Traditional long-persistent luminescence (LPL) materials, which are based on inorganic systems containing rare elements and with preparation temperatures of at least 1000 °C, exhibit afterglow times of more than 10 h and can be tuned for different applications. However, the development of this field is hindered due to the large thermal energy consumption and the need for nonrenewable resources. Thus, the development of a "green" design and preparation of LPL materials is of some importance. A doped-crystalline material based on two metal-free organic small molecules is easily prepared through ultrasonic crystallization at room temperature. It has a high-quality, singlecrystalline structure, and visible LPL performance with a duration of more than 6 s upon low-energy photoexcitation. A green, flexible, and convenient screen-printing technology for controllable pattern anticounterfeiting is then developed from this purely organic material, which improves the prospects for commercial utilization in the future.
A h‐BN self‐aligned single‐crystal array (SASCA) that exhibits orderly alignment and uniformly distribution is controllably synthesized on a liquid Cu surface for the first time. The h‐BN SASCA exhibits highly accordant spatial orientation and homogenous domain size, which can realize highly integrated and individually switching field‐effect transistors when serving as a gate dielectric. Circular h‐BN single‐crystals, which are considered to be the building blocks of h‐BN SASCA, are also observed.
Anodization is a promising technique to form high- k dielectrics for low-power organic field-effect transistor (OFET) applications. However, the surface quality of the dielectric, which is mainly inherited from the metal electrode, can be improved further than other fabrication techniques, such as sol-gel. In this study, we applied the template stripping method to fabricate a low-power single-crystalline OFET based on the anodized AlO dielectric. We found that the template stripping method largely improves the surface roughness of the deposited Al and allows for the formation of a high-quality AlO high- k dielectric by anodization. The ultraflat AlO /SAM dielectric combined with a single-crystal 2,6-diphenylanthracene (DPA) semiconductor produced a nearly defect-free interface with a steep subthreshold swing (SS) of 66 mV/decade. The current device is a promising candidate for future ultralow-power applications. Other than metal deposition, template stripping could provide a general approach to improve thin-film quality for many other types of materials and processes.
The innovative design of sliding transfer based on a liquid substrate can succinctly transfer high‐quality, wafer‐size, and contamination‐free graphene within a few seconds. Moreover, it can be extended to transfer other 2D materials. The efficient sliding transfer approach can obtain high‐quality and large‐area graphene for fundamental research and industrial applications.
In recent years, exciting advances have been achieved in pursuing organic thin film transistors (OTFTs) with high mobility. Whereas, the economical infeasibility of Au source/drain (S/D) electrodes that are widely used in OTFTs hinders the further development of OTFTs in industry. In this study, the modified indium tin oxide (ITO) as S/D electrodes is adopted. The ITO is modified by HCl aqueous solutions, its surface work function is improved from 4.8 to 5.5 eV. By first‐principle calculations and experiments, the charge analysis shows that the Cl atom traps 0.475 electrons, which indicates that In–Cl dipoles are responsible for the increase of the surface work function, besides the HCl modification leads to In+‐Cl− bonds instead of In3+‐Cl− bonds on the ITO surface compared with the reported InCl3 modification. More encouragingly, In+‐Cl− surface is found to have higher Cl density, higher work function and higher conductivity. TIPS‐pentacene, with suitable HOMO level of 5.2 eV, is adopted as organic semiconductor, and the bar‐coating process is optimized to realize oriented films. OTFTs with maximum field‐effect mobility of 0.77 cm2 V−1 s−1 are achieved. The ITO electrodes modified by HCl can be promising in the industry.
Bottom‐gate and bottom‐contact n‐type and p‐type organic field‐effect transistors (OFETs) are simultaneously obtained by combining the ambipolar semiconductor film of diketopyrrolopyrrole‐based conjugated polymer (P4FTVT‐C32) with indium tin oxide (ITO) source/drain (S/D) electrodes. P4FTVT‐C32 thin film exhibits n‐type unipolar property with the low work functional (WF) ITO S/D electrodes modified by polyethylenimine ethoxylated (PEIE) and it exhibits p‐type unipolar property with the high WF ITO S/D electrodes modified by HCl:InCl3. Hence, complementary inverters with transition voltages near VDD/2 and the maximum gain of 138 converting “1” state input into “0” state output are achieved by two different modifications via screen printing on ITO electrodes and then, only one‐time bar coating of P4FTVT‐C32. To further improve the performance and the uniformity of the OFET devices, the modification of octadecyltrichlorosilane (OTS) is also introduced. This work provides an easy‐handling method for the fabrication of low‐cost, high performance organic electronic devices and integrated circuits.
The commercialization of organic thin film transistors (OTFTs) is partly hindered by the high cost and stubborn work function (WF) of common Au source/drain (S/D) electrodes. In this work, indium tin oxide (ITO) S/D electrodes modified with three different nitrogenous interlayers including 1,4‐bis(2‐hydroxyethyl) piperazine (HEP), polyethylenimine ethoxylated (PEIE), and branched polyethylenimine (PEI) are adopted to fabricate n‐type OTFTs. The WF of bare ITO is 4.7 eV, whereas ITO modified with nitrogenous interlayers exhibits WFs ranging from 4.1 to 3.6 eV. By the first‐principle calculation and element analysis, the protonated amines are critical for the reduction of ITO surface WF. Besides, the interlayers with higher nitrogen contents are more likely to improve the wettability of octadecyltrichlorosilane (OTS) modified ITO substrates, and help to gain the continuous and oriented poly[2,5‐bis(4‐tetradecyloctadecyl)pyrrolo[3,4‐c]pyrrole‐1,4(2H,5H)‐dione‐alt‐5,5′‐di(thiophen‐2‐yl)‐2,2′‐(E)‐1,2‐bis(3,4‐difluorothien‐2‐yl)‐ethene] (P4FTVT‐C32) semiconductor thin films. Therefore, P4FTVT‐C32 based OTFTs with maximum electron field‐effect mobility of 1.95 cm2 V−1 s−1 are achieved by PEI treatments. These results indicate that the ITO S/D electrodes modified by nitrogenous interlayers can greatly slash costs and promote commercialization of OTFTs.
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