction (Q‐PHJ) devices which is the highest value OSCs using oligomeric acceptors to date. These results suggest that oligomerization of small molecules is a promising strategy to achieve OSCs with optimized performance between the high efficiency and durable stability, and offer oligomeric materials a bright future in commercial applications.