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Organic photodiodes (OPD) are becoming promising candidates for narrowband detection to meet new requirements on detectors, such as smaller size, higher resolution, lower power consumption, and the ability to interact with a variety of interfaces. In this article, a new narrowband green-light sensitive squarylium material with donor–acceptor–donor structure and its application in photodiode are reported. Due to the material with intense and sharp absorption in the green color and simple single-layer structure, the device shows excellent color selectivity. The green EQE of the device reaches 66%, while the blue EQE is as low as 10%. The device also shows significantly low dark current of ∼5.4 nA·cm–2 at −2.5 V and high specific detectivity of 7.7 × 1012 Jones. The strategy for designing narrowband OPD can be extended to other wavelength region by replacing substituent group in the donor–acceptor–donor structure of the squarylium and using the single-layer structure.

of researchers because of its higher carrier mobility in solution fabricated OFET devices. [5,6] Anthopoulos introduced a method for blending C8-BTBT with a polymer, achieving a mobility of 13 cm 2 V −1 s −1 , while Minemawari et al. reported that the C8-BTBT carrier mobility could reach 16.4 cm 2 V −1 s −1 by applying the inkjet printing process. [7,8] Bao and co-workers reported C8-BTBT transistors with an ultrahigh carrier mobility of 43 cm 2 V −1 s −1 , which were produced by off-center spin coating. [6] Wang et al. used the airflow method to fabricate C8-BTBT single crystalline layers and transistors with average and maximum mobilities of 4.8 and 13.0 cm 2 V −1 s −1 , respectively. [9] Nonetheless, the fabrication methods proposed until now still present the drawbacks of being complex and of producing films characterized by an insufficient mobility and low uniformity when to be applied to large-area substrates. Therefore, new methods for OFETs production still need to be developed.In a previous work, our group achieved the production of highly oriented 6,13-bis(triisopropylsilylethynyl) pentacene crystalline thin films by the Marangoni effect-controlled oriented growth (MOG). [10] The MOG method combines the advantages of the "Coffee ring" and Marangoni effects, including highly oriented film deposition, capability of fabricating high surface area films, and low fabrication times. In this work, the MOG method is extended to the fabrication of a C8-BTBT thin film. The substrate is dipped into a mixture solution of C8-BTBT in methylbenzene and carbon tetrachloride and then lifted from the liquid. With the evaporation of the solvent, the "coffee ring" effect makes C8-BTBT particles deposit on the upper edge of the substrate, while the Marangoni effect causes a movement of the C8-BTBT particle away from the upper edge (Figure 1). The balance of these two effects favors the production of a uniform C8-BTBT film on the substrate during the evaporation of the solution. The produced C8-BTBT film is oriented and uniformly covers the substrate.In our experiments, a glass/indium tin oxide (ITO)/AlO x substrate is used. The choice was made because that AlO x can act as the dielectric gate and is capable of adsorbing the alkyl solution, which is favoring the optimal arrangement of the C8-BTBT molecules based on the MOG method. [11][12][13] Grazing-incidence X-ray diffraction (GIXRD) and transmission electron microscopy (TEM) were applied to find that the produced C8-BTBT film was highly oriented. The OFETs based on this C8-BTBT Highly oriented organic semiconductors have the advantages of relative low trap density and high carrier mobility. These features make organic transistors valuable in many commercial fields, such as electronic sensor arrays and flexible circuits. Here a simple and efficient "Marangoni effect-controlled growth" method is introduced to fabricate highly oriented 2,7-dioctyl[1] benzothieno[3,2-b][1]benzothiophene (C8-BTBT) films on AlO x substrates. The oriented film can cover nearly 60% of the substra...

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