Acceptor Polymers Research Articles

High‐Performance Binary All‐Polymer Solar Cells with Efficiency Over 18.3% Enabled by Tuning Phase Transition Kinetics

AbstractAll‐polymer solar cells (All‐PSCs) are considered to be the most promising candidates for realizing efficient and stable organic solar cells (OSCs). However, the challenge of controlling morphology has hindered the performance of All‐PSCs. Compared to small molecule acceptors, polymer acceptors play a more crucial role in obtaining an ideal morphology for All‐PSCs. The molecular weight of polymer acceptors is one of the key factors determining the morphological and mechanical properties as well as the interactions with donors. Herein, by using a monomer of PYIT (PYIT1) and PYITs with low (PYIT2) and high (PYIT3) molecular weights, the impact of molecular weight of the polymer acceptor is systematically investigated on the phase transition process, morphological, and photovoltaic properties. It is found that tuning the molecular weight effectively regulates the phase transition process of the polymer acceptor and its interaction with the polymer donor. This induces significant effects on the aggregation behaviors of the polymers. Appropriate molecular weight polymer acceptors can facilitate favorable phase separation morphology. With PBQx‐Cl as the donor and PYIT2 as acceptor, a high‐performance binary All‐PSC is achieved with an efficiency of 18.39%. This study provides deep insights into the performance enhancement of All‐PSCs through rational polymer acceptor design.

Active Control of Energy Transfer in Plasmonic Nanorod-Polyaniline Hybrids.

The hybridization of plasmonic energy and charge donors with polymeric acceptors is a possible means to overcome fast internal relaxation that limits potential photocatalytic applications for plasmonic nanomaterials. Polyaniline (PANI) readily hybridizes onto gold nanorods (AuNRs) and has been used for the sensitive monitoring of local refractive index changes. Here, we use single-particle spectroscopy to quantify a previously unreported plasmon damping mechanism in AuNR-PANI hybrids while actively tuning the PANI chemical structure. By eliminating contributions from heterogeneous line width broadening and refractive index changes, we identify efficient resonance energy transfer (RET) between AuNRs and PANI. We find that RET dominates the optical response in our AuNR-PANI hybrids during the dynamic tuning of the spectral overlap of the AuNR donor and PANI acceptor. Harnessing RET between plasmonic nanomaterials and an affordable and processable polymer such as PANI offers an alternate mechanism toward efficient photocatalysis with plasmonic nanoparticle antennas.

Triggering the Donor-Acceptor Phase Segregation with Solid Additives Enables 16.5% Efficiency in All-Polymer Solar Cells.

All-polymer solar cells have attracted considerable research interest due to their superior morphological stabilities, stretchability, and mechanical durability. However, the morphology optimization of the all-polymer bulk heterojunctions remains challenging due to the two long conjugated polymer chains, limiting its power conversion efficiency. Herein, we focus on the donor-acceptor phase segregation of an all-polymer active layer composed of PM6/PY-IT, a state-of-the-art all-polymer combination, by the introduction of volatile solid additives. Especially with 1,3-dibromo-5-chlorobenzene (DBCl) as the processing additive, we could effectively tune the miscibility between PM6 and PY-IT and thus optimize the phase segregation of the polymer donor and acceptor. Due to the synergetic effects on the favorable phase segregation and desired donor-acceptor distribution, the DBCl-treated devices feature the evident improvement of charge transport and collection, accompanied by the suppressed trap-assisted charge recombination. We consequently achieved a champion device efficiency of 16.5% (16.4% averaged), which is a 13% improvement compared with the control device without DBCl (14.6%). Our results highlight the importance of altering the miscibility of the polymer donor-acceptor pairs for practical applications of high-performance all-polymer solar cells.

NIR-absorbing polymer acceptor for efficient all-polymer solar cells with a record-high photocurrent of 26.5 ​mA ​cm−2

Achieving high short-circuit current density (JSC) to boost power conversion efficiency (PCE) of all-polymer solar cells (all-PSCs) is a major challenge, mainly due to the difficulty in developing high-performance near-infrared (NIR)-absorbing polymer acceptors. Herein, a new polymer acceptor named PY2Se–4F employing a Y-series small-molecule acceptor as the precursor is designed and synthesized. Thanks to its unique molecular backbone structure combining selenophene-fused central core and bi-fluorinated end-group, PY2Se–4F shows desirable NIR-absorption with a spectral onset approaching 1000 ​nm, which is beneficial for obtaining high JSC when matched with wide bandgap polymer donors such as PM6 and D18. For the binary all-PSCs, PM6:PY2Se–4F delivers a record-high JSC of 26.5 ​mA ​cm−2, which is superior to that of D18:PY2Se–4F, mainly due to stronger absorption in the range of 600–700 ​nm. In contrast, the D18:PY2Se–4F combination exhibits more favorable blend morphology, higher and more balanced charge-transporting, and less non-radiative energy loss compared with the PM6:PY2Se–4F. As a result, the D18:PY2Se–4F-based devices offer an improved PCE of 16.1 ​% with a JSC of 25.5 ​mA ​cm−2 and both higher photovoltage and fill factor, while the related PCE and JSC are ones of the top values among the reported binary all-PSCs. The results indicate that PY2Se–4F is a promising NIR-absorbing polymer acceptor for obtaining efficient all-PSCs with record-high JSC.

High Comprehensive Circularly Polarized Electroluminescence Performance Improved by Chiral Coassembled Host Materials

AbstractCircularly polarized organic light‐emitting diodes are of great significance in 3D displays. However, achieving circularly polarized electroluminescence (CP‐EL) simultaneously with a large dissymmetry factor (gEL) and high efficiency still remains a formidable challenge. Herein, a facile and efficient strategy is developed for improving the performance of CP‐EL devices using device emitting layers of chiral coassembled helix nanofiber host materials. Chiral coassembled helix nanofiber host materials ((S‐/R‐2Cz)0.2‐(PFpy)0.8) could be smartly constructed through intermolecular π–π stacking interactions between the achiral conjugated pyridine‐based polymer acceptor (PFpy) and the chiral binaphthyl‐based donor (S‐/R‐2Cz). Significantly, the resulting chiral coassembled hosts (S‐/R‐2Cz)0.2‐(PFpy)0.8 greatly promote a commercially available achiral phosphorescence emitter to achieve solution‐processed red CP‐EL device performances at 620 nm with a high external quantum efficiency of 4.1% and a large |gEL| value of 0.014.

π‐Extended End Groups Enable High‐Performance All‐Polymer Solar Cells with Near‐Infrared Absorption

Comprehensive SummaryNarrow‐bandgap n‐type polymers are essential for advancing the development of all‐polymer solar cells (all‐PSCs). Herein, we developed a novel polymer acceptor PNT with π‐extended 2‐(3‐oxo‐2,3‐dihydro‐1H‐cyclopenta[b]naphthalen‐1‐ylidene) malononitrile (CPNM) end groups. Compared to commonly used 2‐(3‐oxo‐2,3‐dihydro‐1H‐cyclopenta[b]naphthalen‐1ylidene) malononitrile (IC) units, CPNM units have a further extended fused ring, providing the PNT polymer with extended absorption into the near‐IR region (903 nm) and exhibiting a narrow optical bandgap (1.37 eV). Furthermore, PNT exhibits a high electron mobility (6.79 × 10−4 cm2·V−1·S−1) and a relatively high‐lying lowest unoccupied molecular orbital (LUMO) energy level of −3.80 eV. When blended with PBDB‐T, all‐PSC achieves a power conversion efficiency (PCE) of 13.7% and a high short‐circuit current density (JSC) of 24.4 mA·cm−2, mainly attributed to broad absorption (600—900 nm) and efficient charge separation and collection. Our study provides a promising polymer acceptor for all‐PSCs and demonstrates that π‐extended CPNM units are important to achieve high‐performance for all‐PSCs.

Improving Photovoltaic Performance of All-Polymer Solar Cells by Adding An Amorphous B←N Embedded Polymer as the Third Component.

Currently, most of the disclosed ternary strategies to improve photovoltaic performance of all-polymer solar cells commonly focus on the guest polymers having similar structures with the host polymer donors or acceptors. Herein, we develop a distinctive ternary method that adding an amorphous B←N embedded polymer named BN-Cl-2fT to a crystallized host polymer blend of PM6 and PY-TT (a copolymer of Y6 and thieno[3,2-b]thiophene). Although the structures between BN-Cl-2fT and PM6 and PY-TT are completely different, excellent miscibility is found between BN-Cl-2fT and both of the host PM6 and PY-TT, which can be interpreted by the crowded phenyl groups anchoring along the backbone of BN-Cl-2fT, leading to weak self-aggregation. GIWAXS measurements explicitly confirm the crystallization of PM6 and PY-TT and amorphous feature of BN-Cl-2fT. Furthermore, adding 10 wt% BN-Cl-2fT to PM6:PY-TT could significantly enhance the crystallization of the host polymers. Thus the ternary devices based on PM6:PY-TT:BN-Cl-2fT afford promoted JSC (23.29versus 21.80mA/cm2 ), FF (62.4%versus 60.0%), and PCE (13.70%versus 12.23%) in contrast to these parameters of binary devices based on PM6:PY-TT. We provide a unique and enlightening avenue to design high performance all-PSCs by adding amorphous B←N embedded polymers as guest component to enhance host-crystallization. This article is protected by copyright. All rights reserved.

Regulating the Sequence Structure of Conjugated Block Copolymers Enables Large-Area Single-Component Organic Solar Cells with High Efficiency and Stability.

Single-component organic solar cells (SCOSCs) based on conjugated block copolymers (CBCs) by covalently bonding a polymer donor and polymer acceptor become more and more appealing due to the formation of a favorable and stable morphology. Unfortunately, a deep understanding of the effect of the assembly behavior caused by the sequence structure of CBCs on the device performance is still missing. Herein, from the aspect of manipulating the sequence length and distribution regularity of CBCs, we synthesized a series of new CBCs, namely D18(20)-b-PYIT, D18(40)-b-PYIT and D18(60)-b-PYIT by two-pot polymerization, and D18(40)-b-PYIT(r) by traditional one-pot method. It is observed that precise manipulation of sequence length and distribution regularity of the polymer blocks fine-tunes the self-assembly of the CBCs, optimizes film morphology, improves optoelectronic properties, and reduces energy loss, leading to simultaneously improved efficiency and stability. Among these CBCs, the D18(40)-b-PYIT-based device achieves a high efficiency of 13.4 % with enhanced stability, which is an outstanding performance among SCOSCs. Importantly, the regular sequence distribution and suitable sequence length of the CBCs enable a facile film-forming process of the printed device. For the first time, the blade-coated large-area rigid/flexible SCOSCs are fabricated, delivering an impressive efficiency of 11.62 %/10.73 %, much higher than their corresponding binary devices.

Regulating the Sequence Structure of Conjugated Block Copolymers Enables Large‐Area Single‐Component Organic Solar Cells with High Efficiency and Stability

AbstractSingle‐component organic solar cells (SCOSCs) based on conjugated block copolymers (CBCs) by covalently bonding a polymer donor and polymer acceptor become more and more appealing due to the formation of a favorable and stable morphology. Unfortunately, a deep understanding of the effect of the assembly behavior caused by the sequence structure of CBCs on the device performance is still missing. Herein, from the aspect of manipulating the sequence length and distribution regularity of CBCs, we synthesized a series of new CBCs, namely D18(20)‐b‐PYIT, D18(40)‐b‐PYIT and D18(60)‐b‐PYIT by two‐pot polymerization, and D18(40)‐b‐PYIT(r) by traditional one‐pot method. It is observed that precise manipulation of sequence length and distribution regularity of the polymer blocks fine‐tunes the self‐assembly of the CBCs, optimizes film morphology, improves optoelectronic properties, and reduces energy loss, leading to simultaneously improved efficiency and stability. Among these CBCs, the D18(40)‐b‐PYIT‐based device achieves a high efficiency of 13.4 % with enhanced stability, which is an outstanding performance among SCOSCs. Importantly, the regular sequence distribution and suitable sequence length of the CBCs enable a facile film‐forming process of the printed device. For the first time, the blade‐coated large‐area rigid/flexible SCOSCs are fabricated, delivering an impressive efficiency of 11.62 %/10.73 %, much higher than their corresponding binary devices.

An asymmetric non-fused electron-deficient building block for low-cost polymer acceptor in all-polymer solar cells

An asymmetric non-fused electron-deficient building block for low-cost polymer acceptor in all-polymer solar cells

Binary all-polymer solar cells with efficiency over 17% by fine-tuning halogenated thiophene linkers of polymer acceptors

All-polymer solar cells (APSCs) have achieved significant advances because of the rising of polymerized small molecular acceptors (PSMAs). While, the effect of halogen atoms on PSMAs in linkers has not been systematically studied. Herein, three PSMAs of PZC1, PZC2, and PZC3 are designed and synthesized by introducing fluorine and chlorine atom on the linkers to fine-tune their optoelectronic and molecular packing properties. Both halogenated polymer acceptors exhibit a slightly blue-shifted absorption range as well as deeper-lying frontier energy levels. When compared with non-halogenated PZC1, the fluorinated polymer acceptor (PZC2) presents better co-planar and rigid molecular conformation. The 3,4-dichlorothiophene-based polymer acceptor (PZC3) displays a distinctly twisted molecular chain between terminal groups and 3,4-dichlorothiophene owing to the steric hindrance between chlorine (Cl) and hydrogen (H) atoms. Due to the optimal morphologies in PM6:PZC2 film, the corresponding devices exhibit an excellent PCE of 17.30%, superior to those of PM6:PZC1 (13.83%) and PM6:PZC3 (15.75%) based devices. The mechanical robustness of three blend films is further investigated. PZC2-based films exhibit outstanding mechanical flexibility. Afterwards, the PM6:PZC2-based flexible devices achieve a PCE of 14.24%. Our results demonstrate that the usage of halogenated thiophene offers a practical way to fine-tune the performance of APSCs.

Biselenophene Imide: Enabling Polymer Acceptor with High Electron Mobility for High-Performance All-Polymer Solar Cells.

The shortage of narrow band gap polymer acceptors with high electron mobility is the major bottleneck for developing efficient all-polymer solar cells (all-PSCs). Herein, we synthesize a distannylated electron-deficient biselenophene imide monomer (BSeI-Tin) with high purity/reactivity, affording an excellent chance to access acceptor-acceptor (A-A) type polymer acceptors. Copolymerizing BSeI-Tin with dibrominated monomer Y5-Br, the resulting A-A polymer PY5-BSeI shows a higher molecular weight, narrower band gap, deeper-lying frontier molecular orbital levels and larger electron mobility than the donor-acceptor type counterpart PY5-BSe. Consequently, the PY5-BSeI-based all-PSCs deliver a remarkable efficiency of 17.77 % with a high short-circuit current of 24.93 mA cm-2 and fill factor of 75.83 %. This efficiency is much higher than that (10.70 %) of the PY5-BSe-based devices. Our study demonstrates that BSeI is a promising building block for constructing high-performance polymer acceptors and stannylation of electron-deficient building blocks offers an excellent approach to developing A-A type polymers for all-PSCs and even beyond.

Biselenophene Imide: Enabling Polymer Acceptor with High Electron Mobility for High‐Performance All‐Polymer Solar Cells

AbstractThe shortage of narrow band gap polymer acceptors with high electron mobility is the major bottleneck for developing efficient all‐polymer solar cells (all‐PSCs). Herein, we synthesize a distannylated electron‐deficient biselenophene imide monomer (BSeI‐Tin) with high purity/reactivity, affording an excellent chance to access acceptor–acceptor (A–A) type polymer acceptors. Copolymerizing BSeI‐Tin with dibrominated monomer Y5‐Br, the resulting A–A polymer PY5‐BSeI shows a higher molecular weight, narrower band gap, deeper‐lying frontier molecular orbital levels and larger electron mobility than the donor–acceptor type counterpart PY5‐BSe. Consequently, the PY5‐BSeI‐based all‐PSCs deliver a remarkable efficiency of 17.77 % with a high short‐circuit current of 24.93 mA cm−2 and fill factor of 75.83 %. This efficiency is much higher than that (10.70 %) of the PY5‐BSe‐based devices. Our study demonstrates that BSeI is a promising building block for constructing high‐performance polymer acceptors and stannylation of electron‐deficient building blocks offers an excellent approach to developing A–A type polymers for all‐PSCs and even beyond.

Anthradithiophene (ADT)-Based Polymerized Non-Fullerene Acceptors for All-Polymer Solar Cells.

Realizing efficient all-polymer solar cell (APSC) acceptors typically involves increased building block synthetic complexity, hence potentially unscalable syntheses and/or prohibitive costs. Here we report the synthesis, characterization, and implementation in APSCs of three new polymer acceptors P1-P3 using a scalable donor fragment, bis(2-octyldodecyl)anthra[1,2-b : 5,6-b']dithiophene-4,10-dicarboxylate (ADT) co-polymerized with the high-efficiency acceptor units, NDI, Y6, and IDIC. All three copolymers have comparable photophysics to known polymers; however, APSCs fabricated by blending P1, P2 and P3 with donor polymers PM5 and PM6 exhibit modest power conversion efficiencies (PCEs), with the champion P2-based APSC achieving PCE=5.64 %. Detailed morphological and microstructural analysis by AFM and GIWAXS reveal a non-optimal APSC active layer morphology, which suppresses charge transport. Despite the modest efficiencies, these APSCs demonstrate the feasibility of using ADT as a scalable and inexpensive electron rich/donor building block for APSCs.

Role of Aromatic Heterocyclic Core-Based Materials as Donors for Organic and as Hole-Transporting Materials for Perovskites Solar cells

Hole-transporting materials (HTMs) have revolutionized the field of photovoltaics for solar cell devices. Herein, novel butterfly-shaped hole transport material (HTM) 2,7-DMPZ (R) containing twisted core unit is used to develop novel molecules (Q1–Q6) by fitting suitable donor groups at peripheral regions of 2,7-DMPZ. To investigate the power conversion efficiency (PCE) of Q1–Q6, different analyses, including optical, frontier molecular orbitals (FMOs), molecular electrostatic potential (MEP), density of states (DOS), transition density of states (TDM), and charge transfer (CT) analysis are employed using various density functional theory (DFT) and time-dependent-DFT (TD-DFT) approaches. Excitation, binding, and reorganization energy along with open-circuit voltage of Q1–Q6 molecules are estimated. The UV–Visible study elucidates that these molecules exhibited redshifts (329–343[Formula: see text]nm) absorption higher and comparable with the R molecule (342[Formula: see text]nm). The HOMO–LUMO gap of Q1–Q6 (5.31–5.38[Formula: see text]eV) is also narrower than R (5.49[Formula: see text]eV), indicating that designed molecules can show higher charge transfer than R, which can ultimately produce higher PCE values. In case of hole reorganization energy, the hole mobilities are found more valuable than R. For charge transfer analysis, the Q6 molecule is complexed with PC[Formula: see text]BM acceptor polymer that shows promising charge transfer between the Q6/PC[Formula: see text]BM complex. All studies illustrate that proposed molecules (Q1–Q6) have a great capacity to further improve the optical and photovoltaic parameters when they will be used in efficient organic (as donors) and perovskite (as HTM) solar cells and can show higher performances than R. Therefore, these newly designed molecules (Q1–Q6) rerecommended to the experimentalists for the synthesis to be employed as donors in organic and as HTMs in perovskite solar cells applications.

Chemically Recyclable Conjugated Polymer and One‐Shot Preparation of Thermally Stable and Efficient Bulk‐Heterojunction from Recycled Monomer

AbstractRecyclable conjugated polymers are important for realizing eco‐friendly electronics with advantages of solution processability and flexibility. A recyclable conjugated polymer, PY‐TIP is developed, of which a key monomer is successfully extracted via a mild depolymerization process and is reused for the synthesis of novel conjugated polymers. One‐shot preparation of polymer acceptor and its bulk‐heterojunction (BHJ) is demonstrated from the recycled monomer, Y5‐TA, for the first time and the resulting BHJ film shows optimal nanoscale morphology for efficient charge generation and transport. As a result, the solar cells prepared using the BHJ film show a higher efficiency of 13.08% and much improved thermal and mechanical stability compared with those based on the small molecular acceptor. These results are important in that the various polymers can be prepared from the recycled monomer in a solid state without organic solvents and purification step and this strategy is effective for improving the thermal and mechanical stability of the BHJ film as well as achieving high photovoltaic performance. PY‐TIP is exemplary in that it can reproduce its monomer which can be used to synthesize conjugated polymers with novel chemical structures and physical properties. This work provides a design guideline for developing recyclable conjugated polymers with dynamic covalent bonds.

Charge Concentration Limits the Hydrogen Evolution Rate in Organic Nanoparticle Photocatalysts.

Time-resolved microwave conductivity is used to compare aqueous-soluble organic nanoparticle photocatalysts and bulk thin films composed of the same mixture of semiconducting polymer and non-fullerene acceptor molecule and the relationship between composition, interfacial surface area, charge-carrier dynamics, and photocatalytic activity is examined. The rate of hydrogen evolution reaction by nanoparticles composed of various donor:acceptor blend ratio compositions is quantitatively measured, and it is found that the most active blend ratio displays a hydrogen quantum yield of 0.83% per photon. Moreover, it is found that nanoparticle photocatalytic activity corresponds directly to charge generation, and that nanoparticles have 3× more long-lived accumulated charges relative to bulk samples of the same material composition. These results suggest that, under the current reaction conditions, with ≈3× solar flux, catalytic activity by the nanoparticles is limited by the concentration of electrons and holes in operando and not a finite number of active surface sites or the catalytic rate at the interface. This provides a clear design goal for the next generation of efficient photocatalytic nanoparticles.

Polythiophene Derivatives for Efficient All‐Polymer Solar Cells

AbstractPolymerized small molecule acceptors have recently greatly facilitated the development of all‐polymer solar cells (All‐PSCs) with respect to the power conversion efficiencies (PCEs). However, high‐performance and low‐cost polymer donors for All‐PSCs are still lacking, limiting further large‐scale manufacturing of All‐PSCs. Herein, this work designs and synthesizes a new thiophene derivative, FETVT, featuring vinyl‐bridged fluorine and ester‐substituted monothiophene. Incorporation of FETVT into a polymer yields a high‐performance polythiophene derivative PFETVT‐T, which exhibits deep‐lying HOMO level, suitable solution pre‐aggregation ability, finely‐tuned polymer crystallinity, and appropriate thermodynamic miscibility with the polymer acceptor L15. As a result, binary based on PFETVT‐T achieves a record PCE of 11.81% with agood stability, representing a breakthrough for polythiophenes and their derivatives‐based All‐PSCs, which is also significantly higher than that (1.92%) of All‐PSCs based on its isomerized analog. Remarkably, PFETVT‐T achieves an impressive PCE exceeding 16% via the implementation of a ternary blend design. These findings offer a hopeful pathway toward attaining high‐performance, stable, and cost‐effective PSCs.

Atomistic Structural Engineering of Conjugated Microporous Polymers Promotes Photocatalytic Biomass Valorization

AbstractPolymer photocatalysts have great promise for solar fuel production due to their flexible structural and functional designability. However, their photocatalytic efficiencies are still unsatisfactory, limited by their intrinsically large exciton binding energy and fast charge recombination. Herein, the atomistic structural engineering of donor–acceptor (D−A) polymer photocatalysts for enhanced charge separation and photocatalytic hydrogen production is proposed. By changing the electron affinity of the acceptor units, the electron delocalization and exciton binding energy of the polymeric networks can be readily tuned, resulting in enhanced charge separation efficiency and photocatalytic activity. The optimal sample shows the highest H2 production rate of 3207 µmol g−1 h−1 in the presence of ascorbic acid as the sacrificial agent. Moreover, the photocatalytic H2 production can be coupled with almost stoichiometrical conversion of 5‐hydroxymethyl furfural to 2,5‐diformylfuran.

Templated 2D Polymer Heterojunctions for Improved Photocatalytic Hydrogen Production.

2D polymers have emerged as one of the most promising classes of organic photocatalysts for solar fuel production due to their tunability, charge-transport properties, and robustness. They arehoweverdifficult to process and so there are limited studies into the formation of heterojunction materials incorporating these components. In this work, a novel templating approach is used to combine an imine-based donor polymer and an acceptor polymer formed through Knoevenagel condensation. Heterojunction formation is shown to be highly dependent on the topological match of the donor and acceptor polymers with the most active templated material found to be between three and nine times more active for photocatalysis than its constituent components. Transient absorption spectroscopy reveals that this improvement is due to faster charge separation and more efficient charge extraction in the templated heterojunction. The templated material shows a very high hydrogen evolution rate of >20mmol h-1 m-2 with an ascorbic acid hole scavenger but also produces hydrogen in the presence of only water and a cobalt-based redox mediator. This suggeststhe improved charge-separation interface and reduced trapping accessed through this approach could be suitable for Z-scheme formation.