以昇陳

A new spiro derivative, SPS‐4F, is designed and synthesized as a nonfullerene electron transport material in perovskite solar cells. An efficiency of 20.31% and high device stability are simultaneously achieved in the resultant devices. This work opens up opportunities to obtain a new family of spiro‐based electron transport materials and paves a way for realizing high‐performance devices with low cost.

Abstract

Electron transport materials (ETMs) play a significant role in perovskite solar cells (PSCs). However, conventional solution processable organic ETMs are mainly restricted to fullerene derivatives and it is challenging to obtain nonfullerene ETMs with satisfactory properties. In this work, a new organic semiconductor SPS‐4F is synthesized by utilizing the classical spiro[fluorine‐9′9‐thioxanthene] unit to construct a π‐extended core. Although spiro is normally used in hole transport materials, the new spiro derivative SPS‐4F is successfully used as an ETM in inverted PSCs with power conversion efficiency over 20%. In addition, SPS‐4F can strongly coordinate with MAPbI₃ perovskite and lead to efficient surface trap passivation. The resultant PSCs exhibit excellent stability in air because of the hydrophobic property of SPS‐4F. This work opens up opportunities to obtain a new family of ETMs based on spiro and paves a way to the fabrication of high‐performance PSCs with low cost.

The popular poly(3,4‐ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) hole transporter layer in perovskite light‐emitting diodes will cause some loss of photons and result in limited device performance. Herein, to overcome this problem, an ultrathin PEDOT:PSS is prepared, and performance is successfully improved in 3D, quasi‐3D, and quasi‐2D perovskites.

Abstract

Recently, metal halide perovskite light‐emitting diodes (Pero‐LEDs) have achieved significant improvement in device performance, especially for external quantum efficiency (EQE). And EQE is mostly determined by internal quantum efficiency of the emitting material, charge injection balancing factor (η_c), and light extraction efficiency (LEE) of the device. Herein, an ultrathin poly(3,4‐ethylenedioxythiophene):poly(styrene sulfonate) (UT‐PEDOT:PSS) hole transporter layer is prepared by a water stripping method, and the UT‐PEDOT:PSS can enhance η_c and LEE simultaneously in Pero‐LEDs, mostly due to the improved carrier mobility, more matched energy level alignment, and reduced photon loss. More importantly, the performance enhancement from UT‐PEDOT:PSS is quite universal and applicable in different kinds of Pero‐LEDs. As a result, the EQEs of Pero‐LEDs based on 3D, quasi‐3D, and quasi‐2D perovskites obtain enhancements of 42%, 87%, and 111%, and the corresponding maximum EQE reaches 17.6%, 15.0%, and 6.8%, respectively.

Herein, studies about the degradation mechanism and stability improving strategies of organic solar cells (OSCs) in the past few years are reviewed. The current inconsistency in the stability measurement and the importance of the International Summit on Organic Photovoltaic Stability standards are discussed, and outlooks and research directions in the stability of OSCs in the near future are proposed.

Abstract

The organic solar cell (OSC) is a promising emerging low‐cost thin film photovoltaics technology. The power conversion efficiency (PCE) of OSCs has overpassed 16% for single junction and 17% for organic–organic tandem solar cells with the development of low bandgap organic materials synthesis and device processing technology. The main barrier of commercial use of OSCs is the poor stability of devices. Herein, the factors limiting the stability of OSCs are summarized. The limiting stability factors are oxygen, water, irradiation, heating, metastable morphology, diffusion of electrodes and buffer layers materials, and mechanical stress. The recent progress in strategies to increase the stability of OSCs is surveyed, such as material design, device engineering of active layers, employing inverted geometry, optimizing buffer layers, using stable electrodes and encapsulation materials. The International Summit on Organic Photovoltaic Stability guidelines are also discussed. The potential research strategies to achieve the required device stability and efficiency are highlighted, rendering possible pathways to facilitate the viable commercialization of OSCs.

In article number https://doi.org/10.1002/advs.2019037841903784, Feng He and co‐workers report a bromination strategy for efficient non‐fullerene acceptors with solar conversion efficiency over 16%. The single crystal structures reveal that these brominated acceptors exhibit good planarity in terms of single molecular configuration. The multiple inter‐locked Br‐S and Br‐π interactions allow them to form 3D interpenetrating networks with more charge transfer junctions.

Asymmetric electron acceptors, by combining halogenated indandione and 3‐dicyanomethylene‐1‐indanone as two different conjugated terminals, are designed and synthesized. Such design enables reduced energy loss and boosts charge separation, thus leading to 16.37% binary organic photovoltaics (OPVs) and 17.43% ternary OPVs, which are among the best efficiencies for single‐junction OPVs.

Abstract

Low energy loss and efficient charge separation under small driving forces are the prerequisites for realizing high power conversion efficiency (PCE) in organic photovoltaics (OPVs). Here, a new molecular design of nonfullerene acceptors (NFAs) is proposed to address above two issues simultaneously by introducing asymmetric terminals. Two NFAs, BTP‐S1 and BTP‐S2, are constructed by introducing halogenated indandione (A₁) and 3‐dicyanomethylene‐1‐indanone (A₂) as two different conjugated terminals on the central fused core (D), wherein they share the same backbone as well‐known NFA Y6, but at different terminals. Such asymmetric NFAs with A₁‐D‐A₂ structure exhibit superior photovoltaic properties when blended with polymer donor PM6. Energy loss analysis reveals that asymmetric molecule BTP‐S2 with six chlorine atoms attached at the terminals enables the corresponding devices to give an outstanding electroluminescence quantum efficiency of 2.3 × 10⁻²%, one order of magnitude higher than devices based on symmetric Y6 (4.4 × 10⁻³%), thus significantly lowering the nonradiative loss and energy loss of the corresponding devices. Besides, asymmetric BTP‐S1 and BTP‐S2 with multiple halogen atoms at the terminals exhibit fast hole transfer to the donor PM6. As a result, OPVs based on the PM6:BTP‐S2 blend realize a PCE of 16.37%, higher than that (15.79%) of PM6:Y6‐based OPVs. A further optimization of the ternary blend (PM6:Y6:BTP‐S2) results in a best PCE of 17.43%, which is among the highest efficiencies for single‐junction OPVs. This work provides an effective approach to simultaneously lower the energy loss and promote the charge separation of OPVs by molecular design strategy.

Fluorinated, π‐extended end groups imbue indacenodithienothiophene‐based acceptors (ITN‐F4 and ITzN‐F4) with higher power conversion efficiency, stronger π–π electronic coupling, lower reorganization energies, and highly connected crystal structures. Femtosecond absorption spectroscopy reveals ultrafast hole transfer (<300 fs) in blends with donor polymer poly{[4,8‐bis[5‐(2‐ethylhexyl)‐4‐fluoro‐2‐thienyl]benzo[1,2‐b :4,5‐b ′]‐dithiophene‐2,6‐diyl]‐alt‐[2,5‐thiophenediyl[5,7‐bis(2‐ethylhexyl)‐4,8‐dioxo‐4H ,8H‐benzo[1,2‐c :4,5‐c ′]dithiophene‐1,3‐diyl]]} (PBDB‐TF), despite excimer formation.

Abstract

The synthesis and characterization of new semiconducting materials is essential for developing high‐efficiency organic solar cells. Here, the synthesis, physiochemical properties, thin film morphology, and photovoltaic response of ITN‐F4 and ITzN‐F4, the first indacenodithienothiophene nonfullerene acceptors that combine π‐extension and fluorination, are reported. The neat acceptors and bulk‐heterojunction blend films with fluorinated donor polymer poly{[4,8‐bis[5‐(2‐ethylhexyl)‐4‐fluoro‐2‐thienyl]benzo[1,2‐b:4,5‐b ′]‐dithiophene‐2,6‐diyl]‐alt‐[2,5‐thiophenediyl[5,7‐bis(2‐ethylhexyl)‐4,8‐dioxo‐4H ,8H‐benzo[1,2‐c :4,5‐c ′]dithiophene‐1,3‐diyl]]} (PBDB‐TF, also known as PM6) are investigated using a battery of techniques, including single crystal X‐ray diffraction, fs transient absorption spectroscopy (fsTA), photovoltaic response, space‐charge‐limited current transport, impedance spectroscopy, grazing incidence wide angle X‐ray scattering, and density functional theory level computation. ITN‐F4 and ITzN‐F4 are found to provide power conversion efficiencies greater and internal reorganization energies less than their non‐π‐extended and nonfluorinated counterparts when paired with PBDB‐TF. Additionally, ITN‐F4 and ITzN‐F4 exhibit favorable bulk‐heterojunction relevant single crystal packing architectures. fsTA reveals that both ITN‐F4 and ITzN‐F4 undergo ultrafast hole transfer (<300 fs) in films with PBDB‐TF, despite excimer state formation in both the neat and blend films. Taken together and in comparison to related structures, these results demonstrate that combined fluorination and π‐extension synergistically promote crystallographic π‐face‐to‐face packing, increase crystallinity, reduce internal reorganization energies, increase interplanar π–π electronic coupling, and increase power conversion efficiency.

In this comprehensive review, the main challenges and the current status of perovskite/silicon, perovskite/CIGS, and perovskite/perovskite tandem technologies are presented. A specific focus is set on advanced characterization methods as well as simulations being utilized for perovskite‐based tandem solar cells to overcome the challenges and gain deeper knowledge to further improve device performance. Finally, the efficiency potentials in different experimental and theoretical limits are compared and pathways toward 35% efficiency are outlined.

Abstract

Tandem solar cells are the next step in the photovoltaic (PV) evolution due to their higher power conversion efficiency (PCE) potential than currently dominating, but inherently limited, single‐junction solar cells. With the emergence of metal halide perovskite absorber materials, the fabrication of highly efficient tandem solar cells, at a reasonable cost, can significantly impact the future PV landscape. The perovskite‐based tandem solar cells have already shown that they can convert light more efficiently than their standalone sub‐cells. However, to reach PCEs over 30%, several challenges have to be overcome and the understanding of this fascinating technology has to be broadened. In this review, the main scientific and engineering challenges in the field are presented, alongside a discussion of the current status of three main perovskite tandem technologies: perovskite/silicon, perovskite/CIGS, and perovskite/perovskite tandem solar cells. A summary of the advanced structural, electrical, optical, radiative, and electronic characterization methods as well as simulations being utilized for perovskite‐based tandem solar cells is presented. The main findings are summarized and the strength of the techniques to overcome the challenges and gain deeper knowledge for further performance improvement is assessed. Finally, the PCE potential in different experimental and theoretical limits is compared with an aim to shed light on the path towards overcoming the 30% efficiency threshold for all of the three herein reviewed tandem technologies.

A comprehensive charge transport characterization of two rigid‐rod conjugated polymers that do not contain single bonds in their backbones is presented. An extended linear backbone structure is visualized by scanning tunneling microscopy. It allows the use of simple solution‐shearing to form uniaxially aligned polymer films with significant mobility anisotropy for current flow parallel and perpendicular to the chain alignment direction.

Abstract

Precise control of the microstructure in organic semiconductors (OSCs) is essential for developing high‐performance organic electronic devices. Here, a comprehensive charge transport characterization of two recently reported rigid‐rod conjugated polymers that do not contain single bonds in the main chain is reported. It is demonstrated that the molecular design of the polymer makes it possible to achieve an extended linear backbone structure, which can be directly visualized by high‐resolution scanning tunneling microscopy (STM). The rigid structure of the polymers allows the formation of thin films with uniaxially aligned polymer chains by using a simple one‐step solution‐shear/bar coating technique. These aligned films show a high optical anisotropy with a dichroic ratio of up to a factor of 6. Transport measurements performed using top‐gate bottom‐contact field‐effect transistors exhibit a high saturation electron mobility of 0.2 cm² V⁻¹ s⁻¹ along the alignment direction, which is more than six times higher than the value reported in the previous work. This work demonstrates that this new class of polymers is able to achieve mobility values comparable to state‐of‐the‐art n‐type polymers and identifies an effective processing strategy for this class of rigid‐rod polymer system to optimize their charge transport properties.

A series of deep‐red/near infrared phosphorescent square‐planar isoquinolinyl pyrazolate Pt(II) complexes modeled by sterically demanding substituents is designed and demonstrates high photoluminescence quantum efficiencies and short excited‐state lifetimes. This allows highly efficient deep‐red/near infrared organic electroluminescence with an external quantum efficiency as high as 30% and peak wavelength of ≈670 nm.

Abstract

The design of square‐planar Pt(II) complexes with highly efficient solid‐state near infrared (NIR) luminescence for electroluminescence is attractive but challenging. This study presents the fine‐turning of excited‐state properties and application of a series of isoquinolinyl pyrazolate Pt(II) complexes that are modulated by steric demanding substituents. It reveals that the bulky substituents do not always disfavor metallophilic Pt···Pt interactions. Instead, π–π stacking among chelates, which are fine‐tuned by the associated substituents, also exerts strong influence to the metal‐metal‐to‐ligand charge transfer (MMLCT) transition character. Theoretical calculations indicate that Pt···Pt contacts become more relevant in the trimers rather than the dimers, especially in their T₁ states, associated with a change from mixed ³LC/³MLCT transition in the monomer/dimer to mixed ³LC/³MMLCT transition character in the trimer. Electroluminescence devices affording intense deep‐red/NIR emission (near 670 nm) with unprecedentedly high external quantum efficiency over 30% are demonstrated. This work provides deep insights into formation MMLCT transition of square‐planar Pt(II) complexes and efficient molecular design for deep‐red/NIR electroluminescence.

An ultrabright solid‐state FR/NIR luminogen with aggregation‐induced emission (AIE) feature is reported. Its resulting AIE dots show good biocompatibility, satisfactory photostability, and a large three‐photon absorption cross section. The AIE dots are reported for visualization of the cerebral thrombosis process of a mouse with intact skull, with high penetration depth and good image contrast.

Abstract

Visualization of the brain in its native environment is important for understanding common brain diseases. Herein, bright luminogens with remarkable aggregation‐induced emission (AIE) characteristics and high quantum yields of up to 42.6% in the solid state are synthesized through facile reaction routes. The synthesized molecule, namely BTF, shows ultrabright far‐red/near‐infrared emission and can be fabricated into AIE dots by a simple nanoprecipitation procedure. Due to their high brightness, large Stokes shift, good biocompatibility, satisfactory photostability, and large three‐photon absorption cross section, the AIE dots can be utilized as efficient fluorescent nanoprobes for in vivo brain vascular imaging through the intact skull by a three‐photon fluorescence microscopy imaging technique. This is the first example of using AIE dots for the visualization of the cerebral stroke process through the intact skull of a mouse with high penetration depth and good image contrast. Such good results are anticipated to open up a new venue in the development of efficient emitters with strong nonlinear optical effects for noninvasive bioimaging of living brain.

Three asymmetric small‐molecule acceptors are developed by changing the fluorine atoms on the terminal group of Y6 to chlorine atoms, namely SY1, SY2, and SY3, with Y6, and Y6‐4Cl are utilized as the reference. Organic solar cells based on the PM6:SY1 blend demonstrate a champion power conversion efficiency of 16.83%. This work can provide a deeper and more comprehensive understanding of applying the asymmetric molecule design method.

Abstract

Small‐molecule acceptors (SMAs)‐based organic solar cells (OSCs) have exhibited great potential for achieving high power conversion efficiencies (PCEs). Meanwhile, developing asymmetric SMAs to improve photovoltaic performance by modulating energy level distribution and morphology has drawn lots of attention. In this work, based on the high‐performance SMA (Y6), three asymmetric SMAs are developed by substituting the fluorine atoms on the terminal group with chlorine atoms, namely SY1 (two F atoms and one Cl atom), SY2 (two F atoms and two Cl atoms), and SY3 (three Cl atoms). Y6 (four F atoms) and Y6‐4Cl (four Cl atoms) are synthesized as control molecules. As a result, SY1 exhibits the shallowest lowest unoccupied molecular orbital energy level and the best molecular packing among these five acceptors. Consequently, OSCs based on PM6:SY1 yield a champion PCE of 16.83% with an open‐circuit voltage (V _OC) of 0.871 V, and a fill factor (FF) of 0.760, which is the best result among the five devices. The highest FF for the PM6:SY1‐based device is mainly ascribed to the most balanced charge transport and optimal morphology. This contribution provides deeper understanding of applying asymmetric molecule design method to further promote PCEs of OSCs.

Ultrasmall highly absorbing NIR‐II polymer dots (Pdots) are reported for the first time for photoacoustic imaging‐guided photothermal therapy. The proposed Pdots possess an ultrasmall particle size (4 nm), excellent photostability, good biocompatibility, bright photoacoustic signals, and high photothermal conversion efficiency (53%) that thus paves a new avenue for the development of organic semiconducting nanoagents for future clinical translation.

Abstract

Phototheranostic agents in the second near‐infrared (NIR‐II) window (1000–1700 nm) are emerging as a promising theranostic platform for precision medicine due to enhanced penetration depth and minimized tissue exposure. The development of metabolizable NIR‐II nanoagents for imaging‐guided therapy are essential for noninvasive disease diagnosis and precise ablation of tumors. Herein, metabolizable highly absorbing NIR‐II conjugated polymer dots (Pdots) are reported for the first time for photoacoustic imaging guided photothermal therapy (PTT). The unique design of low‐bandgap D‐A π‐conjugated polymer (DPP‐BTzTD) together with modified nanoreprecipitation conditions allows to fabricate NIR‐II absorbing Pdots with ultrasmall (4 nm) particle size. Extensive experimental tests demonstrate that the constructed Pdots exhibit good biocompatibility, excellent photostability, bright photoacoustic signals, and high photothermal conversion efficiency (53%). In addition, upon tail‐vein intravenous injection of tumor‐bearing mice, Pdots also show high‐efficient tumor ablation capability with rapid excretion from the body. In particular, both in vitro and in vivo assays indicate that the Pdots possess remarkable PTT performance under irradiation with a 1064 nm laser with 0.5 W cm⁻², which is much lower than its maximum permissible exposure limit of 1 W cm⁻². This pilot study thus paves a novel avenue for the development of organic semiconducting nanoagents for future clinical translation.

In this essay, the construction of high‐performance organic photovoltaics is discussed, with a focus on combining the advantages of new non‐fullerene acceptors and tandem‐junction structure.

Abstract

In consideration of the unique advantages of new non‐fullerene acceptors and the tandem‐junction structure, organic photovoltaics (OPVs) based on them are very promising. Studies related to this emerging area began in 2016 with achieved power conversion efficiencies (PCEs) of 8–10%, which have now been boosted to 17%. In this essay, the construction of high‐performance OPVs is discussed, with a focus on combining the advantages of new non‐fullerene acceptors and the tandem‐junction structure. In order to achieve higher PCEs, methods to enable high short‐circuit current density, open‐circuit voltage, and fill factor are discussed. In addition, the stability and reproducibility of high‐efficiency OPVs are also addressed. Herein, it is forecast that the new non‐fullerene acceptors‐based tandem‐junction OPVs will become the next big wave in the field and achieve high PCEs over 20% in the near future. Some promising research directions on this emerging hot topic are proposed which may further push the field into the 25% high efficiency era and considerably advance the technology beyond laboratory research.

Different concentrations of iridium complexes are introduced into the conjugated backbone of polymer donor PM6 (PM6‐Ir0), this strategy can rationally modify the molecular aggregations, effectively control the blend morphology and physical mechanisms, and finally improve the photovoltaic performance. This work affords an effective approach for further breakthroughs in the reported champion power conversion efficiency of polymer solar cells.

Abstract

The commercially available PM6 as donor materials are used widely in highly efficient nonfullerene polymer solar cells (PSCs). In this work, different concentrations of iridium (Ir) complexes (0, 0.5, 1, 2.5, and 5 mol%) are incorporated carefully into the polymer conjugated backbone of PM6 (PM6‐Ir0), and a set of π‐conjugated polymer donors (named PM6‐Ir0.5, PM6‐Ir1, PM6‐Ir2.5, and PM6‐Ir5) are synthesized and characterized. It is demonstrated that the approach can rationally modify the molecular aggregations of polymer donors, effectively controlling the corresponding blend morphology and physical mechanisms, and finally improve the photovoltaic performance of the PM6‐Irx‐based PSCs. Among them, the best device based on PM6‐Ir1:Y6 (1:1.2, w/w) exhibits outstanding power conversion efficiencies (PCEs) of 17.24% tested at Wuhan University and 17.32% tested at Institute of Chemistry, Chinese Academy of Sciences as well as a certified PCE of 16.70%, which are much higher than that of the control device based on the PM6‐Ir0:Y6 blend (15.39%). This work affords an effective approach for further break through the reported champion PCE of the binary PSCs.

The active layer morphology of all‐small‐molecule organic solar cells (SM‐OSCs) is tuned by side chain engineering of the donor molecules and thermal annealing (TA) of the devices. An SM‐OSC based on A–D–A‐structured SM1‐F with fluorine and alkyl substituents as the donor and Y6 as the acceptor, and with TA, demonstrates a high power conversion efficiency of 14.07%.

Abstract

It is very important to fine‐tune the nanoscale morphology of donor:acceptor blend active layers for improving the photovoltaic performance of all‐small‐molecule organic solar cells (SM‐OSCs). In this work, two new small molecule donor materials are synthesized with different substituents on their thiophene conjugated side chains, including SM1‐S with alkylthio and SM1‐F with fluorine and alkyl substituents, and the previously reported donor molecule SM1 with an alkyl substituent, for investigating the effect of different conjugated side chains on the molecular aggregation and the photophysical, and photovoltaic properties of the donor molecules. As a result, an SM1‐F‐based SM‐OSC with Y6 as the acceptor, and with thermal annealing (TA) at 120 °C for 10 min, demonstrates the highest power conversion efficiency value of 14.07%, which is one of the best values for SM‐OSCs reported so far. Besides, these results also reveal that different side chains of the small molecules can distinctly influence the crystallinity characteristics and aggregation features, and TA treatment can effectively fine‐tune the phase separation to form suitable donor–acceptor interpenetrating networks, which is beneficial for exciton dissociation and charge transportation, leading to highly efficient photovoltaic performance.

End‐group π−π stacking is proved to be able to effectively reduce the singlet−triplet energy difference in narrow‐bandgap A−D−A acceptors, which is beneficial in simultaneously decreasing the voltage loss in exciton dissociation and suppressing triplet recombination. Furthermore, the absorption spectra can be broadened or redshifted, thus improving the light‐harvesting efficiencies. These results pave the way toward high‐efficiency organic photovoltaics.

Abstract

To improve the power conversion efficiencies for organic solar cells, it is necessary to enhance light absorption and reduce energy loss simultaneously. Both the lowest singlet (S1) and triplet (T1) excited states need to energertically approach the charge‐transfer state to reduce the energy loss in exciton dissociation and by triplet recombination. Meanwhile, the S1 energy needs to be decreased to broaden light absorption. Therefore, it is imperative to reduce the singlet−triplet energy gap (ΔE _ST), particularly for the narrow‐bandgap materials that determine the device T1 energy. Although maximizing intramolecular push−pull effect can drastically decrease ΔE _ST, it inevitably results in weak oscillator strength and light absorption. Herein, large oscillator strength (≈3) and a moderate ΔE _ST (0.4−0.5 eV) are found for state‐of‐the‐art A−D−A small‐molecule acceptors (ITIC, IT‐4F, and Y6) owing to modest push−pull effect. Importantly, end‐group π−π stacking commonly in the films can substantially decrease the S1 energy by nearly 0.1 eV, but the T1 energy is hardly changed. The obtained reduction of ΔE _ST is crucial to effectively suppress triplet recombination and acquire small exciton dissociation driving force. Thus, end‐group π−π stacking is an effective way to achieve both small energy loss and efficient light absorption for high‐efficiency organic photovoltaics.

Nature Communications, Published online: 21 April 2020; doi:10.1038/s41467-020-15681-3

Symmetric multibranched donor-acceptor molecules are promising photoactive materials for diverse applications. Here the authors show that, in octupolar and quadrupolar dyes, excited-state symmetry breaking occurs efficiently in polar solvents only and results in a concentration of the excitation that may trigger fast photochemical reactions.

Nature Communications, Published online: 23 April 2020; doi:10.1038/s41467-020-15826-4

There lacks a comprehensive analysis on the large-scale deployment of solar photovoltaic projects and its impact on poverty alleviation. Here the authors show that solar photovoltaic poverty alleviation pilot policy increases per-capita disposable income in a county by approximately 7%-8%.

A fused‐ring electron acceptor, FINIC, with fluorination of both end groups and side chains is designed and synthesized, and compared with its nonfluorinated analogue, INIC. FINIC exhibits 3D molecular stacking, exciton transport and charge transport. FINIC‐based organic solar cells yield an efficiency of 14.0%, far exceeding that of the INIC‐based devices (5.1%).

Abstract

A new fluorinated electron acceptor (FINIC) based on 6,6,12,12‐tetrakis(3‐fluoro‐4‐hexylphenyl)‐indacenobis(dithieno[3,2‐b ;2′ ,3′ ‐d ]thiophene) as the electron‐donating central core and 5,6‐difluoro‐3‐(1,1‐dicyanomethylene)‐1‐indanone as the electron‐deficient end groups is rationally designed and synthesized. FINIC shows similar absorption profile in dilute solution to the nonfluorinated analogue INIC. However, compared with INIC, FINIC film shows red‐shifted absorption, down‐shifted frontier molecular orbital energy levels, enhanced crystallinity, and more ordered molecular packing. Single‐crystal structure data show that FINIC molecules pack into closer 3D “network” motif through H‐bonding and π–π interaction, while INIC molecules pack into incompact “honeycomb” motif through only π–π stacking. Theoretical calculations reveal that FINIC has stronger electronic coupling and more molecular interactions than INIC. FINIC has higher electron mobilities in both horizontal and vertical directions than INIC. Moreover, FINIC and INIC support efficient 3D exciton transport. PBD‐SF/FINIC blend has a larger driving force for exciton splitting, more efficient charge transfer and photoinduced charge generation. Finally, the organic solar cells based on PBD‐SF/FINIC blend yield power conversion efficiency of 14.0%, far exceeding that of the PBD‐SF/INIC‐based devices (5.1%).