Influence of Backbone Fluorination in Regioregular Poly(3-alkyl-4-fluoro)thiophenes

Conformational Analysis of Conjugated Organic Materials: What Are My Heteroatoms Really Doing?

Organic semiconductor small molecules and polymers often incorporate heteroatoms into their chemical structures to affect the electronic properties of the material. A particular design philosophy has been to use these heteroatoms to influence torsional potentials, since the overlap of adjacent π-orbitals is most efficient in planar systems and is critical for charge delocalization in these systems. Since these design rules became popular, the messages from the earlier works have become lost in a sea of reports of "conformational locks", where the non-covalent interactions have relatively small contributions to planarizing torsional potentials. Greater influences can be found in the stabilization by extended conjugation, consideration of steric repulsion, and the interactions involving solubilizing chains and neighboring molecules or polymer chains in condensed phases.

Real-time correlation of crystallization and segmental order in conjugated polymers

Modulating the segmental order in the morphology of conjugated polymers is widely recognized as a crucial factor for achieving optimal electronic properties and mechanical deformability. However, it is worth noting that the segmental order is typically associated with the crystallization process, which can result in rigid and brittle long-range ordered crystalline domains. To precisely control the morphology, a comprehensive understanding of how highly anisotropic conjugated polymers form segmentally ordered structures with ongoing crystallization is essential, yet currently elusive. To fill this knowledge gap, we developed a novel approach with a combination of stage-type fast scanning calorimetry and micro-Raman spectroscopy to capture the series of specimens with a continuum in the polymer percent crystallinity and detect the segmental order in real-time. Through the investigation of conjugated polymers with different backbones and side-chain structures, we observed a generally existing phenomenon that the degree of segmental order saturates before the maximum crystallinity is achieved. This disparity allows the conjugated polymers to achieve good charge carrier mobility while retaining good segmental dynamic mobility through the tailored treatment. Moreover, the crystallization temperature to obtain optimal segmental order can be predicted based on Tg and Tm of conjugated polymers. This in-depth characterization study provides fundamental insights into the evolution of segmental order during crystallization, which can aid in designing and controlling the optoelectronic and mechanical properties of conjugated polymers.

Coplanar Conformational Structure of π-Conjugated Polymers for Optoelectronic Applications

Hierarchical structure of conjugated polymers is critical to dominating their optoelectronic properties and applications. Compared to nonplanar conformational segments, coplanar conformational segments of conjugated polymers (CPs) demonstrate favorable properties for applications as a semiconductor. Herein, recent developments in the coplanar conformational structure of CPs for optoelectronic devices are summarized. First, this review comprehensively summarizes the unique properties of planar conformational structures. Second, the characteristics of the coplanar conformation in terms of optoelectrical properties and other polymer physics characteristics are emphasized. Five primary characterization methods for investigating the complanate backbone structures are illustrated, providing a systematical toolbox for studying this specific conformation. Third, internal and external conditions for inducing the coplanar conformational structure are presented, offering guidelines for designing this conformation. Fourth, the optoelectronic applications of this segment, such as light-emitting diodes, solar cells, and field-effect transistors, are briefly summarized. Finally, a conclusion and outlook for the coplanar conformational segment regarding molecular design and applications are provided.

Theoretical investigation of novel electron donors for bulk heterojunction solar cells with potential photovoltaic characteristics

Engineering electronic organic donor materials are one of the most critical steps in producing bulk-heterojunction solar cells (BHJ) with good photovoltaic properties. Compared to standard donor materials, electron donors derived from thiophene have made significant progress as they can be better suited for optoelectronics and are cheaper and more stable. Therefore, the use of new thiophene derivatives (M1-M4) as donor molecules in BHJs has been the subject of this extensive theoretical analysis. Density functional theory (DFT) and time-dependent DFT (TD-DFT) computations have been used to investigate the boundary molecular orbital (FMO) analysis, the density of states analysis, electron and hole reorganization energy, molecular electrostatic potential, global reactivity parameters, and photovoltaic properties. The effects of end-donor modifications on the photovoltaic and electronic characteristics of the new molecules (M1-M4) are investigated. According to the results, the molecules have good optical properties, a small band gap, a perfect open-circuit voltage, and a good alignment energy level between the designated donor molecules and the acceptor phenyl-C61-butyric acid methyl ester (PCBM). These results suggest that further research in this area could enhance the efficacy of organic solar cells.

Subtle Molecular Changes Largely Modulate Chiral Helical Assemblies of Achiral Conjugated Polymers by Tuning Solution-State Aggregation

Understanding the solution-state aggregate structure and the consequent hierarchical assembly of conjugated polymers is crucial for controlling multiscale morphologies during solid thin-film deposition and the resultant electronic properties. However, it remains challenging to comprehend detailed solution aggregate structures of conjugated polymers, let alone their chiral assembly due to the complex aggregation behavior. Herein, we present solution-state aggregate structures and their impact on hierarchical chiral helical assembly using an achiral diketopyrrolopyrrole-quaterthiophene (DPP-T4) copolymer and its two close structural analogues wherein the bithiophene is functionalized with methyl groups (DPP-T2M2) or fluorine atoms (DPP-T2F2). Combining in-depth small-angle X-ray scattering analysis with various microscopic solution imaging techniques, we find distinct aggregate in each DPP solution: (i) semicrystalline 1D fiber aggregates of DPP-T2F2 with a strongly bound internal structure, (ii) semicrystalline 1D fiber aggregates of DPP-T2M2 with a weakly bound internal structure, and (iii) highly crystalline 2D sheet aggregates of DPP-T4. These nanoscopic aggregates develop into lyotropic chiral helical liquid crystal (LC) mesophases at high solution concentrations. Intriguingly, the dimensionality of solution aggregates largely modulates hierarchical chiral helical pitches across nanoscopic to micrometer scales, with the more rigid 2D sheet aggregate of DPP-T4 creating much larger pitch length than the more flexible 1D fiber aggregates. Combining relatively small helical pitch with long-range order, the striped twist-bent mesophase of DPP-T2F2 composed of highly ordered, more rigid 1D fiber aggregate exhibits an anisotropic dissymmetry factor (g-factor) as high as 0.09. This study can be a prominent addition to our knowledge on a solution-state hierarchical assembly of conjugated polymers and, in particular, chiral helical assembly of achiral organic semiconductors that can catalyze an emerging field of chiral (opto)electronics.

Intermolecular Interactions, Morphology, and Photovoltaic Patterns in p-i-n Heterojunction Solar Cells With Fluorine-Substituted Organic Photovoltaic Materials

During the layer-by-layer (LBL) processing of polymer solar cells (PSCs), the swelling and molecule interdiffusion are essential for achieving precise, controllable vertical morphology, and thus efficient PSCs. However, the influencing mechanism of material properties on morphology and correlated device performance has not been paid much attention. Herein, a series of fluorinated/non-fluorinated polymer donors (PBDB-T and PBDB-TF) and non-fullerene acceptors (ITIC, IT-2F, and IT-4F) are employed to investigate the performance of LBL devices. The impacts of fluorine substitution on the repulsion and miscibility between the donor and acceptor, as well as the molecular arrangement of the donor/acceptor and the vertical distribution of the LBL devices are systematically explored by the measurement of donor/acceptor Flory-Huggins interaction parameters, spectroscopic ellipsometry, and neutron reflectivity, respectively. With efficient charge transfer due to the ideal vertical and horizon morphology properties, devices based on PBDB-TF/IT-4F exhibit the highest fill factors (FFs) as well as champion power conversion efficiencies (PCEs). With this guidance, high-performance LBL devices with PCE of 17.2%, 18.5%, and 19.1% are obtained by the fluorinated blend of PBDB-TF/Y6, PBDB-TF/L8-BO, and D18/L8-BO respectively.

Interplay between Side Chain Density and Polymer Alignment: Two Competing Strategies for Enhancing the Thermoelectric Performance of P3HT Analogues

A series of polythiophenes with varying side chain density was synthesized, and their electrical and thermoelectric properties were investigated. Aligned and non-aligned thin films of the polymers were characterized in the neutral and chemically doped states. Optical and diffraction measurements revealed an overall lower order in the thin films with lower side chain density, also confirmed using polarized optical experiments on aligned thin films. However, upon doping the non-aligned films, a sixfold increase in electrical conductivity was observed for the polythiophene with the lowest side chain density compared to poly(3-hexylthiophene) (P3HT). We found that the improvement in conductivity was not due to a larger charge carrier density but an increase in charge carrier mobility after doping with 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4TCNQ). On the other hand, doped aligned films did not show the same trend; lower side chain density instead led to a lower conductivity and Seebeck coefficient compared to those for P3HT. This was attributed to the poorer alignment of the polymer thin films with lower side chain density. The study demonstrates that optimizing side chain density is a synthetically simple and effective way to improve electrical conductivity in polythiophene films relevant to thermoelectric applications.

Hole-limited electrochemical doping in conjugated polymers

Simultaneous transport and coupling of ionic and electronic charges is fundamental to electrochemical devices used in energy storage and conversion, neuromorphic computing and bioelectronics. While the mixed conductors enabling these technologies are widely used, the dynamic relationship between ionic and electronic transport is generally poorly understood, hindering the rational design of new materials. In semiconducting electrodes, electrochemical doping is assumed to be limited by motion of ions due to their large mass compared to electrons and/or holes. Here, we show that this basic assumption does not hold for conjugated polymer electrodes. Using operando optical microscopy, we reveal that electrochemical doping speeds in a state-of-the-art polythiophene can be limited by poor hole transport at low doping levels, leading to substantially slower switching speeds than expected. We show that the timescale of hole-limited doping can be controlled by the degree of microstructural heterogeneity, enabling the design of conjugated polymers with improved electrochemical performance.

Semi-conductive micellar networks of all-conjugated diblock and triblock copolymer blends

The crystallization-driven self-assembly of the blends of the all-conjugated block copolymers of poly(3-hexylthiophene) (P3HT) and poly(3-ethylhexylthiophene) (P3EHT) results in the cross-linking of the one-dimensional nanowires of P3HT-b-P3EHT, which is achieved by intercalating P3HT-b-P3EHT-b-P3HT into the nanowire cores. The micellar networks constitute flexible and porous materials that conduct electricity upon doping.

Synergistic Contribution of Oligo(ethylene glycol) and Fluorine Substitution of Conjugated Polymer Photocatalysts toward Solar Driven Sacrificial Hydrogen Evolution

To separately explore the importance of hydrophilicity and backbone planarity of polymer photocatalyst, a series of benzothiadiazole-based donor-acceptor alternating copolymers incorporating alkoxy, linear oligo(ethylene glycol) (OEG) side chain, and backbone fluorine substituents is presented. The OEG side chains in the polymer backbone increase the surface energy of the polymer nanoparticles, thereby improving the interaction with water and facilitating electron transfer to water. Moreover, the OEG-attached copolymers exhibit enhanced intermolecular packing compared to polymers with alkoxy side chains, which is possibly attributed to the self-assembly properties of the side chains. Fluorine substituents on the polymer backbone produce highly ordered lamellar stacks with distinct π-π stacking features; subsequently, the long-lived polarons toward hydrogen evolution are observed by transient absorption spectroscopy. In addition, a new nanoparticle synthesis strategy using a methanol/water mixed solvent is first adopted, thereby avoiding the screening effect of surfactants between the nanoparticles and water. Finally, hydrogen evolution rate of 26 000 µmol g^-1  h^-1 is obtained for the copolymer incorporated with both OEG side chains and fluorine substituents under visible-light irradiation (λ > 420 nm). This study demonstrates how the glycol side chain strategy can be further optimized for polymer photocatalysts by controlling the backbone planarity.

Crystallization of D-A Conjugated Polymers: A Review of Recent Research

D-A conjugated polymers are key materials for organic solar cells and organic thin-film transistors, and their film structure is one of the most important factors in determining device performance. The formation of film structure largely depends on the crystallization process, but the crystallization of D-A conjugated polymers is not well understood. In this review, we attempted to achieve a clearer understanding of the crystallization of D-A conjugated polymers. We first summarized the features of D-A conjugated polymers, which can affect their crystallization process. Then, the crystallization process of D-A conjugated polymers was discussed, including the possible chain conformations in the solution as well as the nucleation and growth processes. After that, the crystal structure of D-A conjugated polymers, including the molecular orientation and polymorphism, was reviewed. We proposed that the nucleation process and the orientation of the nuclei on the substrate are critical for the crystal structure. Finally, we summarized the possible crystal morphologies of D-A conjugated polymers and explained their formation process in terms of nucleation and growth processes. This review provides fundamental knowledge on how to manipulate the crystallization process of D-A conjugated polymers to regulate their film structure.

Fluorination-Induced Charge Trapping and Operational Instability in Conjugated-Polymer Field-Effect Transistors

Fluorination of a conjugated polymer backbone is an effective strategy to control the microstructure and electronic structure of a conjugated polymer. Although fluorination has been widely reported to increase charge carrier mobility, its effect on the operational stability of electronic devices has not been extensively investigated. Here, the effect of fluorination of a conjugated polymer backbone on charge trapping and the operational stability of organic field-effect transistors is investigated. The results show that the device based on a fluorinated conjugated polymer exhibits relatively poor operational stability despite its greater charge carrier mobility compared with that in the device based on its nonfluorinated polymer counterpart. Experimental results reveal that the low stability originates from the greater degree of shallow trapping of charge carriers within the fluorinated polymer thin film and that the shallow trapping is closely related to the presence of minority charge carriers. A mechanism of charge trapping is proposed.

Group 16 conjugated polymers based on furan, thiophene, selenophene, and tellurophene

Five-membered aromatic rings containing Group 16 elements (O, S, Se, and Te), also referred as chalcogenophenes, are ubiquitous building blocks for π-conjugated polymers (CPs). Among these, polythiophenes have been established as a model system to study the interplay between molecular structure, solid-state organization, and electronic performance. The judicious substitution of alternative heteroatoms into polythiophenes is a promising strategy for tuning their properties and improving the performance of derived organic electronic devices, thus leading to the recent abundance of CPs containing furan, selenophene, and tellurophene. In this review, we first discuss the current status of Kumada, Negishi, Murahashi, Suzuki-Miyaura, and direct arylation polymerizations, representing the best routes to access well-defined chalcogenophene-containing homopolymers and copolymers. The self-assembly, optical, solid-state, and electronic properties of these polymers and their influence on device performance are then summarized. In addition, we highlight post-polymerization modifications as effective methods to transform polychalcogenophene backbones or side chains in ways that are unobtainable by direct polymerization. Finally, the major challenges and future outlook in this field are presented.

Influence of Fluorine Substitution on the Photovoltaic Performance of Wide Band Gap Polymer Donors for Polymer Solar Cells

The design and development of wide band gap (WBG) polymer donors are critical for achieving high power conversion efficiencies (PCEs) in polymer solar cells. In this work, four WBG polymer donors, Q4, Q5, Q6, and Q7, with different numbers and positions of fluorine substitution (n = 0, 2, 2, and 4, respectively) were prepared, and the effect of fluorination on their photovoltaic performance was systematically investigated. When blended with a small-molecule electron acceptor MeIC, the devices based on Q4, Q5, Q6, and Q7 showed PCEs of 10.34, 11.06, 5.26, and 0.48%, respectively. When coupled with a low band gap polymer acceptor PYIT to fabricate all-polymer solar cells (all-PSCs), while the other three polymers (Q5-Q7) exhibited much lower PCEs in the range of 0.12-6.71%, the Q4 polymer-based all-PSCs showed the highest PCE of 15.06%, comparable to that of the devices fabricated with the star polymer donor PM6 (PCE = 15.00%). Detailed physicochemical and morphological studies revealed that an over-substitution of F in Q7 results in undesired low-lying HOMO levels and phase separation with the acceptors, thus resulting in its inferior PCEs. Moreover, the less F-substitution and controlling of the positions of F-substitution position in Q4 and Q5 can improve the HOMO energy level matching as well as morphologies between these two polymers with the acceptors, which in turn gives rise to higher performances. Clearly, our results indicate that Q4 is a promising donor candidate for high-performance all-PSCs, and the fine-tuning of both the number and positions of F-substitution in the polymer backbone is essential in developing high-performance WBG polymer donors.

Stepwise on-surface synthesis of thiophene-based polymeric ribbons by coupling reactions and the carbon-fluorine bond cleavage

The rational synthesis of thiophene-based cross-coupled polymers on surfaces has been attracting more attention recently. Here, we report the stepwise activation of 5,5'-(2,3-difluoro-1,4-phenylene)bis(2-bromothiophene) as a precursor to synthesize thiophene-based polymeric ribbons on the Au(111) surface. Scanning tunneling microscopy studies showed that the precursor adopted different conformations in the self-assembled structure, organometallic species, and covalent polymers. On annealing the sample at a relatively low temperature (150 °C), the conversion of the organometallic structure into a covalent product with straight lines was observed, in which the Br adatoms arranged between the neighboring chains. On further annealing the sample at 270 °C, the detached Br adatoms played a key role in promoting the C-H bond activation. The cross-linked polymer was achieved by a combination of Ullmann and dehydrogenative coupling. When the annealing temperature was up to 390 °C, the C-F bond activation was triggered, which led to the formation of polymeric ribbons resulting from the cyclodehydrogenation of the fluorinated polymer. This study further supplements the reaction mechanism of thiophene-based dehalogenative, dehydrogenative and defluorinative coupling, and provides us a rational way for synthesizing cross-linked functional materials.

The Halogenation Effects of Electron Acceptor ITIC for Organic Photovoltaic Nano-Heterojunctions

Molecular engineering plays a critical role in the development of electron donor and acceptor materials for improving power conversion efficiency (PCE) of organic photovoltaics (OPVs). The halogenated acceptor materials in OPVs have shown high PCE. Here, to investigate the halogenation mechanism and the effects on OPV performances, based on the density functional theory calculations with the optimally tuned screened range-separated hybrid functional and the consideration of solid polarization effects, we addressed the halogenation effects of acceptor ITIC, which were modeled by bis-substituted ITIC with halogen and coded as IT-2X (X = F, Cl, Br), and PBDB-T:ITIC, PBDB-T:IT-2X (X = F, Cl, Br) complexes on their geometries, electronic structures, excitations, electrostatic potentials, and the rate constants of charge transfer, exciton dissociation (ED), and charge recombination processes at the heterojunction interface. The results indicated that halogenation of ITIC slightly affects molecular geometric structures, energy levels, optical absorption spectra, exciton binding energies, and excitation properties. However, the halogenation of ITIC significantly enlarges the electrostatic potential difference between the electron acceptor and donor PBDB-T with the order from fluorination and chlorination to bromination. The halogenation also increases the transferred charges of CT states for the complexes. Meanwhile, the halogenation effects on CT energies and electron process rates depend on different haloid elements. No matter which kinds of haloid elements were introduced in the halogenation of acceptors, the ED is always efficient in these OPV devices. This work provides an understanding of the halogenation mechanism, and is also conducive to the designing of novel materials with the aid of the halogenation strategy.

n-Type Organic and Polymeric Semiconductors Based on Bithiophene Imide Derivatives

ConspectusIn the last three decades, p-type (hole-transporting) organic and polymeric semiconductors have achieved great success in terms of materials diversity and device performance, while the development of n-type (electron-transporting) analogues greatly lags behind, which is limited by the scarcity of highly electron-deficient building blocks with compact geometry and good solubility. However, such n-type semiconductors are essential due to the existence of the p-n junction and a complementary metal oxide semiconductor (CMOS)-like circuit in organic electronic devices. Among various electron-deficient building blocks, imide-functionalized arenes, such as naphthalene diimide (NDI) and perylene diimide (PDI), have been proven to be the most promising ones for developing n-type organic and polymeric semiconductors. Nevertheless, phenyl-based NDI and PDI lead to sizable steric hindrance with neighboring (hetero)arenes and a high degree of backbone distortion in the resultant semiconductors, which greatly limits their microstructural ordering and charge transport. To attenuate the steric hindrance associated with NDI and PDI, a novel imide-functionalized heteroarene, bithiophene imide (BTI), was designed; however, the BTI-based semiconductors suffer from high-lying frontier molecular orbital (FMO) energy levels as a result of their electron-rich thiophene framework and monoimide group, which is detrimental to n-type performance.In this Account, we review a series of BTI derivatives developed via various strategies, including ring fusion, thiazole substitution, fluorination, cyanation, and chalcogen substitution, and elaborate the synthesis routes designed to overcome the synthesis challenges due to their high electron deficiency. After structural optimization, these BTI derivatives can not only retain the advantages of good solubility, a planar backbone, and small steric hindrance inherited from BTI but also have greatly suppressed FMO levels. These novel building blocks enable the construction of a great number of n-type organic and polymeric semiconductors, particularly acceptor-acceptor (or all-acceptor)-type polymers, with remarkable performance in various devices, including electron mobility (μ_e) of 3.71 cm² V^-1 s^-1 in organic thin-film transistors (OTFTs), a power conversion efficiency (PCE) of 15.2% in all-polymer solar cells (all-PSCs), a PCE of 20.8% in inverted perovskite solar cells (PVSCs), electrical conductivity (σ) of 0.34 S cm^-1 and a power factor (PF) of 1.52 μW m^-1 K^-2 in self-doped diradicals, and σ of 23.3 S cm^-1 and a PF of ∼10 μW m^-1 K^-2 in molecularly n-doped polymers, all of which are among the best values in each type of device. The structure-property-device performance correlations of these n-type semiconductors are elucidated. The design strategy and synthesis of these novel BTI derivatives provide important information for developing highly electron-deficient building blocks with optimized physicochemical properties. Finally, we offer our insights into the further development of BTI derivatives and semiconductors built from them.

Raising Dielectric Permittivity Mitigates Dopant-Induced Disorder in Conjugated Polymers

Conjugated polymers need to be doped to increase charge carrier density and reach the electrical conductivity necessary for electronic and energy applications. While doping increases carrier density, Coulomb interactions between the dopant molecules and the localized carriers are poorly screened, causing broadening and a heavy tail in the electronic density-of-states (DOS). The authors examine the effects of dopant-induced disorder on two complimentary charge transport properties of semiconducting polymers, the Seebeck coefficient and electrical conductivity, and demonstrate a way to mitigate them. Their simulations, based on a modified Gaussian disorder model with Miller-Abrahams hopping rates, show that dopant-induced broadening of the DOS negatively impacts the Seebeck coefficient versus electrical conductivity trade-off curve. Increasing the dielectric permittivity of the polymer mitigates dopant-carrier Coulomb interactions and improves charge transport, evidenced by simultaneous increases in conductivity and the Seebeck coefficient. They verified this increase experimentally in iodine-doped P3HT and P3HT blended with barium titanate (BaTiO3 ) nanoparticles. The addition of 2% w/w BaTiO3 nanoparticles increased conductivity and Seebeck across a broad range of doping, resulting in a fourfold increase in power factor. Thus, these results show a promising path forward to reduce the dopant-charge carrier Coulomb interactions and mitigate their adverse impact on charge transport.

Preparing polythiophene derivative with alternating alkyl and thioalkyl side chains via Kumada coupling for efficient organic solar cells

A polythiophene, namely PTST with alternating alkyl and thioalkyl side chains, is prepared by Kumada catalyst-transfer polycondensation. PTST can hierarchically pre-aggregate in solution, and then form a favorable morphology in organic solar cells.

Excited state dynamics and exciton diffusion in triphenylamine/dicyanovinyl push-pull small molecule for organic optoelectronics

Triphenylamine-based small push–pull molecules have recently attracted substantial research attention due to their unique optoelectronic properties. Here, we investigate the excited state de-excitation dynamics and exciton diffusion in TPA-T-DCV-Ph-F small molecule, having simple chemical structure with asymmetrical architecture and end-capped with electron-withdrawing p-fluorodicyanovinyl group. The excited state lifetime in diluted solutions (0.04 ns in toluene and 0.4 ns in chloroform) are found to be surprisingly shorter compared to the solid state (3 ns in PMMA matrix). Time-dependent density functional theory indicates that this behavior originates from non-radiative relaxation of the excited state through a conical intersection between the ground and singlet excited state potential energy surfaces. Exciton diffusion length of ~ 16 nm in solution processed films was retrieved by employing time-resolved photoluminescence volume quenching measurements with Monte Carlo simulations. As means of investigating the device performance of TPA-T-DCV-Ph-F, we manufactured solution and vacuum processed bulk heterojunction solar cells that yielded efficiencies of ~ 1.5% and ~ 3.7%, respectively. Our findings demonstrate that the short lifetime in solutions does not hinder per se long exciton diffusion length in films thereby granting applications of TPA-T-DCV-Ph-F and similar push–pull molecules in vacuum and solution processable devices.

Pyrrolo[3,2-b]pyrrole-1,4-dione (IsoDPP) End Capped with Napthalimide or Phthalimide: Novel Small Molecular Acceptors for Organic Solar Cells

We introduce two novel solution-processable electron acceptors based on an isomeric core of the much explored diketopyrrolopyrrole (DPP) moiety, namely pyrrolo[3,2-b]pyrrole-1,4-dione (IsoDPP). The newly designed and synthesized compounds, 6,6'-[(1,4-bis{4-decylphenyl}-2,5-dioxo-1,2,4,5-tetrahydropyrrolo[3,2-b]pyrrole-3,6-diyl)bis(thiophene-5,2-diyl)]bis[2-(2-butyloctyl)-1H-benzo[de]isoquinoline-1,3(2H)-dione] (NAI-IsoDPP-NAI) and 5,5'-[(1,4-bis{4-decylphenyl}-2,5-dioxo-1,2,4,5-tetrahydropyrrolo[3,2-b]pyrrole-3,6-diyl)bis(thiophene-5,2-diyl)]bis[2-(2-butyloctyl)isoindoline-1,3-dione] (PI-IsoDPP-PI) have been synthesized via Suzuki couplings using IsoDPP as a central building block and napthalimide or phthalimide as end-capping groups. The materials both exhibit good solubility in a wide range of organic solvents including chloroform (CF), dichloromethane (DCM), and tetrahydrofuran (THF), and have a high thermal stability. The new materials absorb in the wavelength range of 300-600 nm and both compounds have similar electron affinities, with the electron affinities that are compatible with their use as acceptors in donor-acceptor bulk heterojunction (BHJ) organic solar cells. BHJ devices comprising the NAI-IsoDPP-NAI acceptor with poly(3-n-hexylthiophene) (P3HT) as the donor were found to have a better performance than the PI-IsoDPP-PI containing cells, with the best device having a VOC of 0.92 V, a JSC of 1.7 mAcm-2, a FF of 63%, and a PCE of 0.97%.

Synthesis, Characterization, and Charge-Transport Properties of Halogenated Dibenzo[a,j]perylenes

In designing organic semiconductors for organic devices, halogenation is a very popular strategy for tuning the electronic properties and packing arrangement in the solid state. Herein, we report the synthesis and characterization of halogenated dibenzo[a,j]perylene (DBP) with triethylsilyl (TES)-ethynyl substituents at the 8- and 16-positions (TES-DBP). The resulting compounds are characterized by optical, electrochemical, crystallographic, and computational studies to clarify the effect of halogenation on the optoelectronic properties and charge-carrier transport. It is found that the halogen atoms, the degree of halogenation, and their positional locations can alter the electronic properties and crystal packing of the compounds. In contrast to fluorinated TES-DBP, the chlorinated counterpart has red-shifted maximum absorption and lower electron affinity owing to the electron delocalization between DBP core and the unoccupied 3d orbitals of Cl atom. Organic field-effect transistor measurements demonstrate that TES-2ClDBP shows a hole mobility of 0.25 cm² V^-1 s^-1, which is higher than TES-2FDBP and TES-DBP. On the other hand, TES-4ClDBP exhibits ambipolar transport characteristics with electron and hole mobilities up to 0.02 and 0.07 cm² V^-1 s^-1, respectively.

Finely Designed P3HT-Based Fully Conjugated Graft Polymer: Optical Measurements, Morphology, and the Faraday Effect

In this work, our group synthesized and characterized a fully conjugated graft polymer comprising of a donor-acceptor molecular backbone and regioregular poly(3-hexylthiophene) (RRP3HT) side chains. Here, our macromonomer (MM) was synthesized via Kumada catalyst transfer polycondensation reaction based on ditin-benzodithiophene (BDT) initiator. The tin content of MM was then investigated by inductively coupled plasma-mass spectrometry (ICP-MS), which allowed for accurate control of donor/acceptor monomer ratio of 1:1 for the following Stille coupling polymerization toward our graft polymer (BP). The structures of the polymers were then characterized by gel permeation chromatography (GPC), NMR, and elemental analysis. This was followed by the characterization of optical, electrochemical, and physical properties. The magneto-optical activity of graft polymer BP was then measured. It was found that, despite the presence of the acceptor backbone, the characteristic large Faraday rotation of RRP3HT was maintained in polymer BP, which exhibited a Verdet constant of 2.39 ± 0.57 (10⁴) °/T·m.

Impact of Polymer Backbone Fluorination on the Charge Generation/Recombination Patterns and Vertical Phase Segregation in Bulk Heterojunction Organic Solar Cells

Incorporating fluorine (-F) substituents along the main-chains of polymer donors and acceptors is an effective strategy toward efficient bulk-heterojunction (BHJ) solar cells. Specifically, F-substituted polymers often exhibit planar conformations, leading to favorable packing, and electronic coupling. However, the effects of fluorine substituents on the charge generation and recombination characteristics that determine the overall efficiency of BHJ active layers remain critically important issues to examine. In this report, two PBDT[2X]T polymer analogs -poly[4,8-bis((2-ethylhexyl)oxy)benzo[1,2-b:4, 5-b']dithiophene-thiophene] [PBDT[2H]T] and its F-substituted counterpart poly[4,8-bis((2-ethylhexyl)oxy)benzo[1,2-b:4,5-b']dithiophene-3,4-difluoro-thiophene] [PBDT[2F]T]-are studied to systematically examine how -F substituents impact the blend morphology, charge generation, carrier recombination and extraction in BHJ solar cells. Considering the large efficiency differences between PBDT[2H]T- and PBDT[2F]T-based BHJ devices, significant emphasis is given to characterizing the out-of-plane morphology of the blend films as vertical phase-separation characteristics are known to have dramatic effects on charge transport and carrier extraction in polymer-fullerene BHJ solar cells. Herein, we use electron energy loss spectroscopy (EELS) in tandem with charge transport characterization to examine PBDT[2X]T-fullerene blend films. Our analyses show that PBDT[2H]T and PBDT[2F]T possess very different charge generation, recombination and extraction characteristics, resulting from distinct aggregation, and phase-distribution within the BHJ blend films.

Crucial Role of Fluorine in Fully Alkylated Ladder-Type Carbazole-Based Nonfullerene Organic Solar Cells

Two fused ladder-type nonfullerene acceptors, DTCCIC and DTCCIC-4F, based on an electron-donating alkylated dithienocyclopentacarbazole core flanked by electron-withdrawing nonfluorinated or fluorinated 1,1-dicyanomethylene-3-indanone (IC or IC-4F), are prepared and utilized in organic solar cells (OSCs). The two new molecules reveal planar structures and strong aggregation behavior, and fluorination is shown to red-shift the optical band gap and downshift energy levels. OSCs based on DTCCIC-4F exhibit a power conversion efficiency of 12.6%, much higher than that of DTCCIC-based devices (6.2%). Microstructural studies reveal that while both acceptors are highly crystalline, bulk heterojunction blends based on the nonfluorinated DTCCIC result in overly coarse domains, while blends based on the fluorinated DTCCIC-4F exhibit a more optimal nanoscale morphology. These results highlight the importance of end group fluorination in controlling molecular aggregation and miscibility.

Recent developments in the synthesis of regioregular thiophene-based conjugated polymers for electronic and optoelectronic applications using nickel and palladium-based catalytic systems

Thiophene-based conjugated polymers are important conjugated polymers due to their exceptional optical and conductive properties, over the past few decades many researchers have designed novel strategies to reach more efficient materials for electronic applications.

Branched versus linear: side-chain effect on fluorinated wide bandgap donors and their applications in organic solar cells

We report a new series of wide band-gap small organic molecules as donor-materials featuring an indaceno[1,2-b:5,6-b′]dithiophene (IDT) core and fluorinated thiophene linkers for solution-processed organic solar cells.

Efficient Debundling of Few-Walled Carbon Nanotubes by Wrapping with Donor-Acceptor Polymers for Improving Thermoelectric Properties

Organic thermoelectric (TE) materials have great potential as sustainable energy sources for powering flexible and wearable electronic devices via harvesting of human body heat. Recent advances in soluble conjugated polymer/carbon nanotube (CNT) composites have facilitated achievement of high TE power factors. However, the effects of conjugated polymers on the debundling and electrical percolation of CNTs and on the TE properties of their composites are not yet fully understood. Herein, we introduce a novel type of polymer/CNT composite composed of a donor-acceptor (D-A)-type polymer and few-walled CNTs (FWCNTs). Three kinds of D-A polymers are employed to disperse FWCNTs, and the photophysical, morphological, and TE properties of the resulting polymer/FWCNT composites are compared with those of composites composed of FWCNTs dispersed with conventional donor-only poly(3-hexylthiophene). The results reveal that the strong intermolecular interaction forces and high backbone planarity of the D-A polymers facilitate effective debundling of FWCNTs, which results in much smaller bundle sizes. Consequently, the D-A polymer/FWCNT composite films show superior electrical percolation and TE performances with improved power factors of up to 459 μW/mK². Finally, we demonstrate the feasibility of the D-A polymer/FWCNT composites for use in the fabrication of a flexible TE generator, which shows a maximum power output of 210 nW at a temperature gradient of 20 K.

Tuning the optoelectronic properties of oligothiophenes for solar cell applications by varying the number of cyano and fluoro substituents for solar cell applications: A theoretical study

Chemical modifications through substitution are observed to be effective in controlling the optoelectronic properties of various polymers for different applications. In this study, density functional theory–based calculations are employed to investigate the optoelectronic properties of several oligothiophenes based on poly(3-hexylthiophene-2,5-diyl) by varying the number of fluoro and cyano substituents attached. The resulting structures of the polymer derivatives are affected by the electrostatic interactions between the cyano or fluoro groups and the adjacent thiophene unit. Of the two, cyano substitution results in much lower frontier orbital energies for the same number of substituents. It was observed that a decrease in the highest occupied molecule orbital and lowest unoccupied molecular orbital energies correlates very strongly with the number of cyano and fluoro substituents. The effect of the cyano and fluoro groups on the frontier orbitals is also demonstrated and observed to correlate strongly with a lowering of the highest occupied molecule orbital and lowest unoccupied molecular orbital energies as the number of substituents is varied. The predicted solar cell characteristics reveal that most cyano and fluoro derivatives will have improved characteristics compared to unsubstituted poly(3-hexylthiophene-2,5-diyl). This theoretical study shows that by varying the number of electron-withdrawing substituents, the optoelectronic properties may be tuned for solar cell applications.

Computationally aided design of a high-performance organic semiconductor: the development of a universal crystal engineering core

Herein, we describe the design and synthesis of a suite of molecules based on a benzodithiophene "universal crystal engineering core". After computationally screening derivatives, a trialkylsilylethyne-based crystal engineering strategy was employed to tailor the crystal packing for use as the active material in an organic field-effect transistor. Electronic structure calculations were undertaken to reveal derivatives that exhibit exceptional potential for high-efficiency hole transport. The promising theoretical properties are reflected in the preliminary device results, with the computationally optimized material showing simple solution processing, enhanced stability, and a maximum hole mobility of 1.6 cm2 V-1 s-1.

Regulation of Molecular Packing and Blend Morphology by Finely Tuning Molecular Conformation for High-Performance Nonfullerene Polymer Solar Cells

The asymmetric thienobenzodithiophene (TBD) structure is first systematically compared with the benzo[1,2-b:4,5-b']dithiophene (BDT) and dithieno[2,3-d:2',3'-d']benzo[1,2-b:4,5-b']dithiophene (DTBDT) units in donor-acceptor (D-A) copolymers and applied as the central core in small molecule acceptors (SMAs). Specific polymers including PBDT-BZ, PTBD-BZ, and PDTBDT-BZ with different macromolecular conformations are synthesized and then matched with four elaborately designed acceptor-donor-acceptor (A-D-A) SMAs with structures comparable to their donor counterparts. The resulting polymer solar cell performance trends are dramatically different from each other and highly material-dependent, and the active layer morphology is largely governed by polymer conformation. Because of its more linear backbone, the PTBD-BZ film has higher crystallinity and more ordered and denser π-π stacking than those of the PBDT-BZ and PDTBDT-BZ films. Thus, PTBD-BZ shows excellent compatibility with and strong independence on the SMAs with varied structures, and PTBD-BZ-based cells deliver high power conversion efficiency (PCE) of 10-12.5%, whereas low PCE is obtained by cells based on PDTBDT-BZ because of its zigzag conformation. Overall, this study reveals control of molecular conformation as a useful approach to modulate the photovoltaic properties of conjugated polymers.

Influence of Backbone Regioregularity on High-Mobility Conjugated Polymers Based on Alkylated Dithienylacrylonitrile

We designed and synthesized two donor-acceptor type conjugated polymers, the regioirregular polymer RI-PDPP-CNTVT-6 and its regioregular counterpart RR-PDPP-CNTVT-6, based on diketopyrrolopyrrole (DPP) and alkylated dithienylacrylonitrile (CNTVT) units. Among them, the 2-decyltetradecyl side chain on the DPP acceptor unit and the hexyl side chain on the CNTVT donor unit were used to ensure enough solubility for them. The backbone regioregularity was used to tune electronic structures and carrier transport of the conjugated system. The two conjugated polymers were characterized for their thermal, photophysical, electrochemical, and solution-processable properties, thin-film microstructures, and morphologies. The top-gate bottom-contact configuration organic field-effect transistor (OFET) devices based on these two conjugated polymers showed excellent ambipolar performances. Remarkably, the regioirregular polymer RI-PDPP-CNTVT-6 exhibited higher charge-carrier mobilities than the regioregular counterpart polymer RR-PDPP-CNTVT-6 did, as their highest hole/electron mobilities (μ_hmax/μ_emax) were 1.48/1.27 and 0.48/0.052 cm² V^-1 s^-1, respectively. Moreover, the influence of backbone regioregularity on its thermal stability, electrochemical and photophysical properties, solution processability, and charge-carrier mobility was intensively studied. Our results afforded a promising pathway toward the development of excellent ambipolar OFETs with high performance, good solution processability, and thermal stability.

Synthesis of a Hominal Bis(difluoromethyl) Fragment

This paper describes the synthesis of a discrete unit of hominal bis(gem-CF₂). The controlled introduction of fluorine atoms is a powerful synthetic tool to introduce dipole moments with minimal impact to sterics. Poly(vinylidene difluoride) is a striking example of the influence of fluorine atoms, which impart ferroelectric behavior from the alignment of the dipole moments of CF₂ units; however, it is prepared via direct polymerization of vinylidene difluoride. Thus, a different synthetic pathway is required to produce synthons containing discrete numbers of CF₂ groups in a hominal relation to each other. We found out that, in the case of short chains, the consecutive deoxofluorination of sequentially introduced keto groups is inefficient, as it requires harsh conditions and decreasing yields at each step. To solve this problem, we combined the selective desulfurative fluorination of dithiolanes with pyridinium fluoride and the deoxofluorination of keto groups with morpholinosulfur trifluoride. This strategy is highly reproducible and scalable, allowing the synthesis of the hominal bis(gem-CF₂) fragment as a shelf-stable tosylate, which can be used to install discrete chains of hominal bis(gem-CF₂) on a variety of synthons and monomers.

A Quantitative Metric for the Design of Selective Supercritical CO2 Extraction of Lithium from Geothermal Brine

As demand grows for lithium, its recovery from geothermal brines provides an attractive alternative to slow mining. One promising extraction method uses crown ethers as extractants in supercritical carbon dioxide with cation exchangers to facilitate extraction from brine. Molecular dynamics modeling is used to understand the mechanism of binding between lithium (or sodium) and combinations of 14-crown-4 ethers and cation exchangers, and the predictive capability of computational modeling to test lithium selectivity is established for four combinations of crown ethers [methylene-14-crown-4 (M14C4) and a fluorinated 14-crown-4 (F14C4)] and cation exchangers [di(2-ethyl-hexyl)phosphoric acid (HDEHP) and tetraethylammonium perfluoro-1-octanesulfonate (TPFOS)]. Binding free energies (given in kcal mol^-1 ) of lithium and sodium, respectively, to crown ether-cation exchangers are 85 and 71 for M14C4-HDEHP, 90 and 71 for F14C4-HDEHP, 93 and 80 for M14C4-TPFOS, and 104 and 93 for F14C4-TPFOS. Good agreement is found between computational predictions and supercritical carbon dioxide extraction experiments at 60 °C and 250 bar. Binding free energy gives a suitable metric to describe extraction efficiency. Differences in the binding free energies of sodium and lithium to crown ethers determine the extraction selectivity. Fluorine groups are found to exert a positive influence to optimize extraction efficiency. Of the systems studied, F14C4 with TPFOS offers the most selective and efficient extraction system.

Fluoro-Modulated Molecular Geometry in Diketopyrrolopyrrole-Based Low-Bandgap Copolymers for Tuning the Photovoltaic Performance

Fluorination of conjugated polymers is an effective strategy to tune the energy levels for obtaining high power conversion efficiency (PCE) in organic solar cells. In this work, we have developed fluoro-modulated molecular geometries in diketopyrrolopyrrole based low-bandgap copolymers. In these polymers, planar conformation can be locked by intramolecular non-covalent interaction (intramolecular supramolecular interaction) between the sulfur atoms and the introduced F atoms (F···S interaction). By varying the fluorinated moieties, such a planarity can be disturbed and the molecular geometry is tuned. As a result, the polymer' properties can be modulated, including the ultraviolet-visible absorption spectrum to become broaden, charge mobility to be enhanced, open-circuit voltage (V _oc) and short-circuited current (J _sc) to be elevated, and thus photovoltaic performance to be improved. The photovoltaic device based on PCFB, one of the fluorinated terpolymers, exhibited a high PCE near 8.5% with simultaneously enhanced V _oc and J _sc relative to the non-fluorinated one (PCB).

Origin of the isotropic motion in crystalline molecular rotors with carbazole stators

Herein we report two crystalline molecular rotors 1 and 4 that show extremely narrow signals in deuterium solid-state NMR spectroscopy. Although this line shape is typically associated with fast-moving molecular components, our VT 2H NMR experiments, along with X-ray diffraction analyses and periodic DFT computations show that this spectroscopic feature can also be originated from low-frequency intramolecular rotations of the central phenylene with a cone angle of 54.7° that is attained by the cooperative motion of the entire structure that distorts the molecular axis to rotation. In contrast, two isomeric structures (2 and 3) do not show a noticeable intramolecular rotation, because their crystallographic arrays showed very restricting close contacts. Our findings clearly indicate that the multiple components and phase transitions in crystalline molecular machines can work in concert to achieve the desired motion.

High-Performance All-Polymer Solar Cells Enabled by an n-Type Polymer Based on a Fluorinated Imide-Functionalized Arene

A novel imide-functionalized arene, di(fluorothienyl)thienothiophene diimide (f-FBTI2), featuring a fused backbone functionalized with electron-withdrawing F atoms, is designed, and the synthetic challenges associated with highly electron-deficient fluorinated imide are overcome. The incorporation of f-FBTI2 into polymer affords a high-performance n-type semiconductor f-FBTI2-T, which shows a reduced bandgap and lower-lying lowest unoccupied molecular orbital (LUMO) energy level than the polymer analog without F or with F-functionalization on the donor moiety. These optoelectronic properties reflect the distinctive advantages of fluorination of electron-deficient acceptors, yielding "stronger acceptors," which are desirable for n-type polymers. When used as a polymer acceptor in all-polymer solar cells, an excellent power conversion efficiency of 8.1% is achieved without any solvent additive or thermal treatment, which is the highest value reported for all-polymer solar cells except well-studied naphthalene diimide and perylene diimide-based n-type polymers. In addition, the solar cells show an energy loss of 0.53 eV, the smallest value reported to date for all-polymer solar cells with efficiency > 8%. These results demonstrate that fluorination of imide-functionalized arenes offers an effective approach for developing new electron-deficient building blocks with improved optoelectronic properties, and the emergence of f-FBTI2 will change the scenario in terms of developing n-type polymers for high-performance all-polymer solar cells.

Cyano-Substituted Head-to-Head Polythiophenes: Enabling High-Performance n-Type Organic Thin-Film Transistors

Polythiophenes, built on the electron-rich thiophene unit, typically possess high-lying energy levels of the lowest unoccupied molecular orbitals (LUMOs) and show hole-transporting properties. In this study, we develop a series of n-type polythiophenes, P1-P3, based on head-to-head-linked 3,3'-dialkoxy-4,4'-dicyano-2,2'-bithiophene (BTCNOR) with distinct side chains. The BTCNOR unit shows not only highly planar backbone conformation enabled by the intramolecular noncovalent sulfur-oxygen interaction but also significantly suppressed LUMO level attributed to the cyano-substitution. Hence, all BTCNOR-based polymer semiconductors exhibit low-lying LUMO levels, which are ∼1.0 eV lower than that of regioregular poly(3-hexylthiophene) (rr-P3HT), a benchmark p-type polymer semiconductor. Consequently, all of the three polymers can enable unipolar n-type transport characteristics in organic thin-film transistors (OTFTs) with low off-currents ( I_offs) of 10^-10-10^-11 A and large current on/off ratios ( I_on/ I_offs) at the level of 10⁶. Among them, polymer P2 with a 2-ethylhexyl side chain offers the highest film ordering, leading to the best device performance with an excellent electron mobility (μ_e) of 0.31 cm² V^-1 s^-1 in off-center spin-cast OTFTs. To the best of our knowledge, this is the first report of n-type polythiophenes with electron mobility comparable to the hole mobility of the benchmark p-type rr-P3HT and approaching the electron mobility of the most-studied n-type polymer, poly(naphthalene diimide- alt-bithiophene) (i.e., N2200). The change of charge carrier polarity from p-type (rr-P3HT) to n-type (P2) with comparable mobility demonstrates the obvious effectiveness of our structural modification. Adoption of n-hexadecyl (P1) and 2-butyloctyl (P3) side chains leads to reduced film ordering and results in 1-2 orders of magnitude lower μ_es, showing the critical role of side chains in optimizing device performance. This study demonstrates the unique structural features of head-to-head linkage containing BTCNOR for constructing high-performance n-type polymers, i.e., the alkoxy chain for backbone conformation locking and providing polymer solubility as well as the strong electron-withdrawing cyano group for lowering LUMO levels and enabling n-type performance. The design strategy of BTCNOR-based polymers provides useful guidelines for developing n-type polythiophenes.

Influence of Backbone Chlorination on the Electronic Properties of Diketopyrrolopyrrole (DPP)-Based Dimers

Chlorination of π-conjugated backbones is garnering great interest because of fine-tuning electronic properties of conjugated materials for organic devices. Herein we report a synthesis of thiophene-based diketopyrrolopyrrole (DPP) dimers and their chlorinated counterparts by introducing a chlorine atom in the outer thiophene ring to investigate the influence of the chlorination on charge transport. The backbone chlorination lowers both the HOMO and the LUMO of the dimers and leads to a blue-shift of maximum absorption in compared to unsubstituted counterparts. X-ray analysis reveals that the chlorine atom prompts the outer thiophene ring out of the planarity of the backbone with a relatively large torsional angle. The chlorinated dimers exhibit slipped one-dimensional packing decorated with multiple intermolecular interactions, because of a combination of a negative inductive effect and a positive mesomeric effect of the halogen atom, which might facilitate charge transport within the oligomeric backbones. The mobility in the single-crystal OFET devices of the chlorinated dimers is up to 1.5 cm²  V^-1  s^-1 , which is two times higher than that of the non-chlorinated DPP dimers. Our results indicate that the chlorine atom plays a key role in directing non-covalent interactions to lock the slipped stacks, enabling electronic coupling between adjacent molecules for efficient charge transport. In addition, our results also demonstrate that these DPP dimers with straight n-octyl chains exhibit higher mobilities than the dimers with branched 2-ethylhexyl chains.

A 3-Fluoro-4-hexylthiophene-Based Wide Bandgap Donor Polymer for 10.9% Efficiency Eco-Friendly Nonfullerene Organic Solar Cells

Nonfullerene organic solar cells (NFOSCs) are attracting increasing academic and industrial interest due to their potential uses for flexible and lightweight products using low-cost roll-to-roll technology. In this work, two wide bandgap (WBG) polymers, namely P(fTh-BDT)-C6 and P(fTh-2DBDT)-C6, are designed and synthesized using benzodithiophene (BDT) derivatives. Good oxidation stability and high solubility are achieved by simultaneously introducing fluorine and alkyl chains to a single thiophene (Th) unit. Solid P(fTh-2DBDT)-C6 films present WBG optical absorption, suitable frontier orbital levels, and strong π-π stacking effects. In addition, P(fTh-2DBDT)-C6 exhibits good solubility in both halogenated and nonhalogenated solvents, suggesting its suitability as donor polymer for NFOSCs. The P(fTh-2DBDT)-C6:3,9-bis(2-methylene-(3-(1,1-dicyanomethylene)-indanone))-5,5,11,11-tetrakis(5-hexylthienyl)-dithieno[2,3-d:2',3'-d']-s-indaceno[1,2-b:5,6-b']dithiophene (ITIC-Th) based device processed using chlorobenzene/1,8-diiodooctane (CB/DIO) exhibits a remarkably high power conversion efficiency (PCE) of 11.1%. Moreover, P(fTh-2DBDT)-C6:ITIC-Th reaches a high PCE of 10.9% when processed using eco-friendly solvents, such as o-xylene/diphenyl ether (DPE). The cell processed using CB/DIO maintains 100% efficiency after 1272 h, while that processed using o-xylene/DPE presents a 101% increase in efficiency after 768 h and excellent long-term stability. The results of this study demonstrate that simultaneous fluorination and alkylation are effective methods for designing donor polymers appropriate for high-performance NFOSCs.