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All sourcesNASA NTRSDOE OSTI
DOE OSTI2026

Tunable Nanoscale Structure via Divalent Ion Identity in Charged-Neutral Polymer Blends

Charged-neutral polymer blends, wherein an ioncontaining polymer is blended with a neutral polymer, are potential candidates for battery electrolytes due to their improved ion transport properties and electrochemical stability. Though electrostatic interactions in charged polymer blends can theoretically stabilize ordered nanostructures analogous to those observed in neutral block copolymers, direct experimental evidence remains limited. Here, we investigate the effects of divalent cation identity on the nanoscale morphology of charged-neutral polymer blends composed of poly(ethylene oxide) (PEO) and Mg 2+ or Ca 2+ ioncontaining polymers, poly[3-(methylacryloxy)propylsulfonyl-1-(trifluoromethanesulfonylimide)] (P(Mg(MTFSI) 2 ) or P(Ca- (MTFSI) 2 ). By tuning the size of the divalent counterion, we are able to precisely tune the ion solvation between the free cation and PEO, which acts as a solvent in this system. Differential scanning calorimetry (DSC) and small-angle X-ray scattering (SAXS) measurements reveal that Mg 2+ and Ca 2+ ions induce distinct structural behavior. In both systems, the blends become more miscible as the concentration of ion-containing polymer is increased indicated by increased suppression of PEO crystallinity. At the highest concentrations of P(Mg(MTFSI) 2 ), the blends undergo microphase separation and generate nanostructures with shortranged ordering. In contrast, calcium ions, which are more readily solvated by PEO, produce more homogeneous blends characterized by a single glass-transition temperature and featureless SAXS data. The results demonstrate the novel experimental confirmation that charged-neutral polymer blends can undergo microphase separation and show that counterion identity can be exploited as a design parameter to control nanoscale morphology.

Ions↗
DOE OSTI2020

Impact of particle arrays on phase separation composition patterns

We examine the symmetry-breaking effect of fixed constellations of particles on the surface-directed spinodal decomposition of binary blends in the presence of particles whose surfaces have a preferential affinity for one of the components. Our phase-field simulations indicate that the phase separation morphology in the presence of particle arrays can be tuned to have a continuous, droplet, lamellar, or hybrid morphology depending on the interparticle spacing, blend composition, and time. In particular, when the interparticle spacing is large compared to the spinodal wavelength, a transient target pattern composed of alternate rings of preferred and non-preferred phases emerges at early times, tending to adopt the symmetry of the particle configuration. We reveal that such target patterns stabilize for certain characteristic length, time, and composition scales characteristic of the pure phase-separating mixture. To illustrate the general range of phenomena exhibited by mixture-particle systems, we simulate the effects of single-particle, multi-particle, and cluster–particle systems having multiple geometrical configurations of the particle characteristic of pattern substrates on phase separation. Our simulations show that tailoring the particle configuration, or substrate pattern configuration, a relative fluid-particle composition should allow the desirable control of the phase separation morphology as in block copolymer materials, but where the scales accessible to this approach of organizing phase-separated fluids usually are significantly larger. Limited experiments confirm the trends observed in our simulations, which should provide some guidance in engineering patterned blend and other mixtures of technological interest.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2022

The Importance of Nonequilibrium to Equilibrium Transition Pathways for the Efficiency and Stability of Organic Solar Cells

Controlled morphology of solution-processed thin films have realized impressive achievements for non-fullerene acceptor (NFA)–based organic solar cells (OSCs). Given the large set of donor–acceptor pairs, employing various processing conditions to realize optimal morphology for high efficiency and stable OSCs is a strenuous task. Therefore, comprehensive correlations between processing conditions and morphology evolution pathways have to be developed for efficient performance and stability of devices. Within the framework of the blend system, crystallization transitions of NFA molecules are tracked utilizing the first heating scan of differential scanning calorimeter (DSC) measurement correlating with respective morphology evolution of blend films. Real-time dynamics measurements and morphology characterizations are combined to provide optimal morphology transition pathways as NFA molecules are shown to be released from the mixed phase to form balanced ordered packing with variant processing conditions. Polymer:NFA films are fabricated using blade coating incorporating solvent additive or thermal annealing as processing conditions as a correlation is formulated between performance and stability of solar cells with morphology transition pathways. In conclusion, this work demonstrates the significance of processing condition-controlled transition pathways for the realization of optimal morphology leading to superior OSC devices.

14 SOLAR ENERGY↗
DOE OSTI2026

Mechanistic origin of solvent-dependent thermal stability in sodiated Sn anodes for sodium-ion batteries

Understanding the thermal stability of high-energy density alloy anodes is critical for the safe deployment of sodium-ion batteries (SIBs). Here, accelerating rate calorimetry (ARC), post-mortem characterizations, and density functional theory (DFT) calculations are combined to understand the thermal reactivity of fully sodiated Sn, Sn-hard carbon (HC) blends, and HC anodes in carbonate- and ether-based electrolytes. ARC measurements show that propylene carbonate (PC) causes earlier self-heating rate (SHR) onset and higher reactivity than tetraethylene glycol dimethyl ether (TEGDME), indicating inferior thermal stability. Sodiated Sn exhibits better thermal stability than sodiated HC, while Sn-HC blends show intermediate behavior that improves with increasing Sn content. Post-ARC analyses reveal desodiation of Na15Sn4 to metallic Sn with particle coalescence, whereas Sn-HC blends and HC retain finer morphologies. PC promotes Sn oxidation to SnO, while TEGDME suppresses oxide formation; NaPF6-containing electrolytes additionally form NaF. DFT calculations show that PC adsorption lowers Na extraction energy and enhances interfacial electronic interactions, facilitating Na release and reductive decomposition. These results establish a direct correlation between solvent-dependent reaction pathways and thermal stability in SIB alloy anodes.

Accelerating rate calorimetry↗
DOE OSTI2022

Correlating Electronic Structure and Device Physics with Mixing Region Morphology in High-Efficiency Organic Solar Cells

The donor/acceptor interaction in non-fullerene organic photovoltaics leads to the mixing domain that dictates the morphology and electronic structure of the blended thin film. Initiative effort is paid to understand how these domain properties affect the device performances on high-efficiency PM6:Y6 blends. Different fullerenes acceptors are used to manipulate the feature of mixing domain. It is seen that a tight packing in the mixing region is critical, which could effectively enhance the hole transfer and lead to the enlarged and narrow electron density of state (DOS). As a result, short-circuit current (J SC ) and fill factor (FF) are improved. The distribution of DOS and energy levels strongly influences open-circuit voltage (V OC ). The raised filling state of electron Fermi level is seen to be key in determining device V OC . Energy disorder is found to be a key factor to energy loss, which is highly correlated with the intermolecular distance in the mixing region. A 17.53% efficiency is obtained for optimized ternary devices, which is the highest value for similar systems. The current results indicate that a delicate optimization of the mixing domain property is an effective route to improve the V OC , J SC , and FF simultaneously, which provides new guidelines for morphology control toward high-performance organic solar cells.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Impact of Ionic Liquid on Lithium Ion Battery with a Solid Poly(Ionic Liquid) Pentablock Terpolymer as Electrolyte and Separator

In this work, a ternary blend solid polymer electrolyte (SPE) consisting of a poly(ionic liquid) (PIL) multiblock polymer, lithium salt, and ionic liquid (IL) was investigated with the goal of understanding the influence of IL concentration on ion transport mechanisms and electrochemical stability. The physical, transport, mechanical, morphological, and electrochemical properties of the ternary blend SPE were systematically investigated as a function of IL concentration (r = [IL]/[PIL] mole ratio between 0.1 and 0.7). The results indicate that with increasing IL concentration, the continuous conductive domain increases along with the polymer chain segmental mobility, as well as facilitate ionic conductivity, while the mechanical modulus exhibits a percolation threshold (from 52.17 MPa to 0.55 MPa at r = 0.2 to 0.3). Surprisingly, at higher IL concentrations, there is a reduction in the lithium cation mobility (i.e., 9.3 × 10-12 m2 s-1 versus 3.8 × 10-12 m2 s-1 for r = 0.2 versus r = 0.5, respectively) as evidenced by pulsed-field gradient nuclear magnetic resonance (PFG-NMR), which coincides with an increased overpotential (i.e., 50 mV versus 150 mV for r = 0.2 versus r = 0.5, respectively) evidenced by lithium metal stripping and plating. This work provides valuable insights into the impact of IL on lithium ion conducting PIL block polymers, which may enable the design of new SPEs with both high ionic conductivity and improved stability for the future lithium ion batteries.

Chen, Tzu-Ling↗
DOE OSTI2021

Phase segregation mechanisms of small molecule-polymer blends unraveled by varying polymer chain architecture

As phase separation between the small-molecule semiconductor and the polymer binder is the key enabler of blend-based organic field-effect transistors (OFETs) fabricated by low-cost solution processing, it is crucial to understand the underlying phase separation mechanisms that determine the phase morphology, which significantly impacts device performance. Beyond the parameter space investigated in previous work, here we investigate the formation of blends by varying the branch architecture of the polymer binder and by shortening the solvent dry time using ultrasonic spray casting. The phase morphologies of the resulting blend films have been thoroughly characterized with a variety of techniques in three dimensions over multiple length scales, including AFM, energy-filtered transmission electron microscope, and neutron reflectivity, and have been correlated with electrical transport performance. From the results, we have inferred that the phase morphology is kinetically determined, limited by the inherent slow movement of polymer macromolecules. The kinetic picture, supported by molecular dynamics modeling, not only consistently explains our observations but also resolves inconsistencies in previous works. The achieved mechanistic understanding will guide further optimization of blend-based organic electronics, such as OFETs and organic photovoltaics.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Efficient, Thermally Stable, and Mechanically Robust All-Polymer Solar Cells Consisting of the Same Benzodithiophene Unit-Based Polymer Acceptor and Donor with High Molecular Compatibility

All-polymer solar cells (all-PSCs) are a highly attractive class of photovoltaics for wearable and portable electronics due to their excellent morphological and mechanical stabilities. Recently, new types of polymer acceptors (P A s) consisting of non-fullerene small molecule acceptors (NFSMAs) with strong light absorption have been proposed to enhance the power conversion efficiency (PCE) of all-PSCs. However, polymerization of NFSMAs often reduces entropy of mixing in PSC blends and prevents the formation of intermixed blend domains required for efficient charge generation and morphological stability. One approach to increase compatibility in these systems is to design P A s that contain the same building blocks as their polymer donor (P D ) counterparts. Here, a series of NFSMA-based P A s [P(BDT2BOY5-X), (X = H, F, Cl)] are reported, by copolymerizing NFSMA (Y5-2BO) with benzodithiophene (BDT), a common donating unit in high-performance P D s such as PBDB-T. All-PSC blends composed of PBDB-T PD and P(BDT2BOY5-X) P A show enhanced molecular compatibility, resulting in excellent morphological and electronic properties. Specifically, PBDB-T:P(BDT2BOY5-Cl) all-PSC has a PCE of 11.12%, which is significantly higher than previous PBDB-T:Y5-2BO (7.02%) and PBDB-T:P(NDI2OD-T2) (6.00%) PSCs. Additionally, the increased compatibility of these all-PSCs greatly improves their thermal stability and mechanical robustness. For example, the crack onset strain (COS) and toughness of the PBDB-T:P(BDT2BOY5-Cl) blend are 15.9% and 3.24 MJ m -3 , respectively, in comparison to the PBDB-T:Y5-2BO blends at 2.21% and 0.32 MJ m -3 .

14 SOLAR ENERGY↗
DOE OSTI2022

Unique W-Shape Y6 isomer as effective solid additive for High-Performance PM6:Y6 polymer solar cells

The current top-performing polymer solar cell (PSC) systems are mostly based on PM6:Y6 host blend. To date, numerous materials have been explored as the third component for these systems to form ternary blends or as additives. Vitrification agents are a group of additives proved to be useful in affecting the morphology of organic semiconductors. Here to design a suitable vitrification agent for non-fullerene electron acceptor Y6, an isomer strategy was explored where the thienothiophene wings of the Y6 molecule were inversed to form a W-shaped Y6 isomer of i-Y6. It was found that i-Y6 crystallized poorly with a different packing style than Y6 and could blend well in amorphous phase of Y6. These properties enabled i-Y6 to finely tune the morphology of PM6:Y6 blend at low additive dosages. The power conversion efficiency (PCE) of PM6:Y6 based PSC was raised from 16.827% to 17.433% at a dosage of Y6:i-Y6 ratio of 24:1. This work demonstrated isomerization as a viable strategy for developing solid additives for high performance PSC blends and vitrification agents as effective additives for tuning morphology and improving performances of PSCs.

36 MATERIALS SCIENCE↗
DOE OSTI2025

The Influence of Charge Correlation and Ion Solvation on the Phase Behavior of Single-Ion Conducting Polymer Blend Electrolytes Using SAXS/SANS

Single-ion conducting polymer blends (SICPBs) have demonstrated exceptional electrochemical performance as solid-state battery electrolytes; however, their nanoscale morphology and thermodynamic behavior remain unexplored. In this work, we investigate blends composed of deuterated poly(ethylene oxide) and poly[lithium sulfonyl(trifluoromethane sulfonyl)imide methacrylate], dPEO/P(LiMTFSI), and report the first experimental study of the nanostructures of charge-neutral polymer blends using small-angle neutron scattering (SANS) and small-angle X-ray scattering (SAXS). Despite the macroscopic miscibility indicated by a single glass-transition temperature, SANS and SAXS results reveal disordered, charge-correlated nanostructures that are strongly influenced by blend composition and temperature. At low concentrations of charge polymer, the scattering is dominated by concentration fluctuations, and the random phase approximation is applied to extract values of the Flory–Huggins interaction parameter, χ SC . At higher charged polymer content, concentration fluctuations are suppressed, and a correlation model is used to characterize the nanostructures of the charge correlations. We find that the structures of the charge correlations are highly dependent on blend composition─consistent with predictions from Sing’s self-consistent field theory-liquid state models. Understanding these features is essential for uncovering the ion transport mechanism that leads to improved electrochemical performance previously reported in SICPB systems.

25 ENERGY STORAGE↗
DOE OSTI2025

Dynamic disulfide bond networks enable self-healable and mechanically resilient intrinsically stretchable organic solar cells

A dynamic disulfide network introduced into donor/acceptor blends enables room-temperature self-healing and mechanical resilience in intrinsically stretchable organic solar cells, achieving performance recovery after high mechanical strain. The development of intrinsically stretchable organic solar cells (IS-OSCs) faces significant challenges in balancing mechanical durability and optoelectronic performance. Conventional π-conjugated polymer-based donor/acceptor blend films often exhibit limited stretchability and irreversible performance degradation under mechanical strain. To address these limitations, we propose a novel self-healable donor/acceptor blended film with a dual-network morphology, achieved by incorporating a dynamic disulfide bond-based crosslinked network into the bulk-heterojunction film. The resulting thin films demonstrate a power conversion efficiency (PCE) of 16.39% in rigid OSC devices and a fracture strain of 15.6%. Remarkably, the IS-OSCs retain 80% of their initial PCE under 30% strain and exhibit performance recovery after multiple stretch-release cycles at 40% strain through a room-temperature self-healing process. This work provides a proof-of-concept for highly stretchable and durable IS-OSCs, offering valuable insights for advancing the field of wearable energy systems, adaptive solar textiles, and sustainable electronics.

Yang, Wenyu↗
DOE OSTI2024

Crossbreeding Effect of Chalcogenation and Iodination on Benzene Additives Enables Optimized Morphology and 19.68% Efficiency of Organic Solar Cells

Volatile solid additives have attracted increasing attention in optimizing the morphology and improving the performance of currently dominated non-fullerene acceptor-based organic solar cells (OSCs). However, the underlying principles governing the rational design of volatile solid additives remain elusive. Herein, a series of efficient volatile solid additives are successfully developed by the crossbreeding effect of chalcogenation and iodination for optimizing the morphology and improving the photovoltaic performances of OSCs. Five benzene derivatives of 1,4-dimethoxybenzene (DOB), 1-iodo-4-methoxybenzene (OIB), 1-iodo-4-methylthiobenzene (SIB), 1,4-dimethylthiobenzene (DSB) and 1,4-diiodobenzene (DIB) are systematically studied, where the widely used DIB is used as the reference. The effect of chalcogenation and iodination on the overall property is comprehensively investigated, which indicates that the versatile functional groups provided various types of noncovalent interactions with the host materials for modulating the morphology. Among them, SIB with the combination of sulphuration and iodination enabled more appropriate interactions with the host blend, giving rise to a highly ordered molecular packing and more favorable morphology. As a result, the binary OSCs based on PM6:L8-BO and PBTz-F:L8-BO as well as the ternary OSCs based on PBTz-F:PM6:L8-BO achieved impressive high PCEs of 18.87%, 18.81% and 19.68%, respectively, which are among the highest values for OSCs.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Compressibility Studies of Copper Selenides Obtained by Cation Exchange Reaction Revealing the New CsCl Phase

In this study, we conducted a high-pressure investigation of Cu 2-x Se nanostructures with pyramid- and plate-like morphologies, created through cation exchange from zinc-blende CdSe nanocrystals and wurtzite CdSe nanoplatelets respectively. Using a diamond anvil cell setup at the APS synchrotron, we observed the phase transitions in the Cu 2-x Se nanostructures up to 40 GPa, identifying a novel CsCl-type lattice with Pm-3m symmetry above 4 GPa. This CsCl-type structure, previously unreported in copper selenides, was partially retained after decompression. Our results indicate that the initial crystalline structure of CdSe does not affect the stability of Cu 2-x Se nanostructures formed via cation exchange. Both morphologies of Cu 2-x Se sintered under compression, potentially contributing to the stabilization of the high-pressure phase through interfacial defects. These findings are significant for discovering new phases with potential applications in future technologies.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

Bridging the thermodynamics and kinetics of temperature-induced morphology evolution in polymer/fullerene organic solar cell bulk heterojunction

The performance of organic solar cells (OSC) critically depends on the morphology of the active layer. After deposition, the active layer is in a metastable state and prone to changes that lead to cell degradation. Here, a high efficiency fullerene:polymer blend is used as a model system to follow the temperature-induced morphology evolution through a series of thermal annealing treatments. Electron microscopy analysis of the nano-scale phase evolution during the early stages of thermal annealing revealed that spinodal decomposition, i.e. spontaneous phase separation with no nucleation stage, is possibly responsible for the formation of a fine scale bicontinuous structure. In the later evolution stages, large polycrystalline fullerene aggregates are formed. Optical microscopy and scattering revealed that aggregate-growth follows the Johnson–Mehl–Avrami–Kolmogorov equation indicating a heterogeneous transformation process, i.e., through nucleation and growth. These two mechanisms, spinodal decomposition vs. nucleation and growth, are mutually exclusive and their co-existence is surprising. This unexpected observation is resolved by introducing a metastable monotectic phase diagram and showing that the morphology evolution goes through two distinct and consecutive transformation processes where spinodal decomposition of the amorphous donor:acceptor blend is followed by nucleation and growth of crystalline acceptor aggregates. Lastly, this unified thermodynamic and kinetic mechanism allows us to correlate the morphology evolution with OSC degradation during thermal annealing.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Versatile Sequential Casting Processing for Highly Efficient and Stable Binary Organic Photovoltaics

Forming an ideal bulk heterojunction (BHJ) morphology is a critical issue governing the photon to electron process in organic solar cells (OSCs). Complementary to the widely-used blend casting (BC) method for BHJ construction, sequential casting (SC) can also enable similar or even better morphology and device performance for OSCs. Here, BC and SC methods on three representative donor:acceptor (D:A) blends are utilized, that is, PM6:PC 71 BM, PM6:IT-4F and PM6:L8-BO. Higher power conversion efficiencies (PCEs) in all cases by taking advantage of beneficial morphology from SC processing are achieved, and a champion PCE of 18.86% (certified as 18.44%) based on the PM6:L8-BO blend is reached, representing the record value among binary OSCs. The observations on phase separation and vertical distribution inspire the proposal of the swelling–intercalation phase-separation model to interpret the morphology evolution during SC processing. Further, the vertical phase segregation is found to deliver an improvement of device performance via affecting the charge transport and collection processes, as evidenced by the D:A-ratio-dependent photovoltaic properties. Besides, OSCs based on SC processing show advantages on device photostability and upscale fabrication. Finally, this work demonstrates the versatility and efficacy of the SC method for BHJ-based OSCs.

14 SOLAR ENERGY↗
DOE OSTI2020

Charge generation mechanism tuned via film morphology in small molecule bulk-heterojunction photovoltaic materials

Small organic molecules have emerged as promising component materials for organic photovoltaic devices. Compared to most conjugated polymers for the same application, small molecules have unique morphologies that promote electronic processes relevant to organic solar cell (OSC) function that can be significantly different from those of conjugated polymeric materials. Here we investigate constituent loading-dependent effects on OSC morphology and function using the classical fullerene acceptor, PC 61 BM, in a heterojunction blend with the small molecule donor, NDT (thiophene-capped diketopyrrolopyrrole naphthodithiophene). The evolution of active layer morphology as well as exciton speciation and dynamics as a function of the PC 61 BM content are examined in combined structural studies using GIWAXS and spectroscopic studies using transient absorption spectroscopy. We observe evidence for three types of coexisting excitons and details of the interplay between them determines the yield of charge separated states that afford sustained device efficiency.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

Revealing the Surface Structure of CdSe Nanocrystals by Dynamic Nuclear Polarization-Enhanced 77 Se and 113 Cd Solid-State NMR Spectroscopy

Dynamic nuclear polarization (DNP) solid-state NMR (SSNMR) spectroscopy was used to obtain detailed surface structures of zinc blende CdSe nanocrystals (NCs) with plate or spheroidal morphologies which are capped by carboxylic acid ligands. 1D 113 Cd and 77 Se cross-polarization magic angle spinning (CPMAS) NMR spectra revealed distinct signals from Cd and Se atoms on the surface of the NCs, and those residing in bulk-like environments, below the surface. 113 Cd cross-polarization magic-angle-turning (CP-MAT) experiments identified CdSe 3 O, CdSe 2 O 2 , and CdSeO 3 Cd coordination environments on the surface of the NCs, where the oxygen atoms are presumably from coordinated carboxylate ligands. The sensitivity gain from DNP enabled natural isotopic abundance 2D homonuclear 113 Cd– 113 Cd and 77 Se– 77 Se and heteronuclear 113 Cd– 77 Se scalar correlation solid-state NMR experiments which revealed the connectivity of the Cd and Se atoms. Importantly, 77 Se{ 113 Cd} scalar heteronuclear multiple quantum coherence ( J -HMQC) experiments were used to selectively measure one-bond 77 Se– 113 Cd scalar coupling constants ( 1 J ( 77 Se, 113 Cd)). With knowledge of 1 J ( 77 Se, 113 Cd), heteronuclear 77 Se{ 113 Cd} spin echo ( J -resolved) NMR experiments were used to determine the number of Cd atoms bonded to Se atoms and vice versa. Furthermore, the J -resolved experiments directly confirmed that major Cd and Se surface species have CdSe 2 O 2 and SeCd 4 stoichiometries, respectively. Considering the crystal structure of zinc blende CdSe and the similarity of the solid-state NMR data for the platelets and spheroids, we conclude that the surface of the spheroidal CdSe NCs is primarily composed of {100} facets. The methods outlined here will generally be applicable to obtain detailed surface structures of various main group semiconductor nanoparticles.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

A Difluoro‐Monobromo End Group Enables High‐Performance Polymer Acceptor and Efficient All‐Polymer Solar Cells Processable with Green Solvent under Ambient Condition

Abstract In this paper, a difluoro‐monobromo end group is designed and synthesized, which is then used to construct a novel polymer acceptor (named PY2F‐T) yielding high‐performance all‐polymer solar cells with 15.22% efficiency. The fluorination strategy can increase the intramolecular charge transfer and interchain packing of the previous PY‐T based acceptor, and significantly improve photon harvesting and charge mobility of the resulting polymer acceptor. In addition, detailed morphology investigations reveal that the PY2F‐T‐based blend shows smaller domain spacing and higher domain purity, which significantly suppress charge recombination as supported by time‐resolved techniques. These polymer properties enable simultaneously enhanced J SC and FF of the PY2F‐T‐based devices, eventually delivering device efficiencies of over 15%, significantly outperforming that of the devices based on the non‐fluorinated PY‐T polymer (13%). More importantly, the PY2F‐T‐based active layers can be processed under ambient conditions and still achieve a 14.37% efficiency. They can also be processed using non‐halogenated solvent o ‐xylene (no additive) and yield a decent performance of 13.05%. This work demonstrates the success of the fluorination strategy in the design of high‐performance polymer acceptors, which provide guidelines for developing new all‐PSCs with better efficiencies and stabilities for commercial applications.

Yu, Han↗