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It is generally believed that the incorporation of fluorine functional groups into dielectrics can effectively impede the charge‐trapping process and improve carrier mobility. However, the relationship between the device performance and fluorinated groups is still not clear and also the modulation effect of fluorine functional groups on photogenerated charge carrier in phototransistors has not yet been investigated. Herein, phototransistors are constructed by using three kinds of gate dielectric layers with different fluorinated groups to exploit the effect of fluorine functional groups. It is concluded that the presence of fluorinated groups indeed increases the transistor mobility and optical figures of merit in phototransistors compared to the device with a fluorine‐free dielectric layer. Concurrently, the exciton binding energy is increased with the addition of fluorinated groups, resulting in the decrease of phototransistor performance compared with less content of fluorinated groups due to the synergistic balance effect of fluorine functional groups. The results further clarify how the fluorine functional groups optimize the interface of organic phototransistors and modulate the photoelectric performance. [ABSTRACT FROM AUTHOR]

Organic phototransistors (OPTs) are playing an indispensable role in organic optoelectronics, which greatly show their promising application in optical communication, video imaging, missile guidance, and night vision. However, because the thermally activated mode dominated for thin‐film devices leads to a sharp drop in mobility at low temperatures, until now, most of the studies about OPTs are performed at room temperature, severely hindering their further potential optoelectronic application over a broad range of temperatures, especially at low temperature environment. In this work, the optoelectronic properties of a small molecule (2,6‐diphenylanthracene, DPA) based OPTs with band‐like transport are studied at low temperatures. The devices exhibit outstanding optoelectronic properties in terms of mobility (2.6 cm2 V−1 s−1), on/off ratio (≈104), detectivity (1013 Jones), and external quantum efficiency (2500%) even at 150 K, which is superior to the performance of devices with thermally activated mode. In addition, the organic photodetector at low temperatures is also fabricated. Our results demonstrate that organic π‐conjugated DPA small‐molecule has great potential in low‐temperature application. [ABSTRACT FROM AUTHOR]

Composite gratings play important roles in modern information technology. However, such gratings are generally based on the same structural pattern with limited types, and their structural parameters are difficult to tune, which greatly limit their application. A mechanically tunable composite grating in bilayer film, which orthogonally couples a sinusoidal phase grating and a rectangular phase grating, is developed here. The structural parameters of the grating can be well tuned by mechanically stretching or releasing the grating in the uniaxial direction. Naturally, this property allows tunable light manipulation: that is, a single incident laser beam can be split into a 2D diffraction beams array, and the intensity and propagation angle of each diffraction beam can be precisely controlled via mechanical manipulation of the grating. A theoretical model based on scalar diffraction theory that can quantitatively describe and accurately predict this light manipulation is further established. In addition, after treatment with an electron beam, the tunable structures can be immobilized, which enables the storage of information in the bilayer film. This work may open up new pathways for composite grating fabrication and further extend the applications of composite gratings in diverse fields. A composite grating orthogonally coupling a sinusoidal and a rectangular phase grating is created in a bilayer film. This pattern can be well tuned under mechanical manipulation, and it allows tunable light manipulation behavior. Under additional irradiation treatment, the tunable pattern can be immobilized, which allows one to store information into this bilayer film as well as to prepare a rigid grating on a compliant substrate. [ABSTRACT FROM AUTHOR]