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Showing papers on "Organic semiconductor published in 2022"


Journal ArticleDOI
TL;DR: In this article , the conjugated polymer PM6 was matched with Y6 or PCBM electron acceptors and achieved external quantum efficiencies of 1.7% to 2.6% at 400 to 700 nm, respectively.
Abstract: Organic semiconductor photocatalysts for the production of solar fuels are attractive as they can be synthetically tuned to absorb visible light while simultaneously retaining suitable energy levels to drive a range of processes. However, a greater understanding of the photophysics that determines the function of organic semiconductor heterojunction nanoparticles is needed to optimize performance. Here, we show that such materials can intrinsically generate remarkably long-lived reactive charges, enabling them to efficiently drive sacrificial hydrogen evolution. Our optimized hetereojunction photocatalysts comprise the conjugated polymer PM6 matched with Y6 or PCBM electron acceptors, and achieve external quantum efficiencies of 1.0% to 5.0% at 400 to 900 nm and 8.7% to 2.6% at 400 to 700 nm, respectively. Employing transient and operando spectroscopies, we find that the heterojunction structure in these nanoparticles greatly enhances the generation of long-lived charges (millisecond to second timescale) even in the absence of electron/hole scavengers or Pt. Such long-lived reactive charges open potential applications in water-splitting Z-schemes and in driving kinetically slow and technologically desirable oxidations. Organic semiconductor heterojunction photocatalysts are promising for synthesis of solar fuels yet a deeper understanding of their underlying photophysics is needed to improve performance. Here, the authors show that such materials can intrinsically generate remarkably long-lived reactive charges, enabling them to efficiently drive hydrogen evolution.

97 citations


Journal ArticleDOI
TL;DR: In this article , the development of NIR-absorbing materials for OPVs is reviewed, and the structure-property relationship between various kinds of donor (D, A units and absorption window are constructed to satisfy requirements for different applications.
Abstract: Near-infrared (NIR)-absorbing organic semiconductors have opened up many exciting opportunities for organic photovoltaic (OPV) research. For example, new chemistries and synthetical methodologies have been developed; especially, the breakthrough Y-series acceptors, originally invented by our group, specifically Y1, Y3, and Y6, have contributed immensely to boosting single-junction solar cell efficiency to around 19%; novel device architectures such as tandem and transparent organic photovoltaics have been realized. The concept of NIR donors/acceptors thus becomes a turning point in the OPV field. Here, the development of NIR-absorbing materials for OPVs is reviewed. According to the low-energy absorption window, here, NIR photovoltaic materials (p-type (polymers) and n-type (fullerene and nonfullerene)) are classified into four categories: 700-800 nm, 800-900 nm, 900-1000 nm, and greater than 1000 nm. Each subsection covers the design, synthesis, and utilization of various types of donor (D) and acceptor (A) units. The structure-property relationship between various kinds of D, A units and absorption window are constructed to satisfy requirements for different applications. Subsequently, a variety of applications realized by NIR materials, including transparent OPVs, tandem OPVs, photodetectors, are presented. Finally, challenges and future development of novel NIR materials for the next-generation organic photovoltaics and beyond are discussed.

67 citations


Journal ArticleDOI
TL;DR: In this paper , the authors present a review of recent approaches to confer stretchability to polymer semiconductors while maintaining high charge carrier mobilities, with emphasis on the control of both polymer-chain dynamics and thin-film morphology.
Abstract: Stretchable polymer semiconductors have advanced rapidly in the past decade as materials required to realize conformable and soft skin-like electronics become available. Through rational molecular-level design, stretchable polymer semiconductor films are now able to retain their electrical functionalities even when subjected to repeated mechanical deformations. Furthermore, their charge-carrier mobilities are on par with the best flexible polymer semiconductors, with some even exceeding that of amorphous silicon. The key advancements are molecular-design concepts that allow multiple strain energy-dissipation mechanisms, while maintaining efficient charge-transport pathways over multiple length scales. In this perspective article, we review recent approaches to confer stretchability to polymer semiconductors while maintaining high charge carrier mobilities, with emphasis on the control of both polymer-chain dynamics and thin-film morphology. Additionally, we present molecular design considerations toward intrinsically elastic semiconductors that are needed for reliable device operation under reversible and repeated deformation. A general approach involving inducing polymer semiconductor nanoconfinement allows for incorporation of several other desired functionalities, such as biodegradability, self-healing, and photopatternability, while enhancing the charge transport. Lastly, we point out future directions, including advancing the fundamental understanding of morphology evolution and its correlation with the change of charge transport under strain, and needs for strain-resilient polymer semiconductors with high mobility retention.

66 citations


Journal ArticleDOI
TL;DR: In this paper , the energy levels of 33 organic semiconductors via cyclic voltammetry (CV), density functional theory, ultraviolet photoelectron spectroscopy, and low-energy inverse photovoltaic spectrograph (PES) were determined.
Abstract: The frontier molecular energy levels of organic semiconductors are decisive for their fundamental function and efficiency in optoelectronics. However, the precise determination of these energy levels and their variation when using different techniques makes it hard to compare and establish design rules. In this work, the energy levels of 33 organic semiconductors via cyclic voltammetry (CV), density functional theory, ultraviolet photoelectron spectroscopy, and low‐energy inverse photoelectron spectroscopy are determined. Solar cells are fabricated to obtain key device parameters and relate them to the significant differences in the energy levels and offsets obtained from different methods. In contrast to CV, the photovoltaic gap measured using photoelectron spectroscopy (PES) correlates well with the experimental device VOC. It is demonstrated that high‐performing systems such as PM6:Y6 and WF3F:Y6, which are previously reported to have negligible ionization energy (IE) offsets (ΔIE), possess sizable ΔIE of ≈0.5 eV, determined by PES. Using various D–A blends, it is demonstrated that ΔIE plays a key role in charge generation. In contrast to earlier reports, it is shown that a vanishing ΔIE is detrimental to device performance. Overall, these findings establish a solid base for reliably evaluating material energetics and interpreting property–performance relationships in organic solar cells.

40 citations


Journal ArticleDOI
TL;DR: In this paper , the authors showed that 60-90% of excitons form free charges at AM 1.5 light intensity in single-component Y6 photovoltaics.
Abstract: Organic photovoltaics (OPVs) promise cheap and flexible solar energy. Whereas light generates free charges in silicon photovoltaics, excitons are normally formed in organic semiconductors due to their low dielectric constants, and require molecular heterojunctions to split into charges. Recent record efficiency OPVs utilise the small molecule, Y6, and its analogues, which - unlike previous organic semiconductors - have low band-gaps and high dielectric constants. We show that, in Y6 films, these factors lead to intrinsic free charge generation without a heterojunction. Intensity-dependent spectroscopy reveals that 60-90% of excitons form free charges at AM1.5 light intensity. Bimolecular recombination, and hole traps constrain single component Y6 photovoltaics to low efficiencies, but recombination is reduced by small quantities of donor. Quantum-chemical calculations reveal strong coupling between exciton and CT states, and an intermolecular polarisation pattern that drives exciton dissociation. Our results challenge how current OPVs operate, and renew the possibility of efficient single-component OPVs.

32 citations


Journal ArticleDOI
TL;DR: In this article , the effect of load pressure, sliding speed, and device size on the performance of PEDOT: PSS/Al alloy DC TENGs was investigated.

25 citations


Journal ArticleDOI
TL;DR: In this paper , a stretchable semiconductor for organic electrochemical transistors (OECTs) is reported, which gives exceptional stretchability over 200% strain and 5000 repeated stretching cycles, together with OECT performance on par with the state of the art.
Abstract: Organic electrochemical transistors (OECTs) represent an emerging device platform for next‐generation bioelectronics owing to the uniquely high amplification and sensitivity to biological signals. For achieving seamless tissue–electronics interfaces for accurate signal acquisition, skin‐like softness and stretchability are essential requirements, but they have not yet been imparted onto high‐performance OECTs, largely due to the lack of stretchable redox‐active semiconducting polymers. Here, a stretchable semiconductor is reported for OECT devices, namely poly(2‐(3,3′‐bis(2‐(2‐(2‐methoxyethoxy)ethoxy)ethoxy)‐[2,2′‐bithiophen]‐5)yl thiophene) (p(g2T‐T)), which gives exceptional stretchability over 200% strain and 5000 repeated stretching cycles, together with OECT performance on par with the state‐of‐the‐art. Validated by systematic characterizations and comparisons of different polymers, the key design features of this polymer that enable the combination of high stretchability and high OECT performance are a nonlinear backbone architecture, a moderate side‐chain density, and a sufficiently high molecular weight. Using this highly stretchable polymer semiconductor, an intrinsically stretchable OECT is fabricated with high normalized transconductance (≈223 S cm−1) and biaxial stretchability up to 100% strain. Furthermore, on‐skin electrocardiogram (ECG) recording is demonstrated, which combines built‐in amplification and unprecedented skin conformability.

25 citations


Journal ArticleDOI
TL;DR: In this paper, an organic semiconductor poly(3,4-ethylene dioxythiophene): poly(styrene sulfonate) (PEDOT: PSS) was used as a friction layer to make a direct current (DC) power source generated through triboelectric effect.

25 citations


Journal ArticleDOI
TL;DR: In this paper , the authors show the recent progress in the development of n-type OSCs with the key π-electron core (π-core) of benzo[de]isoquinolino[1,8-gh]quinolinetetetracarboxylic diimide (BQQDI) on the basis of single-crystal OTFT technologies and the band-transport model enabled by two-dimensional molecular packing arrangements.
Abstract: ConspectusOrganic semiconductors (OSCs) have attracted much attention because of their potential applications for flexible and printed electronic devices and thus have been extensively investigated in a variety of research fields, such as organic chemistry, solid-state physics, and device physics and engineering. Organic thin-film transistors (OTFTs), a class of OSC-based devices, have been expected to be an alternative of silicon-based metal oxide semiconductor field-effect transistors (MOSFETs), which is the indispensable element for most of the current electronic devices. However, the noncovalently aggregated, van der Waals solid nature of the OSCs, by contrast to covalently bound silicon, conventionally exhibits lower carrier mobilities, limiting the practical applications of OTFTs. In particular, electron-transporting (i.e., n-type) OSCs lag behind their hole-transporting (p-type) counterparts in carrier mobility and ambient stability as OTFTs. This is primarily because of the difficulty in achieving compatibility between the aggregated structure exhibiting excellent carrier mobility and that with enough electron affinity. Recent understandings of carrier transport in OSCs explain that large and two-dimensionally isotropic transfer integrals coupled with small fluctuations are crucial for high carrier mobilities. In addition, from a practical point of view, the compatibility with practical device processes is highly required. Rational molecular design principles, therefore, are still demanded for developing OSCs and OTFTs toward high-end device applications.Herein, we will show our recent progress in the development of n-type OSCs with the key π-electron core (π-core) of benzo[de]isoquinolino[1,8-gh]quinolinetetracarboxylic diimide (BQQDI) on the basis of single-crystal OTFT technologies and the band-transport model enabled by two-dimensional molecular packing arrangements. The critical point is the introduction of electronegative nitrogen atoms into the π-core: the nitrogen atoms in BQQDI not only deepen the molecular orbital energies but also allow hydrogen-bonding-like attractive intermolecular interactions to control the aggregated structures, unlike the conventional role of the nitrogen introduced into OSCs only for the former role. Hence, the BQQDI analogues exhibit air-stable OTFT behavior and two-dimensional brickwork packing structures. Specifically, phenethyl-substituted analogue (PhC2-BQQDI) has been shown as the first principal BQQDI-based material, demonstrating solution-processable thin-film single crystals, fewer anisotropic transfer integrals, and an effective suppression of molecular motions, leading to band-like electron-transport properties and stress-durable n-channel OTFT performances, in conjunction with the support of computational calculations. Insights into more fundamental points of view have been found by side-chain derivatization and OTFT studies on polycrystalline and single-crystal films. We hope that this Account provides readers with new strategies for designing high-performance OSCs by two-dimensional control of the aggregated structures.

25 citations


Journal ArticleDOI
TL;DR: In this paper , a series of all-organic dielectric polymer composites have been fabricated by blending the n-type molecular semiconductor 1,4,5,8−naphthalenetetracarboxylic dianhydride (NTCDA) with polyetherimide (PEI).
Abstract: High‐temperature dielectric polymers are in constant demand for the multitude of high‐power electronic devices employed in hybrid vehicles, grid‐connected photovoltaic and wind power generation, to name a few. There is still a lack, however, of dielectric polymers that can work at high temperature (> 150 °C). Herein, a series of all‐organic dielectric polymer composites have been fabricated by blending the n‐type molecular semiconductor 1,4,5,8‐naphthalenetetracarboxylic dianhydride (NTCDA) with polyetherimide (PEI). Electron traps are created by the introduction of trace amounts of n‐type small molecule semiconductor NTCDA into PEI, which effectively reduces the leakage current and improves the breakdown strength and energy storage properties of the composite at high temperature. Especially, excellent energy storage performance is achieved in 0.5 vol.% NTCDA/PEI at the high temperatures of 150 and 200 °C, e.g., ultrahigh discharge energy density of 5.1 J cm−3 at 150 °C and 3.2 J cm−3 at 200 °C with high discharge efficiency of 85–90%, which is superior to its state‐of‐the‐art counterparts. This study provides a facile and effective strategy for the design of high‐temperature dielectric polymers for advanced electronic and electrical systems.

24 citations


Journal ArticleDOI
TL;DR: In this paper , a review of the five-ring-fused organic prototype molecules and their derivatives are summarized to provide a general understanding of this catalogue material for application in organic field-effect transistors.
Abstract: Organic molecular semiconductors have been paid great attention due to their advantages of low-temperature processability, low fabrication cost, good flexibility, and excellent electronic properties. As a typical example of five-ring-fused organic semiconductors, a single crystal of pentacene shows a high mobility of up to 40 cm2 V-1 s-1, indicating its potential application in organic electronics. However, the photo- and optical instabilities of pentacene make it unsuitable for commercial applications. But, molecular engineering, for both the five-ring-fused building block and side chains, has been performed to improve the stability of materials as well as maintain high mobility. Here, several groups (thiophenes, pyrroles, furans, etc.) are introduced to design and replace one or more benzene rings of pentacene and construct novel five-ring-fused organic semiconductors. In this review article, ∼500 five-ring-fused organic prototype molecules and their derivatives are summarized to provide a general understanding of this catalogue material for application in organic field-effect transistors. The results indicate that many five-ring-fused organic semiconductors can achieve high mobilities of more than 1 cm2 V-1 s-1, and a hole mobility of up to 18.9 cm2 V-1 s-1 can be obtained, while an electron mobility of 27.8 cm2 V-1 s-1 can be achieved in five-ring-fused organic semiconductors. The HOMO-LUMO levels, the synthesis process, the molecular packing, and the side-chain engineering of five-ring-fused organic semiconductors are analyzed. The current problems, conclusions, and perspectives are also provided.

Journal ArticleDOI
TL;DR: In this paper , the authors report the achievement of high-mobility organic semiconductors based on existing polycyclic aromatic hydrocarbons with B-N bonds through a "periphery engineering" strategy.
Abstract: Despite the remarkable synthetic accomplishments in creating diverse polycyclic aromatic hydrocarbons with B-N bonds (BN-PAHs), their optoelectronic applications have been less exploited. Herein, we report the achievement of high-mobility organic semiconductors based on existing BN-PAHs through a "periphery engineering" strategy. Tetraphenyl- and diphenyl-substituted BN-anthracenes (TPBNA and DPBNA, respectively) are designed and synthesized. DPBNA exhibits the highest hole mobility of 1.3 cm 2 V -1 s -1 in organic field-effect transistors, significantly outperforming TPBNA and all the reported BN-PAHs. Remarkably, this is the first BN-PAH with mobility over 1 cm 2 V -1 s -1 , which is a benchmark value for practical applications as compared with amorphous silicon. Furthermore, high-performance phototransistors based on DPBNA are also demonstrated, implying the high potential of BN-PAHs for optoelectronic applications when the "periphery engineering" strategy is implemented.



Journal ArticleDOI
TL;DR: In this article , a planar-conjugated covalent organic framework (COF) was developed using planar building blocks, and a wafer-scale self-supporting thin COF was grown, which could be transferred onto any of the desired substrates.
Abstract: : A tunable topology and a porous network make π conjugated covalent organic frameworks (COFs) a new class of organic semiconductors for optoelectronic, smart sensing, and catalytic applications. Although some of the COFs exhibit enhanced electric conductivity with a high charge carrier mobility, the nature and pathways of charge transport still remain elusive. In order to unveil the transport mechanism, herein, we have developed crystalline π -conjugated COFs using planar building blocks, and a wafer-scale self-supporting thin fi lm was grown, which could be transferred onto any of the desired substrates. The COF fi lm was found to be highly oriented and exhibited a high in-plane electronic conductivity. The conductivity was almost independent of temperature with an ultra-low activation energy of 14.3 meV, approaching a band-like transport of charge carriers within the crystalline domains. The COF fi lms also showed a high photoresponsivity in electronic conduction against a complete visible range, demonstrated as a fl exible photodetector device. This work represents a thorough investigation of the mechanism and direction of charge transport in crystalline π -conjugated COF semiconductors, which suggests their feasibility as key active materials in multi-functional organic electronics. of di ff erent wavelengths, and the photocurrent was measured in a cryostat (Montana, Cryostation) under temper- ature control. The illuminating light power was measured using an optical power meter (S130VC Photodiode Power Sensor, Thorlabs). Other details of the photoconductivity measurements are described in the Supporting Information..

Journal ArticleDOI
TL;DR: In this paper , a typical class of organic semiconductors demonstrate unique optical, electrical, magnetic and other interesting properties due to their extended conjugation and diverse structures, such as polycyclic aromatic hydrocarbons (PAHs).
Abstract: Polycyclic aromatic hydrocarbons (PAHs) as a typical class of organic semiconductors demonstrate unique optical, electrical, magnetic and other interesting properties due to their extended conjugation and diverse structures.

Journal ArticleDOI
TL;DR: This study uses a solvothermal approach with excess hydrazine hydrate to concurrently reduce and dissolve rigid-backbone perylene diimide (PDI) crystallites into the soluble dianion species with a remarkably high reduction potential, suggesting that the long-range ferromagnetic ordering can survive at room-temperature in organic semiconductors.
Abstract: The development of pure organic magnets with high Curie temperatures remains a challenging task in material science. Introducing high‐density free radicals to strongly interacting organic molecules may be an effective method to this end. In this study, a solvothermal approach with excess hydrazine hydrate is used to concurrently reduce and dissolve rigid‐backbone perylene diimide (PDI) crystallites into the soluble dianion species with a remarkably high reduction potential. The as‐prepared PDI powders comprising radical anion aggregates are fabricated by a subsequent self‐assembly and spontaneous oxidation process. The results of magnetic measurements show that the PDI powders exhibit room‐temperature ferromagnetism and a Curie temperature higher than 400 K, with a vast saturation magnetization that reaches ≈1.2 emu g−1. Elemental analysis along with the diamagnetic signal of the ablated residue are used to rule out the possibility that the magnetism is due to metal contamination. The findings suggest that the long‐range ferromagnetic ordering can survive at room‐temperature in organic semiconductors, and offers a new optional way to create room‐temperature magnetic semiconductors.

Journal ArticleDOI
TL;DR: In this paper , an organic solar cell was constructed by doping n-type DMBI-BDZC into one host binary bulk heterojunction (BHJ) photoactive layer comprised of a polymer donor PM6 and a nonfullerene acceptor Y6.

Journal ArticleDOI
TL;DR: In this article , the authors presented organic bipolar transistors with outstanding device performance: a previously undescribed vertical architecture and highly crystalline organic rubrene thin films yield devices with high differential amplification (more than 100) and superior highfrequency performance over conventional devices.
Abstract: Abstract Devices made using thin-film semiconductors have attracted much interest recently owing to new application possibilities. Among materials systems suitable for thin-film electronics, organic semiconductors are of particular interest; their low cost, biocompatible carbon-based materials and deposition by simple techniques such as evaporation or printing enable organic semiconductor devices to be used for ubiquitous electronics, such as those used on or in the human body or on clothing and packages 1–3 . The potential of organic electronics can be leveraged only if the performance of organic transistors is improved markedly. Here we present organic bipolar transistors with outstanding device performance: a previously undescribed vertical architecture and highly crystalline organic rubrene thin films yield devices with high differential amplification (more than 100) and superior high-frequency performance over conventional devices. These bipolar transistors also give insight into the minority carrier diffusion length—a key parameter in organic semiconductors. Our results open the door to new device concepts of high-performance organic electronics with ever faster switching speeds.

Journal ArticleDOI
TL;DR: In this paper , a lattice mismatch-free concept is defined for hierarchical self-assembly of organic semiconductor molecules, allowing for the large-scale synthesis of organic heterostructure nanowires composed of the organic alloys and cocrystals.
Abstract: Organic heterostructure nanowires, such as multiblock, core/shell, branch-like and related compounds, have attracted chemists' extensive attention because of their novel physicochemical properties. However, owing to the difficulty in solving the lattice mismatch of distinct molecules, the construction of organic heterostructures at large scale remains challenging, which restricts its wide use in future applications. In this work, we define a concept of lattice-mismatch-free for hierarchical self-assembly of organic semiconductor molecules, allowing for the large-scale synthesis of organic heterostructure nanowires composed of the organic alloys and cocrystals. Thus, various types of organic triblock nanowires are prepared in large scale, and the length ratio of different segments of the triblock nanowires can be precisely regulated by changing the stoichiometric ratio of different components. These results pave the way towards fine synthesis of heterostructures in a large scale and facilitate their applications in organic optoelectronics at micro/nanoscale.

Journal ArticleDOI
TL;DR: In this paper , the authors conduct an in-depth review of external force-based, additive-based and binary solvent-based techniques to effectively control the organic semiconductor crystallization, thin-film morphology, and crystal orientations.

Journal ArticleDOI
TL;DR: In this paper , a series of color-tunable, highmobility, emissive, organic semiconductors via molecular doping with a high-mobility organic semiconductor, 2,6-diphenylanthracene, as the host.
Abstract: Developing high-mobility emissive organic semiconductors with tunable colors is crucial for organic light-emitting transistors (OLETs), a pivotal component of integrated optoelectronic devices, but remains a great challenge. Here, we demonstrate a series of color-tunable, high-mobility, emissive, organic semiconductors via molecular doping with a high-mobility organic semiconductor, 2,6-diphenylanthracene, as the host. The well-matched molecular structures and sizes with efficient energy transfer between the host and guest enable the intrinsically high charge transport with tunable colors. High mobility with the highest value >2 cm2 V−1 s−1 and strong emission with photoluminescence quantum yield >15.8% are obtained for these molecular-doped organic semiconductors. Last, a large color gamut for constructed OLETs is up to 59% National Television System Committee standard, meanwhile with an extremely high current density approaching 326.4 kA cm−2, showing great potential for full-color smart display, organic electrically pumped lasers and other related logic circuitries.

Journal ArticleDOI
TL;DR: In this article , the donor core of non-fullerene acceptors (NFAs) is extended from a heptacyclic unit to a nonacyclics unit to suppress trap states in OSCs.
Abstract: The high trap density (generally 1016 to 1018 cm−3) in thin films of organic semiconductors is the primary reason for the inferior charge‐carrier mobility and large nonradiative recombination energy loss (ΔEnr) in organic solar cells (OSCs), limiting improvement in power conversion efficiencies (PCEs). In this study, the trap density in OSCs is efficiently reduced via extending the donor core of nonfullerene acceptors (NFAs) from a heptacyclic unit to a nonacyclic unit. TTPIC‐4F with a nonacyclic unit has stronger intramolecular and intermolecular interactions, affording higher crystallinity in thin films relative to its counterpart BTPIC‐4F. Thus, the D18:TTPIC‐4F‐based device achieves a lower trap density of 4.02 × 1015 cm−3, comparable to some typical high‐performance inorganic/hybrid semiconductors, with higher mobility and inhibited charge‐carrier recombination in devices. Therefore, the D18:TTPIC‐4F‐based OSC exhibits an impressive PCE of 17.1% with a low ΔEnr of 0.208 eV, which is the best known value for A–D–A‐type NFAs. Therefore, extending the donor core of NFAs is an efficient method for suppressing trap states in OSCs for high PCEs.

Journal ArticleDOI
TL;DR: In this paper , two medium bandgap (MBG) electron acceptors, TPT4F and TPT 4Cl, are developed via the new design of multi-noncovalent interaction assisted unfused core, flanked with two electron withdrawing end groups.

Journal ArticleDOI
24 Jan 2022-Crystals
TL;DR: In this paper , the authors summarized the properties of Y6 materials and the seven critical methods modifying the Y6 structure to improve the power-conversion efficiency (PCE) developed in the latest three years as well as the basic principles and parameters of OSCs.
Abstract: Non-fullerene acceptors are promising to achieve high efficiency in organic solar cells (OSCs). Y6-based acceptors, one group of new n-type semiconductors, have triggered tremendous attention when they reported a power-conversion efficiency (PCE) of 15.7% in 2019. After that, scientists are trying to improve the efficiency in different aspects including choosing new donors, tuning Y6 structures, and device engineering. In this review, we first summarize the properties of Y6 materials and the seven critical methods modifying the Y6 structure to improve the PCEs developed in the latest three years as well as the basic principles and parameters of OSCs. Finally, the authors would share perspectives on possibilities, necessities, challenges, and potential applications for designing multifunctional organic device with desired performances via machine learning.

Journal ArticleDOI
TL;DR: It is demonstrated that the injection-dependent emission line-shape in organic semiconductors is primarily associated with a state-filling effect, where the extent of spectral blue-shift can be a strong indicator for energetic disorder.
Abstract: The power conversion efficiency of organic photovoltaics is strongly limited by relatively large energy loss, which is partially due to the disordered nature of organic semiconductors. This disordered nature not only hinders the rational design of molecules with excellent photophysical properties but also prevents a more thorough understanding of the inherent link between microscopic parameters and physical phenomena. In this Perspective, we demonstrate that the injection-dependent emission line-shape in organic semiconductors is primarily associated with a state-filling effect, where the extent of spectral blue-shift can be a strong indicator for energetic disorder. Molecular geometry with rigidity and coplanarity not only promotes preferential face-on stacking that narrows the energetic distribution of subgap states but also impedes torsional deformations of the conjugated backbone away from planarity, thereby facilitating larger π-electron delocalization. These structural characteristics explain the seemingly contradictory high radiative efficiency of low-bandgap nonfullerene molecules, providing promising molecular design strategies to realize high-efficiency organic photovoltaics.

Journal ArticleDOI
TL;DR: In this paper , a strain balance strategy was proposed to stabilize the aggregate state by regulating film thickness, which is based on the unique transition from tensile strain to compressive strain with increasing film thickness.
Abstract: The instability of organic field-effect transistors (OFETs) is one key obstacle to practical application and is closely related to the unstable aggregate state of organic semiconductors (OSCs). However, the underlying reason for this instability remains unclear, and no effective solution has been developed. Herein, we find that the intrinsic tensile and compressive strains that exist in OSC films are the key origins for aggregate state instability and device degradation. We further report a strain balance strategy to stabilize the aggregate state by regulating film thickness, which is based on the unique transition from tensile strain to compressive strain with increasing film thickness. Consequently, a strain-free and ultrastable OSC film is obtained by regulating the film thickness, with which an ultrastable OFET with a five-year lifetime is realized. This work provides a deeper understanding of and a solution to the instability of OFETs and sheds light on their industrialization.

Journal ArticleDOI
TL;DR: A correct determination of the ionization potential and electron affinity (EA) as well as the energy gap is essential to properly characterize a series of key phenomena related to the electron affinity as discussed by the authors .
Abstract: A correct determination of the ionization potential (IP) and electron affinity (EA) as wells as the energy gap is essential to properly characterize a series of key phenomena related to...

Journal ArticleDOI
TL;DR: In this paper , the authors reported three high-mobility semiconducting polymers with different spin ground states and showed that the electronic structure, spin density, and solid-state interchain interactions in the high-spin polymers are crucial for their ground states.
Abstract: Organic semiconductors with high-spin ground states are fascinating because they could enable fundamental understanding on the spin-related phenomenon in light element and provide opportunities for organic magnetic and quantum materials. Although high-spin ground states have been observed in some quinoidal type small molecules or doped organic semiconductors, semiconducting polymers with high-spin at their neutral ground state are rarely reported. Here we report three high-mobility semiconducting polymers with different spin ground states. We show that polymer building blocks with small singlet-triplet energy gap (ΔES-T) could enable small ΔES-T gap and increase the diradical character in copolymers. We demonstrate that the electronic structure, spin density, and solid-state interchain interactions in the high-spin polymers are crucial for their ground states. Polymers with a triplet ground state (S = 1) could exhibit doublet (S = 1/2) behavior due to different spin distributions and solid-state interchain spin-spin interactions. Besides, these polymers showed outstanding charge transport properties with high hole/electron mobilities and can be both n- and p-doped with superior conductivities. Our results demonstrate a rational approach to obtain high-mobility semiconducting polymers with different spin ground states.

Journal ArticleDOI
TL;DR: In this article , a solution-processed PQD/OSC PHJ was used to construct photodiodes working in self-powered mode, with a broad range photoresponse from ultraviolet to near-infrared, with responsivity approaching 10−1 A W−1 and detectivity over 106 Jones.
Abstract: Planar heterojunctions (PHJs) are fundamental building blocks for construction of semiconductor devices. However, fabricating PHJs with solution‐processable semiconductors such as organic semiconductors (OSCs) is a challenge. Herein, utilizing the orthogonal solubility and good wettability between CsPbBr3 perovskite quantum dots (PQDs) and OSCs, fabrication of solution‐processed PQD/OSC PHJs are reported. The phototransistors based on bilayer PQD/PDVT‐10 PHJs show responsivity up to 1.64 × 104 A W−1, specific detectivity of 3.17 × 1012 Jones, and photosensitivity of 5.33 × 106 when illuminated by 450 nm light. Such high photodetection performance is attributed to efficient charge dissociation and transport, as well as the photogating effect in the PHJs. Furthermore, the tri‐layer PDVT‐10/PQD/Y6 PHJs are used to construct photodiodes working in self‐powered mode, which exhibit broad range photoresponse from ultraviolet to near‐infrared, with responsivity approaching 10−1 A W−1 and detectivity over 106 Jones. These results present a convenient and scalable production processes for solution‐processed PHJs and show their great potential for optoelectronic applications.