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Vertical organic field-effect transistors (VOFETs) have been explored with a higher current density, a faster switch speed, and a better air stability than conventional OFETs, which dramatically enhance the capability of driving an AMOLED backplane. Unfortunately, the state-of-the-art of the fabrication of solution-processed VOFETs is still very complicated, which can only focus at a single-cell level. In this work, with the assistance of the inkjet print, the fabrication process of a solution-processed VOFET was significantly simplified, and a solution-processed VOFET array was fabricated for the first time, which exhibited excellent device performance and outstanding mechanical stability. More importantly, the VOFET arrays exhibited excellent photodetector properties, and a flexible image sensor based on VOFET arrays with multipoint visible photodetection and image recognition was demonstrated for the first time. Therefore, this novel process dramatically simplified the VOFET device fabrication process and a successfully realized array, which promoted the commercialization of VOFET and showed great potential in flexible display, multifunctional sensors, and wearable integrated circuits.

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Organic phototransistors with high responsivity and sensitivity to light irradiance have great potential applications in environmental monitoring, space exploration, security, image sensors and healthcare systems. In this manuscript, a novel polymer bulk heterojunction field effect phototransistor with ultrashort channel length (tens of nanometers) and ultrahigh sensitivity to visible light was proposed. Due to the nanoscale channel and bulk heterojunction structure, a high-performance phototransistor with high responsivity of 750 A/W, photosensitivity of 1.0 × 10 6 , and detectivity as high as 4.54 × 10 15 Jones was demonstrated under 720 nm light illumination with 0.1 mW/cm 2 intensity, which was even better that those lateral organic phototransistors. Moreover, organic phototransistors with ultrashort channel length were investigated for the first time on a flexible substrate, which exhibited outstanding mechanical flexibility due to their unique designs. Further investigation of the correlation between the morphology of bulk heterojunction blends and the device photoresponse performance indicated that the photoelectric properties of the devices could be effectively enhanced by controlling the morphology of semiconducting layers. More importantly, this work provided first clear experimental evidence that the surface area of semiconducting crystals would significantly impact dissociation of photoinduced excitons and transfer and recombination of photogenerated carriers, which is crucial for photoelectric performance of phototransistors. This work provided critical guidelines for the development of high performance flexible organic phototransistors, which opened up the doors of opportunity for organic phototransistors applications in a wide range of organic electronics.

Depending on the storage mechanisms, organic field-effect transistor (OFET) memory is usually divided into floating gate memory, ferroelectric memory, and polymer-electret-based memory. In this work, a new type of nonvolatile OFET memory is proposed by simply blending a p-type semiconductor and a n-type semiconductor without using an extra trapping layer. The results show that the memory window can be effectively modulated by the dopant concentration of the n-type semiconductor. With the addition of a 5% n-type semiconductor, blending devices exhibit a large memory window up to 57.7 V, an ON/OFF current ratio (I ON/I OFF) ≈ 105, and a charge retention time of over 10 years, which is comparable or even better than those of most of the traditional OFET memories. The discontinuous n-type semiconductor is set as a charge-trapping center for charge storage due to the quantum well-like organic heterojunctions. The generalization of this method is also investigated in other organic systems. Moreover, the blend devices are also applied to optical memory and show multilevel optical storage, which are further scaled up to 8 × 8 array to map up two-dimensional (2D) optical images with long-term retention and reprogramming characteristic. The results reveal that the novel system design has great potential application in the field of digital image memory and photoelectronic system.