Growth Of Air-stable And High Mobility N-type Organic Micro/Nanocrystal Arrays And Applications Of Optoelectronic Device

Recently, one-dimensional organic semiconductor materials have attracted by more and more researchers, owning to their special properties different from inorganic materials and widely used in optoelectronics field. Organic field-effect transistors(OFETs) is one of the most important applications of the materials, however, n-type organic semiconductor materials have some challenges remain to be worked out. Firstly, nchannel organic semiconductors are relatively rare, and most of them possess poor solubility. Secondly, carrier mobilities of the existing n-channel materials are very low in general, and most of them possess poor ambient stability. These challenges restricted the development of n-type OFETs, resulting less developed and far behind to their p-type counterparts. Furthermore, the application of large-scale integrated circuit need to fabricate large-area, high performance and air-stable n-type organic single crystal arrays. At present, there are a lot of reports about patterning p-type organic single crystals, but n-type are relatively rare. Thus, researches about fabricating large-area n-channel OFET device arrays are very urgent needed.This article focus on fabricating of n-type organic single crystal arrays and its optoelectronics devices application.Firstly, we improved the conventional dip-coating method. We through heating the solution to obviously improve the solubility and solution processability of organic single crystals, then dip-coating under high temperature to grow n-type organic single crystal arrays successfully. We fabricated bottom gate top contact OFET device, the single crystal ribbons show mobility as high as 2.33 cm2 V-1 s-1(with average mobility up to 0.97 cm2 V-1 s-1). Moreover, the devices show excellent air stability after exposing in air over 30 days. The mobility experiences 31.3 % degradation and the on/off ratio, threshold voltage kept almost unchanged. At last, we demonstrated the universality of this method to other materials with poor solubility. The selected compounds were fabricated into single crystal ribbon arrays successfully and showed excellent device performance. Our work facilitated the development of air-stable, n-channel OFETs and paved a new way towards the fabrication of high performance, organic nanostructure based integrated circuits.Secondly,in allusion to two problems exist in last work(nonuniform thickness of nanoribbons and difficult to grow large-scale nanoribbon arrays), we developed a simple yet efficient slope-coating method to solve these problems successfully. In this context, we selected BPE-PTCDI as target compound, then growing uniform, large-area n-type single crystal nanoribbon arrays successfully. Photoresist stripes serve as the template for the growth of nanoribbons, which not only guides the alignment of the resulting nanoribbons, but also manages their exact positions. Through using a slope to maintain the downstream flow and thus encourage the continuous growth of nanoribbons along photoresist stripes to avoid “coffee ring” effect. The width and thickness of nanoribbons can be finely tuned by the solution concentration and the slope angles. We fabricated bottom gate top contact OFET device, the single crystal ribbons show mobility as high as 2.89 cm2 V-1 s-1(with average mobility up to 1.27 cm2 V-1 s-1). Moreover, the devices show improved air stability after exposing in air over 50 days. A slight device performance decay(13 %) was observed with on/off current ratio kept almost unchanged after they were exposed in air for 50 days and the threshold voltage experienced a slight positive shift from 49 to 56 V. Finally, we integrated 5 × 5 pixels of nanoribbon array-based OFETs on substrate to demonstrate the uniform performance of the devices.Thirdly, we selected BPE-PTCDI as target compound, through using nonsolvent nucleation method to fabricate BPE-PTCDI microwires and researching its application in flexible photodetector. We used simple drop-casting method to fabricate microwire photodetector based on flexible substrate. The device has a broad-spectral response from the ultraviolet light regime to the visible light regime(302 nm-650 nm), exhibiting a high on/off switching ratio(larger than 200), high detectivity over 1011 Jones, competitive external quantum efficiency(EQE) and responsivity. At last, we studied the mechanical flexibility and electrical stability of the devices, the conductance of the device remained almost constant even after a hundred cycles of bending, and the electrical current nearly kept unchanged at different bending conditions. It is expected that single-crystalline microwire photodetectors will have important applications in future organic optoelectronic devices.