Unraveling the Structure-Property-Performance Relationships of Fused-Ring Nonfullerene Acceptors: Toward a C-Shaped ortho-Benzodipyrrole-Based Acceptor for Highly Efficient Organic Photovoltaics.

The high-performance Y6-based nonfullerene acceptors (NFAs) feature a C-shaped A-DA'D-A-type molecular architecture with a central electron-deficient thiadiazole (Tz) A' unit. In this work, we designed and synthesized a new A-D-A-type NFA, termed CB16, having a C-shaped ortho-benzodipyrrole-based skeleton of Y6 but with the Tz unit eliminated. When processed with nonhalogenated xylene without using any additives, the binary PM6:CB16 devices display a remarkable power conversion efficiency (PCE) of 18.32% with a high open-circuit voltage (Voc) of 0.92 V, surpassing the performance of the corresponding Y6-based devices. In contrast, similarly synthesized SB16, featuring an S-shaped para-benzodipyrrole-based skeleton, yields a low PCE of 0.15% due to the strong side-chain aggregation of SB16. The C-shaped A-DNBND-A skeleton in CB16 and the Y6-series NFAs constitutes the essential structural foundation for achieving exceptional device performance. The central Tz moiety or other A' units can be employed to finely adjust intermolecular interactions. The single-crystal X-ray structure reveals that ortho-benzodipyrrole-embedded A-DNBND-A plays an important role in the formation of a 3D elliptical network packing for efficient charge transport. Solution structures of the PM6:NFAs detected by small- and wide-angle X-ray scattering (SWAXS) indicate that removing the Tz unit in the C-shaped skeleton could reduce the self-packing of CB16, thereby enhancing the complexing and networking with PM6 in the spin-coating solution and the subsequent device film. Elucidating the structure-property-performance relationships of A-DA'D-A-type NFAs in this work paves the way for the future development of structurally simplified A-D-A-type NFAs.

Intrinsically Stretchable Organic Thermoelectric Polymers Enabled by Incorporating Fused-Ring Conjugated Breakers.

While research on organic thermoelectric polymers is making significant progress in recent years, realization of a single polymer material possessing both thermoelectric properties and stretchability for the next generation of self-powered wearable electronics is a challenging task and remains an area yet to be explored. A new molecular engineering concept of "conjugated breaker" is employed to impart stretchability to a highly crystalline diketopyrrolepyrrole (DPP)-based polymer. A hexacyclic diindenothieno[2,3-b]thiophene (DITT) unit, with two 4-octyloxyphenyl groups substituted at the tetrahedral sp3-carbon bridges, is selected to function as the conjugated breaker that can sterically hinder intermolecular packing to reduce polymers' crystallinity. A series of donor-acceptor random copolymers is thus developed via polymerizing the crystalline DPP units with the DITT conjugated breakers. By controlling the monomeric DPP/DITT ratios, DITT30 reaches the optimal balance of crystalline/amorphous regions, exhibiting an exceptional power factor (PF) value up to 12.5 µW m-1 K-2 after FeCl3-doping; while, simultaneously displaying the capability to withstand strains exceeding 100%. More significantly, the doped DITT30 film possesses excellent mechanical endurance, retaining 80% of its initial PF value after 200 cycles of stretching/releasing at a strain of 50%. This research marks a pioneering achievement in creating intrinsically stretchable polymers with exceptional thermoelectric properties.

s-Indacene Revisited: Modular Synthesis and Modulation of Structures and Molecular Orbitals of Hexaaryl Derivatives.

Though s-indacene is an intriguing antiaromatic hydrocarbon of 12 π-electrons, it has been underrepresented due to the lack of efficient and versatile methods to prepare stable derivatives. Herein we report a concise and modular synthetic method for hexaaryl-s-indacene derivatives bearing electron-donating/-accepting groups at specific positions to furnish C2h-, D2h-, and C2v-symmetric substitution patterns. We also report the effects of substituents on their molecular structures, frontier molecular orbital (MO) levels, and magnetically induced ring current tropicities. Both theoretical calculations and X-ray structure analyses indicate that the derivatives of the C2h-substitution pattern adopt different C2h structures with significant bond length alternation depending on the electronic property of the substituents. Due to the nonuniform distribution of the frontier MOs, their energy levels are selectively modulated by the electron-donating substituents. This leads to the inversion of the HOMO and HOMO-1 sequences with respect to those of the intrinsic s-indacene as theoretically predicted and experimentally proven by the absorption spectra at visible and near-infrared regions. The NICS values and the 1H NMR chemical shifts of the s-indacene derivatives indicate their weak antiaromaticity. The different tropicities are explained by the modulation of the HOMO and HOMO-1 levels. In addition, for the hexaxylyl derivative, weak fluorescence from the S2 excited state was detected due to the large energy gap between the S1 and S2 states. Notably, an organic field-effect transistor (OFET) fabricated using the hexaxylyl derivative exhibited moderate hole carrier mobility, a result which opens the door for optoelectronic applications of s-indacene derivatives.

Synthesis and Isomeric Effects of Ladder-Type Alkylated Terbenzodithiophene Derivatives.

A new class of heptacyclic ladder-type terbenzodithiophene (TBDT) structures merging three fused benzodithophenes was developed. Two TBDT conjugated isomers, named as syn-TBDT and anti-TBDT, where the two thienyl rings in the outmost BDT units are in the syn- and anti-fashion, are designed. Two decyl groups are introduced to their 6,13 and 7,14-positions to form four isomeric 6,13-syn-TBDT, 7,14-syn-TBDT, 6,13-anti-TBDT, and 7,14-anti-TBDT structures which are constructed by the DBU-induced 6-benzannulation involving propargyl-allenyl isomerization of the dieneyne moieties in the corresponding precursors followed by 6π-electrocyclization/aromatization, while isomeric TD-syn-TBDT and TD-anti-TBDT with four decyl groups substituted at 6,7,13,14-positions are synthesized via palladium-catalyzed dialkylacetylene insertion/C-H arylation of the corresponding iodobiaryl precursors. The intrinsic properties can be modulated by molecular manipulation of the main-chain and side-chain isomeric structures. anti-TBDT derivatives exhibit higher melting points, larger bandgaps, stronger intermolecular interactions, and higher mobility than the corresponding syn-TBDT analogues. These molecules can be further utilized as building blocks to make various TBDT-based materials for optoelectronic applications.

Donor-acceptor conjugated polymers based on multifused ladder-type arenes for organic solar cells.

Harvesting solar energy from sunlight to generate electricity is considered as one of the most important technologies to address the future sustainability of humans. Polymer solar cells (PSCs) have attracted tremendous interest and attention over the past two decades due to their potential advantage to be fabricated onto large area and light-weight flexible substrates by solution processing at a lower cost. PSCs based on the concept of bulk heterojunction (BHJ) configuration where an active layer comprises a composite of a p-type (donor) and an n-type (acceptor) material represents the most useful strategy to maximize the internal donor-acceptor interfacial area allowing for efficient charge separation. Fullerene derivatives such as [6,6]-phenyl-C61 or 71-butyric acid methyl ester (PCBM) are the ideal n-type materials ubiquitously used for BHJ solar cells. The major effort to develop photoactive materials is numerously focused on the p-type conjugated polymers which are generally synthesized by polymerization of electron-rich donor and electron-deficient acceptor monomers. Compared to the development of electron-deficient comonomers (acceptor segments), the development of electron-rich donor materials is considerably flourishing. Forced planarization by covalently fastening adjacent aromatic and heteroaromatic subunits leads to the formation of ladder-type conjugated structures which are capable of elongating effective conjugation, reducing the optical bandgap, promoting intermolecular π-π interactions and enhancing intrinsic charge mobility. In this review, we will summarize the recent progress on the development of various well-defined new ladder-type conjugated materials. These materials serve as the superb donor monomers to prepare a range of donor-acceptor semi-ladder copolymers with sufficient solution-processability for solar cell applications.

Sequence-controlled alternating block polychalcogenophenes: synthesis, structural characterization, molecular properties, and transistors for bromine detection.

Sequence-controlled polychalcogenophenes have attracted much interest in terms of synthesis, structure and function in polymer science. For the first time, we developed a new class of alternating block conjugated copolymers denoted as poly(alt-AB)x-b-(alt-AC)y where both blocks are constituted by an alternating copolymer. 3-Hexylthiophene (S), 3-hexylselenophene (Se) and 3-hexyltellurophene (Te) are used as A, B and C units to assemble three sequence-controlled polychalcogenophenes P(SSe)b(STe), P(SSe)b(SeTe) and P(STe)b(SeTe) which are prepared by adding two different Grignard monomers in sequence to carry out Ni(dppp)Cl2-catalyzed Kumada polymerization. The molecular weight, dispersity, and length of each block (x = y) and main-chain sequence can be synthetically controlled via the catalyst transfer polycondensation mechanism. The polymer structures, i.e. alternating block main chain with high side-chain regioregularity, are unambiguously confirmed by 1H-NMR and 13C-NMR. The optical and electrochemical properties of the polymers can be systematically fine-tuned by the composition and ratio of the chalcogenophenes. From GIWAXS measurements, all the polymers exhibited predominantly edge-on orientations, indicating that the packing behaviors of the alternating block polychalcogenophenes with high regioregularity are inherited from the highly crystalline P3HT. P(SSe)b(STe) exhibited a hole OFET mobility of 1.4 × 10-2 cm2 V-1 s-1, which represents one of the highest values among the tellurophene-containing polychalcogenophenes. The tellurophene units in the polymers can undergo Br2 addition to form the oxidized TeBr2 species which results in dramatically red-shifted absorption due to the alternating arrangement to induce strong charge transfer character. The OFET devices using the tellurophene-containing polychalcogenophenes can be applied for Br2 detection, showing high sensitivity, selectivity and reversibility.

Solution-Processable Donor-Acceptor Copolymer Thin Films for Efficient Visible-Light-Driven Photocatalytic Hydrogen Evolution.

Conjugated polymers (CPs) have been actively utilized as photocatalysts for hydrogen evolution due to their easy synthetic tunability to endow specific functionalities, including visible-light absorption, higher-lying LUMO energy for proton reduction, and sufficient photochemical stability. Enhancing interfacial surface and compatibility of hydrophobic CPs with hydrophilic water is the central focus to improve the hydrogen evolution rate (HER). Although a number of successful approaches have been developed in recent years, tedious chemical modifications or post-treatment of CPs make reproducibility of the materials difficult. In this work, a solution processable PBDB-T polymer is directly deposited on a glass substrate to form a thin film that is immersed in an aqueous solution to photochemically catalyze H2 generation. The PBDB-T thin film showed a much higher hydrogen evolution rate (HER) than the typical method of using PBDB-T suspended solids due to the enhanced interfacial area with a more suitable solid-state morphology. When the thickness of the thin film is reduced to dramatically improve the utilization of the photocatalytic material, the 0.1 mg-based PBDB-T thin film exhibited an unprecedentedly high HER of 120.90 mmol h-1 g-1.

Alcohol-Soluble Zwitterionic 4-(Dimethyl(pyridin-2-yl)ammonio)butane-1-sulfonate Small Molecule as a Cathode Modifier for Nonfullerene Acceptor-Based Organic Solar Cells.

A new zwitterionic small molecule 4-(dimethyl(pyridin-2-yl)ammonio)butane-1-sulfonate (PAS), synthesized from 2-dimethylaminopyrindine (2-DMAP), was developed for the ITO cathode modifier. PAS and 2-DMAP dissolved in methanol can form a thin layer on ITO cathode by a simple spin-coating process. The heteroatom moieties in 2-DMAP (sp2 and sp3 nitrogen) and PAS (sp2 nitrogen and sulfonate ion) can coordinate to the ITO surface and decrease the ITO work function by the induced surface dipoles. The fullerene-based (PBDTT-FTTE:PC71BM) inverted OSCs using PAS and 2-DMAP interlayer can achieve PCEs of 8.95 and 8.26%, respectively, which are superior to the devices without a modifier (PCE = 3.25%) and comparable to the corresponding ZnO-based device (PCE = 8.57%). Nevertheless, 2-DMAP, like other nitrogen-containing polymer interlayer materials, turns out to be not applicable to inverted organic solar cells (I-OSCs) with IT-4F as the n-type electron acceptor because the amino group of 2-DMAP can act as a nucleophile to attack the end-group of IT-4F at the interface. The decomposition of IT-4F by 2-DMAP was carefully proved to be via retro-aldol condensation. As a result, the device (PBDBT-F:IT-4F) modified with 2-DMAP displayed a low PCE of 7.34%. The zwitterionic PAS with reduced nucleophilicity and basicity can modify the ITO surface without decomposing IT-4F. The PBDBT-F:IT-4F-based device modified with PAS maintained a high PCE of 11.41%. Most importantly, the PAS-based device using the well-known Y6 acceptor (PBDBT-F:Y6) can achieve a PCE of 13.82%. This new interfacial material can be universally applied to I-OSCs employing various A-D-A-type acceptors installed with the electrophilic 1,1-dicyanamethylene-5,6-difluoro-3-indanone (FIC) end-group.

Synthesis of Ring-Locked Tetracyclic Dithienocyclopentapyrans and Dibenzocyclopentapyran via 1,5-Hydride Shift and Copper-Catalyzed C-O Bond Formation for Nonfullerene Acceptors.

We discovered a unique synthetic route to construct 2H-pyran-containing tetracyclic dithienocyclopentapyran (DTCP) and dibenzocyclopentapyran (DBCP) architectures. The synthesis involves an acid-induced dehydration cyclization followed by a [1,5] hydride-shift isomerization to form a cyclopentanone moiety which was converted to the pyran-embedded tetracyclic products by a CuI-catalyzed intramolecular C-O bond formation in good yield. DTCP was used as a building block to prepare an acceptor-donor-acceptor (A-D-A) type n-type material DTCP-BC leading to a solar cell efficiency of 9.32%.

Combination of indene-C60 bis-adduct and cross-linked fullerene interlayer leading to highly efficient inverted polymer solar cells.

A poly(3-hexylthiophene) (P3HT)-based inverted solar cell using indene-C60 bis-adduct (ICBA) as the acceptor achieved a high open-circuit voltage of 0.82 V due to ICBA's higher-lying lowest unoccupied molecular orbital level, leading to an exceptional power-conversion efficiency (PCE) of 4.8%. By incorporating a cross-linked fullerene interlayer, C-PCBSD, to further modulate the interface characteristics, the ICBA:P3HT-based inverted device exhibited an improved short-circuit current and fill factor, yielding a record high PCE of 6.2%.

Highly efficient and stable inverted polymer solar cells integrated with a cross-linked fullerene material as an interlayer.

A novel PCBM-based n-type material, [6,6]-phenyl-C(61)-butyric styryl dendron ester (PCBSD), functionalized with a dendron containing two styryl groups as thermal cross-linkers, has been rationally designed and easily synthesized. In situ cross-linking of PCBSD was carried out by heating at a low temperature of 160 degrees C for 30 min to generate a robust, adhesive, and solvent-resistant thin film. This cross-linked network enables a sequential active layer to be successfully deposited on top of this interlayer to overcome the problem of interfacial erosion and realize a multilayer inverted device by all-solution processing. An inverted solar cell device based on an ITO/ZnO/C-PCBSD/P3HT:PCBM/PEDOT:PSS/Ag configuration not only achieves enhanced device characteristics, with an impressive PCE of 4.4%, but also exhibits an exceptional device lifetime without encapsulation; it greatly outperforms a reference device (PCE = 3.5%) based on an ITO/ZnO/P3HT:PCBM/PEDOT:PSS/Ag configuration without the interlayer. This C-PCBSD interlayer exerts multiple positive effects on both P3HT/C-PCBSD and PCBM/C-PCBSD localized heterojunctions at the interface of the active layer, including improved exciton dissociation efficiency, reduced charge recombination, decreased interface contact resistance, and induction of vertical phase separation to reduce the bulk resistance of the active layer as well as passivation of the local shunts at the ZnO interface. Moreover, this promising approach can be applied to another inverted solar cell, ITO/ZnO/C-PCBSD/PCPDTBT:PC(71)BM/PEDOT:PSS/Ag, using PCPDTBT as the p-type low-band-gap conjugated polymer to achieve an improved PCE of 3.4%. Incorporation of this cross-linked C(60) interlayer could become a standard procedure in the fabrication of highly efficient and stable multilayer inverted solar cells.

Pd(II)-Catalyzed Direct Dehydrogenative Mono- and Diolefination of Selenophenes.

Pd(II)-catalyzed dehydrogenative Heck olefination of selenophenes with a broad olefinic substrate scope and high functional group tolerance is demonstrated. Carbonyl-substituted and phenyl-substituted olefins with electron-donating (D) and electron-accepting (A) groups can be regioselectively installed at C2 of the selenophene. The 2-olefinated selenophenes can subsequently undergo a second oxidative olefination to rapidly produce a new class of symmetrical D-π-D or unsymmetrical D-π-A 2,5-diolefinated selenophene materials.

Synthesis of side-chain regioregular and main-chain alternating poly(bichalcogenophene)s and an ABC-type periodic poly(terchalcogenophene).

Three unsymmetrical diiodobichalcogenophenes SSeI2, STeI2, and SeTeI2 and a diiodoterchalcogenophene SSeTeI2 were prepared. Grignard metathesis of SSeI2, STeI2, SeTeI2, and SSeTeI2 occurred regioselectively at the lighter chalcogenophene site because of its relatively lower electron density and less steric bulk. Nickel-catalyzed Kumada catalyst-transfer polycondensation of these Mg species provided a new class of side-chain regioregular and main-chain AB-type alternating poly(bichalcogenophene)s-PSSe, PSTe, and PSeTe-through a chain-growth mechanism. The ring-walking of the Ni catalyst from the lighter to the heavier chalcogenophene facilitated subsequent oxidative addition, thereby suppressing the possibility of chain-transfer or chain-termination. More significantly, the Ni catalyst could walk over the distance of three rings (ca. 1 nm)-from a thiophene unit via a selenophene unit to a tellurophene unit-to form PSSeTe, the first ABC-type regioregular and periodic poly(terchalcogenophene) comprising three different types of 3-hexylchalcogenophenes.

Regio- and stereo-selective [4+4] photodimerization of angular-shaped dialkyltetracenedithiophene.

Angular-shaped dialkyltetracenedithiophenes (aTDTs) undergo [4+4] photodimerization in solution to form a butterfly-shaped skeleton. This reaction proceeds in a regio- and stereo-selective manner, forming only a single planosymmetric syn-[2,2]-daTDT out of six possible products. The photocycloaddition of aTDTs can take place topochemically in the thin-film state while maintaining regio- and stereo-selectivity. Stronger aliphatic dispersion forces and π-π interactions play important roles in forming the eclipsed dimeric complex that leads to the syn-[2,2]-daTDT isomer.

Mg Doped CuCrO2 as Efficient Hole Transport Layers for Organic and Perovskite Solar Cells.

The electrical and optical properties of the hole transport layer (HTL) are critical for organic and halide perovskite solar cell (OSC and PSC, respectively) performance. In this work, we studied the effect of Mg doping on CuCrO2 (CCO) nanoparticles and their performance as HTLs in OSCs and PSCs. CCO and Mg doped CCO (Mg:CCO) nanoparticles were hydrothermally synthesized. The nanoparticles were characterized by various experimental techniques to study the effect of Mg doping on structural, chemical, morphological, optical, and electronic properties of CCO. We found that Mg doping increases work function and decreases particle size. We demonstrate CCO and Mg:CCO as efficient HTLs in a variety of OSCs, including the first demonstration of a non-fullerene acceptor bulk heterojunction, and CH3NH3PbI3 PSCs. A small improvement of average short-circuit current density with Mg doping was found in all systems.

Isomerically Pure Benzothiophene-Incorporated Acceptor: Achieving Improved Voc and Jsc of Nonfullerene Organic Solar Cells via End Group Manipulation.

Benzene-based 1,1-dicyanomethylene-3-indanone (IC) derivatives have been widely utilized as the end-group to construct acceptor-donor-acceptor type nonfullerene acceptors (A-D-A type NFAs). The extension of the end-group conjugation of nonfullerene acceptors (NFAs) is a rational strategy to facilitate intermolecular stacking of the end-groups which are responsible for efficient electron transportation. A bicyclic benzothiophene-based end-group acceptor, 2-(3-oxo-2,3-dihydro-1H-benzo[b]cyclopenta[d]thiophen-1-ylidene)malononitrile, denoted as α-BC was designed and synthesized. The Knoevenagel condensation of the unsymmetrical 1,3-diketo-precursor with one equivalent of malononitrile selectively reacts with the keto group attached at the α-position of the thiophene unit, leading to the isomerically pure benzothiophene-fused α-BC. The well-defined α-BC with extended conjugation was condensed with three different ladder-type diformylated donors to form three new A-D-A NFAs named BDCPDT-BC, DTCC-BC, and ITBC, respectively. The corresponding IC-based BDCPDT-IC, DTCC-IC, and ITIC model compounds were also synthesized for comparison. The incorporation of the electron-rich benzothiophene unit in the end-group upshifts the lowest unoccupied molecular orbital energy levels of the NFAs, which beneficially enlarges the Voc values. On the other hand, the benzothiophene unit in α-BC not also imparts an optical transition in the shorter wavelengths around 340-400 nm for a better light harvesting ability but also promotes the antiparallel π-π stacking of the end-groups for efficient electron transport. The organic photovoltaic cell devices using a PBDB-T polymer and BC-based NFAs all showed the improved Voc and Jsc values. The BDCPDT-BC- and DTCC-BC-based devices exhibited a power conversion efficiency (PCE) of 10.82 and 10.74%, respectively, which outperformed the corresponding BDCPDT-IC-, and DTCC-IC-based devices (9.33 and 9.25%). More importantly, the ITBC-based device delivered the highest PCE of 12.07% with a Jsc of 19.90 mA/cm2, a Voc of 0.94 V, and an fill factor of 64.51%, representing a 14% improvement relative to the traditional ITIC-based device (10.05%).

Naphthobisthiadiazole-Based Selenophene-Incorporated Quarterchalcogenophene Copolymers for Field-Effect Transistors and Polymer Solar Cells.

In this research, we developed six new selenophene-incorporated naphthobisthiadiazole-based donor-acceptor polymers PNT2Th2Se-OD, PNT2Se2Th-OD, PNT4Se-OD, PNT2Th2Se-DT, PNT2Se2Th-DT, and PNT4Se-DT. The structure-property relationships have been systematically established through the comparison of their structural variations: (1) isomeric biselenophene/bithiophene arrangement between PNT2Th2Se and PNT2Se2Th polymers, (2) biselenophene/bithiophene and quarterselenophene donor units between PNT2Th2Se/PNT2Se2Th and PNT4Se polymers, and (3) side-chain modification between the 2-octyldodecylthiophene (OD)- and 2-decyltetradecyl (DT)-series polymers. The incorporation of selenophene units in the copolymers induces stronger charge transfer to improve the light-harvesting capability while maintaining the strong intermolecular interactions to preserve the intrinsic crystallinity for high carrier mobility. The organic field-effect transistor device using PNT2Th2Se-OD achieved a high hole mobility of 0.36 cm2 V-1 s-1 with an on/off ratio of 1.9 × 105. The solar cells with PNT2Th2Se-OD:PC71BM exhibited a power conversion efficiency of 9.47% with a Voc of 0.68 V, an fill factor of 67%, and an impressive Jsc of 20.69 mA cm-2.

Synthesis of unsymmetrical benzotrichalcogenophenes by N-heterocyclic carbene-palladium-catalyzed intramolecular direct C3-arylation of chalcogenophenes.

A series of new unsymmetrical benzotrichalcogenophenes (BTCs) were synthesized by the Pd-N-heterocyclic carbene catalyzed intramolecular C3-arylation of furan, thiophene, selenophene and tellurophene units. This is the first time that a C3-direct arylation of selenophene and tellurophene moieties has ever been demonstrated.

Cross-linked Triarylamine-Based Hole-Transporting Layer for Solution-Processed PEDOT:PSS-Free Inverted Perovskite Solar Cells.

The device performance of inverted organic metallohalide perovskite solar cells (OMPSCs) is optimized via tailoring the electrode surfaces with electron- and hole-transporting materials. This work demonstrates the fabrication of PEDOT:PSS-free OMPSCs using a hole-transporting composite material consisting of bilayered vanadium oxide (VO x) and a thermally cross-linked triarylamine-based material X-DVTPD, which contributes to higher Voc and Jsc values. The hydrophobicity of X-DVTPD resulted in the formation of large perovskite crystals and enhanced the stability of OMPSCs. Integration of ionic fullerene derivative, fulleropyrrolidinium iodide, in OMPSCs as a hole-blocking interfacial layer at the interface with Ag proves effective to further boost the device efficiency to 18.08%.

Phenyltetraene-based nonlinear optical chromophores with enhanced chemical stability and electrooptic activity.

"Push-pull" phenyltetraene-based chromophores are too sensitive to be incorporated into Diels-Alder-type cross-linkable polymers due to the reactivity of its diene segment with maleimides. A facile synthetic route has been explored to incorporate a methoxy group into the R position of such chromophores, which reduces their diene reactivity during the poling and lattice hardening process. The poled polymers with one of such chromophores doped in a cross-linked polymer lattice showed ultrahigh electro-optic activities, up to 306 pm/V at 1310 nm.