Dip-coating Grown Ultra-thin Organic Film And Its Application

With the rapid development of organic electronics, organic semiconductor device become more and more important. The organic semiconductor thin film, as the core of an organic semiconductor device, has been drawn much concern. Up to date, the organic semiconductor device has put forward a higher requirement for organic thin film layer. The relationship between the chemical structure of organic molecules and the nature of the organic thin film is unclear. Therefore, design and synthesis of organic semiconductor molecules with specific functions, preparation for a controlled high quality organic semiconductor thin film to build an enhanced-performance organic optoelectronic device, and discovery for the relationship between the morphology and properties of organic semiconductor thin film is an important issue for organic electronics.Based on the above problems, we utilize DTBDT-Cn molecular as the research object and investigate their thin film property by dip-coating method. Our research was mainly conducted in the following three parts:1. We designed a series of organic semiconductor molecules with different alkyl chain length, DTBDT-Cn (n=4,6,9,12). A feasible synthetic schemes was made based on their specific molecular structure, followed with a necessary purification treatment and characterization of 1H-NMR and MS.’H-NMR and MS data indicated that we have successfully synthesized a given target molecule DTBDT-Cn (n=4,6,9,12) with high purity.2. We fabricated DTBDT-Cn series film through dip-coating method. A variety of characterization methods were used to tested film properties. From film morphology, structure and properties of the thin film transistor aspects, alkyl chain length and pull rate could obviously affect film properties. Thus the alkyl chain length could have an impact on molecular self-organization capabilities during dip-coating process. We found that alkyl chain length would directly affect DTBDT-Cn series film morphology, especially the thickness and orientation, and DTBDT-Cn series film packing structure. Under such research system, the molecule with hexyl group has stronger self-organization ability to form a controlled thickness, a clear orientation, high-quality crystalline thin film. Correspondingly top-contact thin film transistor was made based on DTBDT-Cn (n=4,6,9,12), while DTBDT-C6 has the highest mobility of 0.2 cm2/V·s, with the lowest threshold voltage and maximum Ion/off.3. The DTBDT-Cn series films with orientated, crystalline, controlled domains, were selected as molecular template layer to induce the crystalline growth of rubene thin film which usually form into amorphous film on inert substrate. Through deposition parameters regulation, annealing and prepared DTBDT-Cn, we successfully obtained rubrene crystalline films. The role of DTBDT-Cn inducing layer and the crystalline growth behavior were investigated and discussed.