Shirakawa, MacDiarmid and Heeger received the 2000 Nobel Prize in Chemistry for the discovery of conducting polymers. Here we summarize the impact of (semi)conducting polymers on fundamental ...research, synthetic accessibility at scale, industrial applicability and the future.
Conspectus In the last three decades, p-type (hole-transporting) organic and polymeric semiconductors have achieved great success in terms of materials diversity and device performance, while the ...development of n-type (electron-transporting) analogues greatly lags behind, which is limited by the scarcity of highly electron-deficient building blocks with compact geometry and good solubility. However, such n-type semiconductors are essential due to the existence of the p–n junction and a complementary metal oxide semiconductor (CMOS)-like circuit in organic electronic devices. Among various electron-deficient building blocks, imide-functionalized arenes, such as naphthalene diimide (NDI) and perylene diimide (PDI), have been proven to be the most promising ones for developing n-type organic and polymeric semiconductors. Nevertheless, phenyl-based NDI and PDI lead to sizable steric hindrance with neighboring (hetero)arenes and a high degree of backbone distortion in the resultant semiconductors, which greatly limits their microstructural ordering and charge transport. To attenuate the steric hindrance associated with NDI and PDI, a novel imide-functionalized heteroarene, bithiophene imide (BTI), was designed; however, the BTI-based semiconductors suffer from high-lying frontier molecular orbital (FMO) energy levels as a result of their electron-rich thiophene framework and monoimide group, which is detrimental to n-type performance. In this Account, we review a series of BTI derivatives developed via various strategies, including ring fusion, thiazole substitution, fluorination, cyanation, and chalcogen substitution, and elaborate the synthesis routes designed to overcome the synthesis challenges due to their high electron deficiency. After structural optimization, these BTI derivatives can not only retain the advantages of good solubility, a planar backbone, and small steric hindrance inherited from BTI but also have greatly suppressed FMO levels. These novel building blocks enable the construction of a great number of n-type organic and polymeric semiconductors, particularly acceptor–acceptor (or all-acceptor)-type polymers, with remarkable performance in various devices, including electron mobility (μe) of 3.71 cm2 V–1 s–1 in organic thin-film transistors (OTFTs), a power conversion efficiency (PCE) of 15.2% in all-polymer solar cells (all-PSCs), a PCE of 20.8% in inverted perovskite solar cells (PVSCs), electrical conductivity (σ) of 0.34 S cm–1 and a power factor (PF) of 1.52 μW m–1 K–2 in self-doped diradicals, and σ of 23.3 S cm–1 and a PF of ∼10 μW m–1 K–2 in molecularly n-doped polymers, all of which are among the best values in each type of device. The structure–property–device performance correlations of these n-type semiconductors are elucidated. The design strategy and synthesis of these novel BTI derivatives provide important information for developing highly electron-deficient building blocks with optimized physicochemical properties. Finally, we offer our insights into the further development of BTI derivatives and semiconductors built from them.
High-performance n-type (electron-transporting or n-channel) polymer semiconductors are critical components for the realization of various organic optoelectronic devices and complementary circuits, ...and recent progress has greatly advanced the performance of organic thin-film transistors, all-polymer solar cells, and organic thermoelectrics, to cite just a few. This Perspective focuses on the recent development of high-performance n-type polymer structures, particularly those based on the most investigated and novel electron-deficient building blocks, as well as summarizes the performance achieved in the above devices. In addition, this Perspective offers our insights into developing new electron-accepting building blocks and polymer design strategies, as well as discusses the challenges and opportunities in advancing n-type device performance.
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Challenges and opportunities:•Designing and synthesizing novel highly electron-deficient building blocks with very low-lying and delocalized lowest unoccupied molecular orbitals (LUMOs), reduced steric hindrance, and excellent solubilizing capability.•Developing facile polymerization methods that can effectively incorporate various electron-deficient building blocks into polymers. The n-type polymers have good solubility, a high content of acceptor units in polymeric backbones, optimized optoelectronic properties, high molecular weight, and minimal structural defects.•Achieving excellent n-type performance with robust stability in material processing and under device operation conditions.
n-Type (electron-transporting or n-channel) polymer semiconductors have been widely investigated for application in various organic optoelectronic devices. In this Perspective, we summarize the recent progress in electron-accepting building-block design and synthetic strategies for n-type polymers for realizing high-performance organic thin-film transistors, all-polymer solar cells, and organic thermoelectrics.
Imide‐Functionalized Polymer Semiconductors Sun, Huiliang; Wang, Lei; Wang, Yingfeng ...
Chemistry : a European journal,
January 2, 2019, Letnik:
25, Številka:
1
Journal Article
Recenzirano
Imide‐functionalized π‐conjugated polymer semiconductors have received a great deal of interest owing to their unique physicochemical properties and optoelectronic characteristics, including ...excellent solubility, highly planar backbones, widely tunable band gaps and energy levels of frontier molecular orbitals, and good film morphology. The organic electronics community has witnessed rapid expansion of the materials library and remarkable improvement in device performance recently. This review summarizes the development of imide‐functionalized polymer semiconductors as well as their device performance in organic thin‐film transistors and polymer solar cells, mainly achieved in the past three years. The materials mainly cover naphthalene diimide, perylene diimide, and bithiophene imide, and other imide‐based polymer semiconductors are also discussed. The perspective offers our insights for developing new imide‐functionalized building blocks and polymer semiconductors with optimized optoelectronic properties. We hope that this review will generate more research interest in the community to realize further improved device performance by developing new imide‐functionalized polymer semiconductors.
An engineering drive: Imide‐functionalized arenes are of particularly importance for constructing high‐performance semiconducting polymers owing to their unique combination of various device performance improving characteristics. The recent development of imide‐functionalized arenes and their polymer semiconductors has resulted in greatly improved device performance in both organic thin‐film transistors and polymer solar cells.
Modified 3,4‐ethylenedioxythiophene is employed as the conjugated side chain in conjugated polymers, which can significantly depress the dark current of the polymer photodetectors with little ...associated decrease in photovoltaic properties, thus enhanceing the detectivities. This approach can be applied to a variety of conjugated polymers covering a photoresponse range from UV to NIR.
High‐performance unipolar n‐type polymer semiconductors are critical for advancing the field of organic electronics, which relies on the design and synthesis of new electron‐deficient building blocks ...with good solubilizing capability, favorable geometry, and optimized electrical properties. Herein, two novel imide‐functionalized thiazoles, 5,5′‐bithiazole‐4,4′‐dicarboxyimide (BTzI) and 2,2′‐bithiazolothienyl‐4,4′,10,10′‐tetracarboxydiimide (DTzTI), are successfully synthesized. Single crystal analysis and physicochemical study reveal that DTzTI is an excellent building block for constructing all‐acceptor homopolymers, and the resulting polymer poly(2,2′‐bithiazolothienyl‐4,4′,10,10′‐tetracarboxydiimide) (PDTzTI) exhibits unipolar n‐type transport with a remarkable electron mobility (μe) of 1.61 cm2 V−1 s−1, low off‐currents (Ioff) of 10−10−10−11 A, and substantial current on/off ratios (Ion/Ioff) of 107−108 in organic thin‐film transistors. The all‐acceptor homopolymer shows distinctive advantages over prevailing n‐type donor−acceptor copolymers, which suffer from ambipolar transport with high Ioffs > 10−8 A and small Ion/Ioffs < 105. The results demonstrate that the all‐acceptor approach is superior to the donor−acceptor one, which results in unipolar electron transport with more ideal transistor performance characteristics.
Electron‐deficient thiazole imides are synthesized, which enables the development of all‐acceptor homopolymers. The polymer PDTzTI exhibits a remarkable electron mobility of 1.61 cm2 V−1 s−1 with minimal off‐currents of 10−10−10−11 A and substantial current on/off ratios of 107−108 in the saturation regime, thus showing distinct advantages over traditional donor−acceptor copolymers, which suffer from high off‐currents and small on/off ratios.
n-Type polymers with deep-positioned lowest unoccupied molecular orbital (LUMO) energy levels are essential for enabling n-type organic thin-film transistors (OTFTs) with high stability and n-type ...organic thermoelectrics (OTEs) with high doping efficiency and promising thermoelectric performance. Bithiophene imide (BTI) and its derivatives have been demonstrated as promising acceptor units for constructing high-performance n-type polymers. However, the electron-rich thiophene moiety in BTI leads to elevated LUMOs for the resultant polymers and hence limits their n-type performance and intrinsic stability. Herein, we addressed this issue by introducing strong electron-withdrawing cyano functionality on BTI and its derivatives. We have successfully overcome the synthetic challenges and developed a series of novel acceptor building blocks, CNI, CNTI, and CNDTI, which show substantially higher electron deficiencies than does BTI. On the basis of these novel building blocks, acceptor–acceptor type homopolymers and copolymers were successfully synthesized and featured greatly suppressed LUMOs (−3.64 to −4.11 eV) versus that (−3.48 eV) of the control polymer PBTI. Their deep-positioned LUMOs resulted in improved stability in OTFTs and more efficient n-doping in OTEs for the corresponding polymers with a highest electrical conductivity of 23.3 S cm–1 and a power factor of ∼10 μW m–1 K–2. The conductivity and power factor are among the highest values reported for solution-processed molecularly n-doped polymers. The new CNI, CNTI, and CNDTI offer a remarkable platform for constructing n-type polymers, and this study demonstrates that cyano-functionalization of BTI is a very effective strategy for developing polymers with deep-lying LUMOs for high-performance n-type organic electronic devices.
As a key component in perovskite solar cells (PVSCs), hole-transporting materials (HTMs) have been extensively explored and studied. Aiming to meet the requirements for future commercialization of ...PVSCs, HTMs which can enable excellent device performance with low cost and eco-friendly processability are urgently needed but rarely reported. In this work, a traditional anchoring group (2-cyanoacrylic acid) widely used in molecules for dye-sensitized solar cells is incorporated into donor–acceptor-type HTMs to afford MPA-BT-CA, which enables effective regulation of the frontier molecular orbital energy levels, interfacial modification of an ITO electrode, efficient defect passivation toward the perovskite layer, and more importantly alcohol solubility. Consequently, inverted PVSCs with this low-cost HTM exhibit excellent device performance with a remarkable power conversion efficiency (PCE) of 21.24% and good long-term stability in ambient conditions. More encouragingly, when processing MPA-BT-CA films with the green solvent ethanol, the corresponding PVSCs also deliver a substantial PCE as high as 20.52% with negligible hysteresis. Such molecular design of anchoring group-based materials represents great progress for developing efficient HTMs which combine the advantages of low cost, eco-friendly processability, and high performance. We believe that such design strategy will pave a new path for the exploration of highly efficient HTMs applicable to commercialization of PVSCs.
Realizing fully stretchable electronic materials is central to advancing new types of mechanically agile and skin-integrable optoelectronic device technologies. Here we demonstrate a materials design ...concept combining an organic semiconductor film with a honeycomb porous structure with biaxially prestretched platform that enables high-performance organic electrochemical transistors with a charge transport stability over 30-140% tensional strain, limited only by metal contact fatigue. The prestretched honeycomb semiconductor channel of donor-acceptor polymer poly(2,5-bis(2-octyldodecyl)-3,6-di(thiophen-2-yl)-2,5-diketo-pyrrolopyrrole-alt-2,5-bis(3-triethyleneglycoloxy-thiophen-2-yl) exhibits high ion uptake and completely stable electrochemical and mechanical properties over 1,500 redox cycles with 10
stretching cycles under 30% strain. Invariant electrocardiogram recording cycles and synapse responses under varying strains, along with mechanical finite element analysis, underscore that the present stretchable organic electrochemical transistor design strategy is suitable for diverse applications requiring stable signal output under deformation with low power dissipation and mechanical robustness.
Currently, n‐type acceptors in high‐performance all‐polymer solar cells (all‐PSCs) are dominated by imide‐functionalized polymers, which typically show medium bandgap. Herein, a novel narrow‐bandgap ...polymer, poly(5,6‐dicyano‐2,1,3‐benzothiadiazole‐alt‐indacenodithiophene) (DCNBT‐IDT), based on dicyanobenzothiadiazole without an imide group is reported. The strong electron‐withdrawing cyano functionality enables DCNBT‐IDT with n‐type character and, more importantly, alleviates the steric hindrance associated with typical imide groups. Compared to the benchmark poly(naphthalene diimide‐alt‐bithiophene) (N2200), DCNBT‐IDT shows a narrower bandgap (1.43 eV) with a much higher absorption coefficient (6.15 × 104 cm−1). Such properties are elusive for polymer acceptors to date, eradicating the drawbacks inherited in N2200 and other high‐performance polymer acceptors. When blended with a wide‐bandgap polymer donor, the DCNBT‐IDT‐based all‐PSCs achieve a remarkable power conversion efficiency of 8.32% with a small energy loss of 0.53 eV and a photoresponse of up to 870 nm. Such efficiency greatly outperforms those of N2200 (6.13%) and the naphthalene diimide (NDI)‐based analog NDI‐IDT (2.19%). This work breaks the long‐standing bottlenecks limiting materials innovation of n‐type polymers, which paves a new avenue for developing polymer acceptors with improved optoelectronic properties and heralds a brighter future of all‐PSCs.
Incorporating dicyanobenzothiadiazole into polymer yields an n‐type semiconductor DCNBT‐IDT, which exhibits a narrow bandgap of 1.43 eV and a high absorption coefficient of 6.15 × 104 cm−1. The DCNBT‐IDT‐based all‐polymer solar cells achieve a remarkable power conversion efficiency of 8.32% with a small energy loss of 0.53 eV and a photoresponse of up to 870 nm.
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