Highly crystalline,highly stable n-type ultrathin crystalline films enabled by solution blending strategy toward organic single-crystal electronics

The development of n-type semiconductor is still far behind that of p-type semiconductor on account of the challenges in enhancing carrier mobility and environmental stability.Herein,by blending with the polymers,n-type ultrathin crystalline thin film was successfully prepared by the method of meniscus-guided coating.Remarkably,the n-type crystalline films exhibit ultrathin thickness as low as 5 nm and excellent mobility of 1.58 cm^(2) V^(-1) s^(-1),which is outstanding in currently reported organic n-type transistors.Moreover,the PS layer provides a high-quality interface with ultralow defect which has strong resistance to external interference with excellent long-term stability,paving the way for the application of n-type transistors in logic circuits.

表面自由能对二维结晶的影响

二维分子晶体是一类具有优异光电性能的新兴材料.然而,由于人们对决定二维结晶的因素知之甚少,二维分子晶体的生长极具挑战.我们研究了有机半导体的二维结晶和表面自由能之间的关系,提出了利用表面自由能各向异性因子来衡量二维结晶趋势的设想.以两个BTBT衍生物为例,我们发现具有大的g因子的分子有不受外界条件干扰的二维结晶趋势.这项工作为合理设计可二维结晶的有机半导体提供了指导.

Cocrystal engineering:towards high-performance near-infrared organic phototransistors based on donor-acceptor charge transfer cocrystals

Near-infrared organic phototransistors have wide application prospects in many fields.The active materials with the high mobility and near-infrared response are critical to building high-performance near-infrared organic phototransistors,which are scarce at present.Herein,a new charge transfer cocrystal using 5,7-dihydroindolo[2,3-b]carbazole(5,7-ICZ)as the donor and 2,2’-(benzo[1,2-b:4,5-b’]dithiophene-4,8-diylidene)dimalononitrile(DTTCNQ)as the acceptor is properly designed and prepared in a stoichiometric ratio(D:A=1:1),which not only displays a high electron mobility of 0.15 cm^(2)V^(-1)s^(-1) and very low dark current,but also can serve as the active layer materials in the region of near-infrared detection due to the narrowed band gap and good charge transport properties.A high photosensitivity of 1.8×10^(4),the ultrahigh photoresponsivity of 2,923 A W-1and the high detectivity of 4.26×10^(11)Jones of the organic near-infrared phototransistors are obtained.

Low-power high-mobility organic single-crystal field-effect transistor

Evolving flexible electronics requires the development of high-mobility and low-power organic field-effect transistors(OFETs)that are crucial for emerging displays,sensors,and label technologies.Among diverse materials,polymer gate dielectrics and two-dimensional(2D)organic crystals have intrinsic flexibility and natural compatibility with each other for OFETs with high performance;however,their combination lacks non-impurity and non-damage construction strategies.In this study,we developed a desirable OFET system using damage-free transfer of 2D organic single crystal,dinaphtho[2,3-b:2',3'-f]thieno[3,2-b]thiophene on a unique polymer dielectric layer,poly(amic acid)(PAA).Benefiting from the unique PAA surface nanostructure and the long-range ordered characteristics of the 2D organic single crystal,the resulting OFETs show remarkable performance with high mobility and low operating voltage of 18.7 cm^(2) V^(−1) s^(−1) and−3 V,respectively.The result indicates that combining polymer gate dielectric with 2D organic single crystal using a high-quality method can produce flexible electronic devices with high performance.

Vertical‐organic‐nanocrystal‐arrays for crossbar memristors with tuning switching dynamics toward neuromorphic computing

Memristors proposed by Leon Chua provide a new type of memory device for novel neuromorphic computing applications.However,the approaching of distinct multi‐intermediate states for tunable switching dynamics,the con-trolling of conducting filaments(CFs)toward high device repeatability and reproducibility,and the ability for large‐scale preparation devices,remain full of challenges.Here,we show that vertical‐organic‐nanocrystal‐arrays(VONAs)could make a way toward the challenges.The perfect one‐dimensional structure of the VONAs could confine the CFs accurately with fine‐tune resistance states in a broad range of 103 ratios.The availability of large‐area VONAs makes the fabrication of large‐area crossbar memristor arrays facilely,and the analog switching characteristic of the memristors is to effectively imitate different kinds of synaptic plasticity,indicating their great potential in future applications.

Few-layered organic single-crystalline heterojunctions for high-performance phototransistors

Photogating and electrical gating are key physical mechanisms in organic phototransistors(OPTs).However,most OPTs are based on thick and polycrystalline films,which leads to substantially low efficiency of both photogating and electrical gating and thus reduced photoresponse.Herein,high-performance OPTs based on few-layered organic single-crystalline heterojunctions are proposed and the obstacle of thick and polycrystalline films for photodetection is overcome.Because of the molecular scale thickness of the type I organic single-crystalline heterojunctions in OPTs,both photogating and electrical gating are highly efficient.By synergy of efficient photogating and electrical gating,key figures of merit of OPTs reach the highest among those based on planar heterojunctions so far as we know.The production of few-layered organic single-crystalline heterojunctions will provide a new type of advanced materials for various applications.

Ligand effects on electronic and optoelectronic properties of two-dimensional PbS necking percolative superlattices

The inter-nanocrystal （NC） distance, necking degree, ordering level, and NC surface ligands all affect the electronic and optoelectronic properties of NC solids. Herein, we introduce a unique PbS structure of necking percolative superlattices to exclude the morphological factors and study the effect of ligands on the NC properties. X-ray photoelectron spectroscopy data indicate that 1,2-ethanedithiol （EDT）, oxalic acid, mercaptopropionic acid, and NH4SCN （SCN） ligands were attached to the surface of NCs by substrate-supported Iigand exchange. Field-effect transistors were tested and photodetector measurements were performed to compare these NC solids. An SCN-treated film had the highest mobility and responsivity under high-power intensity irradiation owing to its high carrier density, whereas an EDT-treated film had the lowest mobility, photocurrent, and dark current. These findings introduce new avenues for choosing suitable ligands for NC applications.

Cocrystal engineering: Tuning the charge transfer excitons for highly sensitive luminescent switching materials under multiple stimuli

This paper presents a multi-stimuli responsive cocrystal system with luminescent properties that can be dynamically controlled and demonstrates the responsive mechanism of cocrystals under multiple stimuli(acid/alkali vapor, force, and heat). Detailed spectroscopic, computational, and structural studies exhibit that obvious charge transfer interactions occur in loosely mixed-stacking cocrystals. Such interactions can be weakened by acid vapor fuming due to the strong electron-withdrawing effect of acid cations and strengthened under mechanical grinding. Furthermore,the response time of the cocrystal is in the order of seconds,which is much superior to those of most previously reported stimuli-responsive cocrystals. Accordingly, a high-sensitive fluorescence switching is demonstrated under multiple stimuli, providing an effective strategy to develop smart materials.

Efficient energy transfer in organic light-emitting transistor with tunable wavelength

Key challenges in the development of organic light-emitting transistors(OLETs)are blocking both scientific research and practical applications of these devices,e.g.,the absence of high-mobility emissive organic semiconductor materials,low device efficiency,and color tunability.Here,we report a novel device configuration called the energy transfer organic light-emitting transistor(ET-OLET)that is intended to overcome these challenges.An organic fluorescent dye-doped polymethyl methacrylate(PMMA)layer is inserted below the conventional high-mobility organic semiconductor layer in a single-component OLET to separate the functions of the charge transport and light-emitting layers,thus making the challenge to essentially integrate the high mobility and emissive functions within a single organic semiconductor in a conventional OLET or multilayer OLET unnecessary.In this architecture,there is little change in mobility,but the external quantum efficiency(EQE)of the ET-OLET is more than six times that of the conventional OLET because of the efficient Förster resonance energy transfer,which avoids exciton-charge annihilation.In addition,the emission color can be tuned from blue to white to green-yellow using the sourcedrain and gate voltages.The proposed structure is promising for use with electrically pumped organic lasers.