Polymer Donor Research Articles

Polymerized-Small-Molecule Acceptors Featuring Siloxane-Terminated Side Chains for Mechanically Robust All-Polymer Solar Cells.

Flexible and stretchable organic solar cells (OSCs) show great promise in wearable and stretchable electronic applications. However, current high-performance OSCs consisting of polymer donors (PDs) and small-molecule acceptors (SMAs) face significant challenges in achieving both high power conversion efficiency (PCE) and excellent stretch-ability. In this study, we synthesized a new polymerized-small-molecule acceptor (P-SMA) PY-SiO featuring siloxane-terminated side chains and compared its photovoltaic and mechanical performance to that of the reference PY-EH with ethylhexyl-terminated side chains. We found that the incorporation of siloxane-terminated side chains in PY-SiO enhanced the molecular aggregation and charge transport, leading to an optimized film morphology. The resultant of all-polymer solar cells (all-PSCs) based on PBDB-T/PY-SiO showed a higher PCE of 12.04% than the PY-EH-based one (10.85%). Furthermore, the siloxane-terminated side chains also increased the interchain distance and provided a larger free volume for chain rotation and reconfiguration, resulting in a higher film crack-onset strain (COS: 18.32% for PBDB-T/PY-SiO vs 11.15% for PBDB-T/PY-EH). Additionally, the PY-SiO-based stretchable all-PSCs exhibited an impressive PCE of 9.8% and retained >70% of its original PCE even under a substantial 20% strain, exceeding the performance of the PY-EH-based stretchable all-PSCs. Our result suggests the great potential of the siloxane-terminated side chain for achieving high-performance and stretchable OSCs.

Design Principles of Diketopyrrolopyrrole‐Thienopyrrolodione Acceptor1–Acceptor2 Copolymers

AbstractThe design principles of acceptor1–acceptor2 copolymers featuring alternating diketopyrrolopyrrole (DPP) and thienopyrrolodione (TPD) moieties are investigated. The investigated series of polymers is obtained by varying the aromatic linker between the two acceptor motifs between thiophene, thiazole, pyridine, and benzene. High electron affinities between 3.96 and 4.42 eV, facilitated by the synergy of the acceptor motifs are determined with optical gaps between 1.37 and 2.02 eV. Grazing incidence wide‐angle X‐ray scattering studies reveal a range of film morphologies after thermal annealing, including face‐on, end‐on and superstructure edge‐on‐like crystallites. Conversely, all materials form thin edge‐on layers on the polymer–air interface, as demonstrated by multi‐elemental near‐edge X‐ray absorption fine‐structure spectroscopy. The benefit of the electron‐deficient linkers thiazole and pyridine is evident: In organic field effect transistors, electron mobilities of up to 4.6 × 10−2 cm2 V−1 s−1 are obtained with outstanding on/off current ratios of 5 × 105, facilitated by the absence of detectable hole transport in these materials. Viability for all‐polymer solar cells is assessed in active layer blends with the donor polymer PM6, yielding a maximum average power conversion efficiency of 4.8% and an open circuit voltage above 1 V.

Wide-bandgap donor polymers from organic photovoltaics as dopant-free hole transport layers for perovskite solar cells

Dopant-free polymer hole transport materials (HTMs) exhibit high thermal stability, hydrophobicity and film-processing capabilities, demonstrating excellent device efficiency and stability in perovskite solar cells (PSCs). Continued innovation of wide-bandgap polymers in organic photovoltaics (OPV) provides a valuable toolbox for developing polymeric HTMs. Here, we propose an effective molecule design for selecting structurally relevant polymers (D18, D18-Cl, PBQx-TCl) available for commercialization. We discover that the highly planar conjugated backbones play a crucial role in regulating the packing orientation of the film relative to the perovskite. The moderate aggregation with face-on packing orientation is conducive to the high-quality film, which is responsible for better contact with perovskite and superior charge extraction and transport. Simultaneously, these polymers with robust passivation enhanced the open circuit voltage (VOC) without additional passivation layers, streamlining the device process. Consequently, a PSC using dopant-free PBQx-TCl HTL demonstrated an efficiency of 24.12 % with a high VOC of 1.20 V and good operational stability (T90 > 600 h). This work reveals transparent structure–function-performance relationships between molecules and devices, paving the way for the subsequent development of high-performance HTMs.

19% efficiency in organic solar cells of Benzo[1,2-b:4,5-b′]Difuran-based donor polymer realized by volatile + non-volatile dual-solid-additive strategy

Though the application-promising photovoltaic technology named organic solar cells (OSCs) have been close to 20% benchmark power conversion efficiency (PCE) within fabrication friendly single-junction devices, these achievements are enabled by polymer donors based on benzodithiophene cores, requiring toxic production steps. Whilst, the bio-renewable benzo[1,2-b:4,5-b′]difuran unit constructed polymer donors cannot yield comparable efficiency, though their lower steric hindrance is widely appreciated. OSC field has paid great attention on optimizing their performance by chemistry design, yet the device engineering is relatively neglected compared to what have been done on the benzodithiophene side. Here we report a new dual additive strategy of simultaneously applying volatile (2-CN) and non-volatile (MF) solid additives to reduce non-radiative voltage loss and boost charge generation, via an occupying evaporated left vacancies in polymer matrix process. Consequently, the target system D18-Fu:L8-BO’s efficiency is promoted to 19.11%, representing the cutting-edge level of this research topic.

Recent Advances of Imide‐Functionalized Polymer Donors for Non‐fullerene Solar Cells†

Comprehensive SummaryIn recent years, there has been a shift towards using non‐fullerene electron acceptors in organic solar cells (OSCs) as a replacement for fullerene derivatives. This change requires polymer donors that possess compatible physical properties, such as absorption range, HOMO energy level, miscibility, and crystallinity. Moreover, the high cost and poor batch‐to‐batch reproducibility of polymer donors also hinder future large‐scale manufacturing. These emphasize the need to explore alternative types of polymer donors. The imide‐functionalized building units possess several key attributes that make their polymers highly promising for non‐fullerene OSCs. These attributes include ease of synthesis, strong electron‐withdrawing ability, rigid and co‐planar structure, and the ability to easily tune solubility through imide side chains. In this review, we summarized the synthetic routes of imide building units, and the structural evolution of imide‐functionalized polymer donors by focusing on the effects of polymer structure on their physical, optoelectronic, and photovoltaic properties. We hope that this mini‐review will serve as a catalyst for future research on imide‐functionalized polymers toward high‐performance, cost‐effective, and durable organic solar cells (OSCs).

Selecting Solid Additives to Control the Interaction between Polymer Donors and Additives for Constructing High-Efficiency Organic Solar Cells

Selecting Solid Additives to Control the Interaction between Polymer Donors and Additives for Constructing High-Efficiency Organic Solar Cells

Hydrogen‐Bonding Interactions Between Terpolymers Enable Excellent Device Efficiency and Operational Stability of Non‐Halogenated Solvent‐Processed Polymer Solar Cells

AbstractAlthough polymer solar cells (PSCs) have shown considerable power conversion efficiency (PCE) potential, their poor operational stability is a major obstacle for their future commercialization. In this study, the ternary‐blend strategy based on D1–A–D1–D2‐type conjugated random terpolymers containing hydrogen–bonding sites is employed to simultaneously improve device efficiency and long‐term stability. Notably, the PM6‐ThEG:PM6‐ThOH:Y6‐BO ternary‐blend system exhibits a remarkable PCE of 17.2% with superior photo, thermal, and mechanical stability, outperforming those of binary devices based on PM6, PM6‐ThEG, and PM6‐ThOH polymer donors. These outstanding results are likely attributed to the robust molecular lock via hydrogen bonds between PM6‐ThEG and PM6‐ThOH terpolymers, which can induce strong intermolecular packing, a dense 3D terpolymer network, and optimized morphology. These results also correlate well with the computational study. A comprehensive analysis of optoelectronic and morphological properties as well as the exploration of underlying physical mechanisms collectively verifies the effectiveness of this approach based on mixed random terpolymers with hydrogen‐bonding moiety to achieve the non‐halogenated solvent‐processed PSCs with exceptional efficiency and operational stability.

High Open-Circuit Voltage Organic Solar Cells with 19.2% Efficiency Enabled by Synergistic Side-Chain Engineering.

Restricted by the energy-gap law, state-of-the-art organic solar cells (OSCs) exhibit relatively low open-circuit voltage (VOC) because of large nonradiative energy losses (ΔEnonrad). Moreover, the trade-off between VOC and external quantum efficiency (EQE) of OSCs is more distinctive; the power conversion efficiencies (PCEs) of OSCs are still <15% with VOCs of >1.0V. Herein, the electronic properties and aggregation behaviors of non-fullerene acceptors (NFAs) are carefully considered and then a new NFA (Z19) is delicately designed by simultaneously introducing alkoxy and phenyl-substituted alkyl chains to the conjugated backbone. Z19 exhibits a hypochromatic-shifted absorption spectrum, high-lying lowest unoccupied molecular orbital energy level and ordered 2D packing mode. The D18:Z19-based blend film exhibits favorable phase separation with face-on dominated molecular orientation, facilitating charge transport properties. Consequently, D18:Z19 binary devices afford an exciting PCE of 19.2% with a high VOC of 1.002V, surpassing Y6-2O-based devices. The former is the highest PCE reported to date for OSCs with VOCs of >1.0V. Moreover, theΔEnonrad of Z19- (0.200eV) and Y6-2O-based (0.155eV) devices are lower than that of Y6-based (0.239eV) devices. Indications are that the design of such NFA, considering the energy-gap law, could promote a new breakthrough in OSCs.

Synchronous Regulation of Donor and Acceptor Microstructure using Thiophene‐Derived Non‐Halogenated Solvent Additives for Efficient and Stable Organic Solar Cells

AbstractSolvent additives are pivotal for enhancing the morphology, efficiency, and stability of organic solar cells (OSCs). However, the widely used additive, 1,8‐diiodooctane (DIO), has drawbacks like harmful halogen content and potential OSC degradation. To address these issues, novel non‐halogenated, thienyl‐alkyl‐thienyl structural solvent additives—DTP, DTH, and DTN—featuring varying alkyl linker lengths of (CH2)3, (CH2)6, and (CH2)9, respectively are introduced. Additives with longer alkyl linkers, DTH and DTN, effectively dissolve and strongly interact with both the donor polymer PM6 and acceptor L8‐BO. This dual interaction enables precise tuning of their microstructures, resulting in enhanced crystallinity. Upon incorporating DTH as an additive in OSCs (PM6:L8‐BO), a minimal voltage loss is observed, leading to an impressive efficiency of 18.51%, surpassing the 17.90% achieved with DIO. Furthermore, DTH‐based devices demonstrated superior photostability. In a ternary blend system (PM6:D18‐Cl:L8‐BO), an efficiency of 19.07% is attained, outperforming previous non‐halogenated solvent additive‐based OSCs. Furthermore, employing a non‐halogenated processing solvent combination of toluene and carbon disulfide, a high PCE of 18.82% is achieved. These results underscore the efficacy of designing solvent additives with aromatic and alkyl units, enabling tailored interactions with the donor and acceptor, thereby presenting a robust strategy for optimizing OSC performance and stability.

Polymerizing M-Series Acceptors for Efficient Polymer Solar Cells: Effect of the Molecular Shape.

Currently, high-performance polymerized small-molecule acceptors (PSMAs) based on ADA-type SMAs are still rare and greatly demanded for polymer solar cells (PSCs). Herein, two novel regioregular PSMAs (PW-Se and PS-Se) are designed and synthesized by using centrosymmetric (linear-shaped) and axisymmetric (banana-shaped) ADA-type SMAs as the main building blocks, respectively. It is demonstrated that photovoltaic performance of the PSMAs can be significantly improved by optimizing the configuration of ADA-type SMAs. Compared to the axisymmetric SMA-based polymer (PS-Se), PW-Se using a centrosymmetric SMA as the main building block exhibits better backbone coplanarity thereby resulting in bathochromically shifted absorption with a higher absorption coefficient, tighter interchain π-π stacking, and more favorable blend film morphology. As a result, enhanced and more-balanced charge transport, better exciton dissociation, and reduced charge recombination are achieved for PW-Se-based devices with PM6 as polymer donor. Benefiting from these positive factors, the optimal PM6:PW-Se-based device exhibits a higher power conversion efficiency (PCE) of 15.65% compared to the PM6:PS-Se-based device (8.90%). Furthermore, incorporation of PW-Se as a third component in the binary active layer of PM6:M36 yields ternary devices with an outstanding PCE of 18.0%, which is the highest value for PSCs based on ADA-type SMAs, to the best of the knowledge.

Design of a Low‐Cost Electron Acceptor for Highly Efficient Organic Solar Cell through Alkyl Chain Branching Position Manipulation

The state‐of‐the‐art bulk‐heterojunction (BHJ) organic solar cells (OSCs) typically include expensive fused‐ring electron acceptors, hindering industrialization. Designing low‐cost and highly efficient electron acceptors remains challenging. Herein, two low‐cost electron acceptors (DTB2 and DTB3) based on a conjugated 1,4‐di(thiophen‐2‐yl)benzene (DTB) core and two fluorinated 2‐(3‐oxo‐2,3‐dihydroinden‐1‐ylidene)malononitrile end‐groups are reported. Their only difference is the alkyl chain branching position on the benzene ring. Both acceptors exhibit similar low optical gaps of ≈1.35 eV but different molecular orientations. DTB2 shows an edge‐on arrangement, while DTB3, with a shift in branching positions toward the conjugated backbone, produces a face‐on arrangement. Such molecular orientations are maintained in their BHJ layers after blending with a polymer donor PBQx‐TF. The PBQx‐TF:DTB3 film demonstrates superior BHJ phase‐separation and faster charge carrier generation (0.44 ps) than those of the PBQx‐TF:DTB2 film (50 ps). As a result, the DTB2‐based OSC achieves a modest power conversion efficiency (PCE) of 8.5%. While the DTB3‐based OSC produces an outstanding PCE of 15.3%, which is much higher than those of the reported DTB‐based OSCs. Besides, DTB3 has a figure of merit up to 0.46, higher than the state‐of‐the‐art fused‐ring electron acceptors. This work provides new insights into designing low‐cost and highly efficient electron acceptors.

Correlation between materials and band‐selective detection in organic photodetectors based on bulk heterojunction

AbstractFor wavelength‐selective photodetection or color discrimination, organic photodetectors (OPDs) can provide significant advantages as solution processability, chemical versatility and functionality. To eliminate the need for commonly used filters, the development of a narrowing approach that simultaneously achieves a selective detection range of less than 50 nm bandwidth and a spectral response of ~20% as efficiency at a required wavelength, remains a real challenge. Herein, different donor polymers and small acceptor molecules have been involved in bulk heterojunctions (BHJs) at 1:1 weight ratio as photoactive layers in specific OPDs. Indeed, the mechanism of charge collection in these OPDs is based on the charge collection narrowing (CCN) principle. In this approach, the detection window can be selected to match the absorption onset of the junction materials used in the BHJ layer. Although essentially based on very thick layers, we are focusing here on OPDs with layer thicknesses of less than 2 μm and post‐deposition annealing temperatures not in excess of 100°C.

Cost-effective polymer donors based on pyridine for efficient nonfullerene polymer solar cells

Developing cost-effective polymer donors that can match nonfullerene acceptors is very important for practical applications of polymer solar cells (PSCs). In this work, low-cost 3-fluoropyridine and pyridine were employed as acceptor unit cores to construct cost-effective polymers PBDT-FPy, PBDT-Py and PBDF-Py by copolymerizing with commercially available donor units. PBDT-FPy, PBDT-Py and PBDF-Py show wide-bandgap of 2.08, 2.15 and 2.05 eV, respectively. Due to the strong electronegativity of nitrogen atom in pyridine and Nδ− … Hδ+ noncovalent dipole-dipole interactions, all polymers exhibit deep-lying highest-occupied molecular orbital (HOMO) energy levels, strong intermolecular π-π interaction and good planarity. The PBDT-FPy: Y6 based device exhibits a power conversion efficiency (PCE) of 8.34%, while the performance of PBDT-Py: Y6 and PBDF-Py: Y6 devices was significantly improved, with PCE of 10.02% and 10.00%. The results indicate that pyridine with simple structure and low synthetic cost is a promising building block to construct high-performance cost-effective polymer donors for application in PSCs.

Design and Synthesis of Dibenzothiadiazolopyrrolothiophene (DBTPT)‐Based Acceptors for Efficient Organic Photovoltaic Cells

AbstractThe central core in non‐fullerene acceptors (NFAs) plays a crucial role in determining the efficiency of organic photovoltaic (OPV) cells. To further advance the development of OPV cells, it is crucial to synthesize novel central cores for constructing high‐performance NFAs. Here, dibenzothiadiazolopyrrolothiophene (DBTPT) is introduced, a ladder‐type [1,2,5]thiadiazolo[3,4‐e]indole‐fused pentacyclic thiophene unit, into photovoltaic materials. By employing the DBTPT unit as the rigid molecular backbone and modifying the side chain of the thiophene π‐bridge, two new acceptor‐π‐acceptor’‐donor‐acceptor’‐π‐acceptor (A‐π‐A'DA’‐π‐A)‐type acceptors (T6 and T9) are synthesized. The effects of lateral alkyl and alkoxy side chains on the optoelectronic properties, charge transport, and molecular packing order are systematically investigated. When blended with polymer donor Poly[(2,6‐(4,8‐bis(5‐(2‐ethylhexyl)thiophen‐2‐yl)‐benzo[1,2‐b:4,5‐b']dithiophene))‐alt‐(5,5‐(1',3'‐di‐2‐thienyl‐5'7'‐bis(2‐ethylhexyl)benzo[1',2'‐c:4',5'‐c']dithiophene‐4,8‐dione))] (PBDB‐T), the blend film based on T9 with alkoxy side chains shows favorable molecular stacking and phase separation, resulting in excellent charge transfer performance. Benefiting low energetic disorder, PBDB‐T:T9‐based cell achieves an efficiency of 12.6% with a markedly low energy loss of 0.568 eV. The preliminary results demonstrate that the DBTPT unit has great potential for the construction of novel NFAs for high‐performance OPV cells.

Synergistic Regulation of Crystallization Kinetics of Donor/Acceptor by New Volatile Additives for High Performance Organic Solar Cells

AbstractIdeal nanoscale morphology of heterojunction active layer is important for the development of organic solar cells (OSCs). However, the mismatched crystalline kinetic between the polymer donor and small molecular acceptor often leads to the difficulties in controlling the morphology of the active layer. Herein, polar 1,2‐dibromo‐4,5‐difluorobenzene (DFB) and non‐polar 1,4‐dibromotetrafluorobenzene (TFB) are developed as the volatile additives for OSCs. More attractively, different from the reported volatile additives, both new volatile additives can simultaneously interact with donor and acceptor, synergistic regulating the crystallization kinetic and well‐balancing the crystallization behaviors between the polymer donor and small molecular acceptor during film formation process. Notably, due to the stronger dipole‐dipole interactions with active layer, polar DFB induces the more favorable film morphology than non‐polar TFB. As a result, the two additives‐treated PM6:Y6 devices both outperform the CN‐treated device (16.13%), and the polar DFB‐treated device deliver a higher efficiency of 17.15% than non‐polar TFB‐treated one (16.30%). With polar DFB additive, PM6:L8‐BO and PM6: BTP‐eC9 also achieve superior efficiency of 18.46% and 18.17%, respectively. This work deepens the insights of regulating crystallization kinetics and optimizing nanoscale morphology by developing simple volatile additives for further achieving high‐efficient OSCs.

Electrostatic Potential Design of Solid Additives for Enhanced Molecular Order of Polymer Donor in Efficient Organic Solar Cells.

Polymeric semiconducting materials struggle to achieve fast charge mobility due to low structural order. In this work, five 1H-indene-1,3(2H)dione-benzene structured halogenated solid additives namely INB-5F, INB-3F, INB-1F, INB-1Cl, and INB-1Br with gradually varied electrostatic potential are designed and utilized to regulate the structural order of polymer donor PM6. Molecular dynamics simulations demonstrate that although the dione unit of these additives tends to adsorb on the backbone of PM6, the reduced electrostatic potential of the halogen-substituted benzene can shift the benzene interacting site from alkyl side chains to the conjugated backbone of PM6, not only leading to enhanced π-π stacking in out-of-plane but also arising new π-π stacking in in-plane together with the appearance of multiple backbone stacking in out-of-plane, consequent to the co-existence of face-on and edge-on molecular orientations. This molecular packing transformation further translates to enhanced charge transport and suppressed carrier recombination in their photovoltaics, with a maximum power conversion efficiency of 19.4% received in PM6/L8-BO layer-by-layer deposited organic solar cells.

Facile Synthesis of Dithienobenzothiadiazoles and D18-Cl Polymer via Na2S-Mediated Rapid Thiophene-Annulations for Organic Solar Cells.

We present a novel synthetic route for the rapid construction of dithieno[3',2':3,4;2'',3'':5,6]benzo[1,2-c][1,2,5]thiadiazoles via Na2S-promoted thiophene annulation. This method facilitated the synthesis of D18-Cl polymer, known for its efficacy as a polymer donor in bulk-heterojunction polymer solar cells. Starting from commercially available 4,7-dihalo-5,6-difluorobenzo[c][1,2,5]thiadiazole, various 4,7-dialkynylated compounds were obtained through Sonogashira reaction conditions. Subsequent Na2S-promoted thiophene annulations yielded DTBT and its derivatives in excellent yields within 10 minutes. DTBT was then utilized as a precursor for the concise synthesis of D18-Cl, benefiting from reduced synthetic steps, mild reaction conditions, decreased complexity, and high overall yields. In another route, a space group-bridged DTBT was directly constructed via Na2S-promoted thiophene annulations and converted into D18-Cl through a couple of steps. This developed protocol offers a straightforward and reliable synthetic tool, conducive to reducing complexities in the production of DTBT-based organic electronic materials, thereby advancing the potential commercialization of organic solar cells.

Dimeric Giant Molecule Acceptors Featuring N‐type Linker: Enhancing Intramolecular Coupling for High‐Performance Polymer Solar Cells

AbstractGiant molecular acceptors (GMAs) are typically designed through the conjugated linking of individual small molecule acceptors (SMAs). This design imparts an extended molecular size, elevating the glass transition temperature (Tg) relative to their SMA counterparts. Consequently, it effectively suppresses the thermodynamic relaxation of the acceptor component when blended with polymer donors to construct stable polymer solar cells (PSCs). Despite their merits, the optimization of their chemical structure for further enhancing of device performance remains challenge. Different from previous reports utilizing p‐type linkers, here, we explore an n‐type linker, specifically the benzothiadiazole unit, to dimerize the SMA units via a click‐like Knoevenagel condensation, affording BT‐DL. In comparison with B‐DL with a benzene linkage, BT‐DL exhibits significantly stronger intramolecular super‐exchange coupling, a desirable property for the acceptor component. Furthermore, BT‐DL demonstrates a higher film absorption coefficient, redshifted absorption, larger crystalline coherence, and higher electron mobility. These inherent advantages of BT‐DL translate into a higher power conversion efficiency of 18.49 % in PSCs, a substantial improvement over the 9.17 % efficiency observed in corresponding devices with B‐DL as the acceptor. Notably, the BT‐DL based device exhibits exceptional stability, retaining over 90 % of its initial efficiency even after enduring 1000 hours of thermal stress at 90 °C. This work provides a cost‐effective approach to the synthesis of n‐type linker‐dimerized GMAs, and highlight their potential advantage in enhancing intramolecular coupling for more efficient and durable photovoltaic technologies.

Dimeric Giant Molecule Acceptors Featuring N-type Linker: Enhancing Intramolecular Coupling for High-Performance Polymer Solar Cells.

Giant molecular acceptors (GMAs) are typically designed through the conjugated linking of individual small molecule acceptors (SMAs). This design imparts an extended molecular size, elevating the glass transition temperature (Tg) relative to their SMA counterparts. Consequently, it effectively suppresses the thermodynamic relaxation of the acceptor component when blended with polymer donors to construct stable polymer solar cells (PSCs). Despite their merits, the optimization of their chemical structure for further enhancing of device performance remains challenge. Different from previous reports utilizing p-type linkers, here, we explore an n-type linker, specifically the benzothiadiazole unit, to dimerize the SMA units via a click-like Knoevenagel condensation, affording BT-DL. In comparison with B-DL with a benzene linkage, BT-DL exhibits significantly stronger intramolecular super-exchange coupling, a desirable property for the acceptor component. Furthermore, BT-DL demonstrates a higher film absorption coefficient, redshifted absorption, larger crystalline coherence, and higher electron mobility. These inherent advantages of BT-DL translate into a higher power conversion efficiency of 18.49 % in PSCs, a substantial improvement over the 9.17 % efficiency observed in corresponding devices with B-DL as the acceptor. Notably, the BT-DL based device exhibits exceptional stability, retaining over 90 % of its initial efficiency even after enduring 1000 hours of thermal stress at 90 °C. This work provides a cost-effective approach to the synthesis of n-type linker-dimerized GMAs, and highlight their potential advantage in enhancing intramolecular coupling for more efficient and durable photovoltaic technologies.

Terpolymer Containing a meta-Octyloxy-phenyl-Modified Dithieno[3,2-f:2',3'-h]quinoxaline Unit Enabling Efficient Organic Solar Cells.

With the rapid development of small-molecule electron acceptors, polymer electron donors are becoming more important than ever in organic photovoltaics, and there is still room for the currently available high-performance polymer donors. To further develop polymer donors with finely tunable structures to achieve better photovoltaic performances, random ternary copolymerization is a useful technique. Herein, by incorporating a new electron-withdrawing segment 2,3-bis(3-octyloxyphenyl)dithieno[3,2-f:2',3'-h]quinoxaline derivative (C12T-TQ) to PM6, a series of terpolymers were synthesized. It is worth noting that the introduction of the C12T-TQ unit can deepen the highest occupied molecular orbital energy levels of the resultant polymers. In addition, the polymer Z6 with a 10% C12T-TQ ratio possesses the highest film absorption coefficient (9.86 × 104 cm-1) among the four polymers. When blended with Y6, it exhibited superior miscibility and mutual crystallinity enhancement between Z6 and Y6, suppressed recombination, better exciton separation and charge collection characteristics, and faster hole transfer in the D-A interface. Consequently, the device of Z6:Y6 successfully achieved enhanced photovoltaic parameters and yielded an efficiency of 17.01%, higher than the 16.18% of the PM6:Y6 device, demonstrating the effectiveness of the meta-octyloxy-phenyl-modified dithieno[3,2-f:2',3'-h]quinoxaline moiety to build promising terpolymer donors for high-performance organic solar cells.