Organic thermoelectric (OTE) materials have attracted intensive attention because of their promising applications in flexible electricity generators and ultrathin solid cooling elements. The ...well-developed high mobility organic semiconductors (OSCs) are considered to be excellent candidates for high performance OTE materials. Although a variety of OSCs have been explored as OTE materials, their intrinsic potential has not been revealed owing to limited understanding of the structure–property relationship, an unsatisfied doping method, etc. In this perspective, we briefly review the requirements of OTE conversion and discuss the major strategies to develop high performance OTE materials from OSC candidates. We then introduce some achievements made with p- and n-type OSCs to provide a clear map of the development status. Finally, we detail our viewpoint of the opportunities and challenges in this cutting-edge field. We highlight that OSC-based TE study is an emerging topic in organic electronics and that there is a long way to go to get the true benefits of OTE materials.
Skin-like temperature- and pressure-sensing capabilities are essential features for the next generation of artificial intelligent products. Previous studies of e-skin and smart elements have focused ...on flexible pressure sensors, whereas the simultaneous and sensitive detection of temperature and pressure with a single device remains a challenge. Here we report developing flexible dual-parameter temperature-pressure sensors based on microstructure-frame-supported organic thermoelectric (MFSOTE) materials. The effective transduction of temperature and pressure stimuli into two independent electrical signals permits the instantaneous sensing of temperature and pressure with an accurate temperature resolution of <0.1 K and a high-pressure-sensing sensitivity of up to 28.9 kPa(-1). More importantly, these dual-parameter sensors can be self-powered with outstanding sensing performance. The excellent sensing properties of MFSOTE-based devices, together with their unique advantages of low cost and large-area fabrication, make MFSOTE materials possess promising applications in e-skin and health-monitoring elements.
Multi‐functional organic field‐effect transistors (OFETs), an emerging focus of organic optoelectronic devices, hold great potential for a variety of applications. This report introduces recent ...progress on multi‐functional OFETs including OFETs based sensors, phototransistors, light‐emitting transistors, memory cells, and magnetic field‐effect OFETs. Key strategies towards multi‐ functional integration of OFETs, which involves the exploration of functional materials, interfaces modifications, modulation of condensed structures, optimization of device geometry, and device integration, are summarized. Furthermore, remaining challenges and perspectives are discussed, giving a comprehensive overview of multi‐functional OFETs.
The utilization of organic devices as pressure-sensing elements in artificial intelligence and healthcare applications represents a fascinating opportunity for the next-generation electronic ...products. To satisfy the critical requirements of these promising applications, the low-cost construction of large-area ultra-sensitive organic pressure devices with outstanding flexibility is highly desired. Here we present flexible suspended gate organic thin-film transistors (SGOTFTs) as a model platform that enables ultra-sensitive pressure detection. More importantly, the unique device geometry of SGOTFTs allows the fine-tuning of their sensitivity by the suspended gate. An unprecedented sensitivity of 192 kPa(-1), a low limit-of-detection pressure of <0.5 Pa and a short response time of 10 ms were successfully realized, allowing the real-time detection of acoustic waves. These excellent sensing properties of SGOTFTs, together with their advantages of facile large-area fabrication and versatility in detecting various pressure signals, make SGOTFTs a powerful strategy for spatial pressure mapping in practical applications.
Construction of ultrathin film organic transistors is an important challenge towards deeper understanding of the charge transport mechanism and multifunctional applications. We report on precise ...thickness control of ultrathin films of several organic semiconductors by using a simple spin‐coating approach. Ultrathin film, n‐channel organic transistors with mobilities well over 1.0 cm2 V−1 s−1 have been realized and their potential in high‐sensitivity gas sensing and other applications is demonstrated.
We report the synthesis, characterization, and application of a novel series of diketopyrrolopyrrole (DPP)-containing quinoidal small molecules as highly efficient n-type organic semiconductors in ...thin film transistors (TFTs). The first two representatives of these species exhibit maximum electron mobility up to 0.55 cm2 V–1 s–1 with current on/current off (I on/I off) values of 106 for 1 by vapor evaporation, and 0.35 cm2 V–1 s–1 with I on/I off values of 105–106 for 2 by solution process in air, which is the first demonstration of DPP-based small molecules offering only electron transport characteristics in TFT devices. The results indicate that incorporation of a DPP moiety to construct quinoidal architecture is an effective approach to enhance the charge-transport capability.
Molecular doping of organic electronics has shown promise to sensitively modulate important device metrics. One critical challenge is the disruption of structure order upon doping of highly ...crystalline organic semiconductors, which significantly reduces the charge carrier mobility. This paper demonstrates a new method to achieve large modulation of charge carrier mobility via channel doping without disrupting the molecular ordering. Central to the method is the introduction of nanopores into the organic semiconductor thin films via a simple and robust templated meniscus‐guided coating method. Using this method, the charge carrier mobility of C8‐benzothieno3,2‐bbenzothiophene transistors is boosted by almost sevenfold. This paper further demonstrates enhanced electron transport by close to an order of magnitude in a diketopyrrolopyrrole‐based donor–acceptor polymer. Combining spectroscopic measurements, density functional theory calculations, and electrical characterizations, the doping mechanism is identified as partial‐charge‐transfer induced trap filling. The nanopores serve to enhance the dopant/organic semiconductor charge transfer reaction by exposing the π‐electrons to the pore wall.
Doping of organic electronics without disrupting molecular packing is a critical challenge preventing effective modulation of charge‐transport properties. Enhanced charge‐transfer doping in crystalline small‐molecule and polymer transistors is reported by introducing nanopores in organic semiconductors via meniscus‐guided coating. Nanopores lead to dramatic increase in charge‐carrier mobility by promoting charge transfer reaction across the pore wall.
Development of high‐performance organic thermoelectric (TE) materials is of vital importance for flexible power generation and solid‐cooling applications. Demonstrated here is the significant ...enhancement in TE performance of selenium‐substituted diketopyrrolopyrrole (DPP) derivatives. Along with strong intermolecular interactions and high Hall mobilities of 1.0–2.3 cm2 V−1 s−1 in doping‐states for polymers, PDPPSe‐12 exhibits a maximum power factor and ZT of up to 364 μW m−1 K−2 and 0.25, respectively. The performance is more than twice that of the sulfur‐based DPP derivative and represents the highest value for p‐type organic thermoelectric materials based on high‐mobility polymers. These results reveal that selenium substitution can serve as a powerful strategy towards rationally designed thermoelectric polymers with state‐of‐the‐art performances.
Packed in: A high‐performance p‐type organic thermoelectric material based on a selenium‐substituted diketopyrrolopyrrole (DPP) polymer was developed. With strong intermolecular interactions and ordered molecular packing, PDPPSe‐12 exhibits high Hall mobilities of 1.0–2.3 cm2 V−1 s−1 in doped states, yielding a maximum PF and ZT value of 364 μW m−1 K−2 and 0.25, respectively.
Three n-type polymers BDPPV, ClBDPPV, and FBDPPV which exhibit outstanding electrical conductivities when mixed with an n-type dopant, N-DMBI ...((4-(1,3-dimethyl-2,3-dihydro-1H-benzoimidazol-2-yl)phenyl)dimethylamine), in solution. High electron mobility and an efficient doping process endow FBDPPV with the highest electrical conductivities of 14 S cm–1 and power factors up to 28 μW m–1 K–2, which is the highest thermoelectric (TE) power factor that has been reported for solution processable n-type conjugated polymers. Our investigations reveal that introduction of halogen atoms to the polymer backbones has a dramatic influence on not only the electron mobilities but also the doping levels, both of which are critical to the electrical conductivities. This work suggests the significance of rational modification of polymer structures and opens the gate for applying the rapidly developed organic semiconductors with high carrier mobilities to thermoelectric field.
Structural defects in conjugated copolymers are severely detrimental to the optoelectronic properties and the performance of the resulting electronic devices fabricated from them. Therefore, the ...much-desired precision synthesis of conjugated copolymers with highly regular repeat units is important, but presents a significant challenge to synthetic materials chemists. To this end, aryl sulfides are naturally abundant substances and offer unrealized potential in cross-coupling reactions. Here we report an efficient room temperature polycondensation protocol which implements aryl disulfide C-S activation to produce defect-minimized semiconducting conjugated copolymers with broad scope and applicability. Thus, a broad series of arylstannanes and thioethers are employed via the present protocol to afford copolymers with number-average molecular weights (M
s) of 10.0-45.0 kDa. MALDI and NMR analysis of selected copolymers reveals minimal structural defects. Moreover, the polymer trap density here is smaller and the field effect mobility higher than that in the analogous polymer synthesized through thermal-activation Stille coupling.
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