Coating engineering of composite materials for organic field-effect transitors
- Authors
- Del Pozo Le?n, Freddy Geovanny
- Format
- DoctoralThesis
- Status
- publishedVersion
- Description
This thesis describes the development of a technology to deposit thin films of insulating polymers and composite materials for applications in organic field-effect transitors (OFETs). Composite materials are comprised of a semiconductor and an insulator. The insulator is the binder and the semiconductor the active material. The active materials are either polymers or small molecules. Binders are styrenes, methacrylates or combinations of both. In order to first demonstrate the capabilities of the technology developed, namely Bar Assisted Meniscus Sheering (BAMs), thin films of polystyrene on Si/SiOx were deposited, typical thicknesses in the range of 50 to 80 nm were found, also RMS values in the range of 0.5-0.6 nm were found as well, and confirms very smooth films with tentative application as dielectrics. Poly-(3 hexilthiophene) (P3HT) is widely used is organic field-effect transistors. Composite materials comprised of P3HT and polystyrene were tested. OFETs fabricated based on composites which only use a 10% of the active material exhibited a mobility of 0.1 cm2V-1s-1 such value match the maximum mobility value reported in literature to-date for pure P3HT. It is important to highlight that all OFETs fabricated by BAMS using based on the composites have threshold voltages around zero volts despite the fact that all fabrication and characterization were carried out in air. Polymeric semiconductors plays a very important role inside organic semiconductors, due to their advantage the processability. On the other hand, small-molecules lacks processability but in general possess high mobility than polymeric semiconductors. So, composite materials were devised to add processability to small-molecules, but trying to maintain high mobility. TTF derivatives, dibenzo-tetrathiafulvalene (BET-TTF) were the three small-molecules investigated. First, thermally evaporated films of pure DB-TTF and BET-TTF were investigated and their stability in air assessed, found that both are extremely unstable under the presence of oxygen and water even at ppm levels. The inclusion of BAMs have been proven effective in order to produce OFETs based on composites-insultor binder and TTF-derivatives. First, poly PAMS, and DB-TTF composites were investigated. OFETs fabricated shows stability in air and text-book like output and transfer characteristics, all with acceptable mobilities in the range of 10?3 cm 2V-1 S-1. Also OFETs based on isotactic polystyrene and DB-TTF were investigated reporting mobilities in the range of 10 -2 cm 2 V-1 S-1. Further, and creening of compositions for composites were carried out varying blend contact devices.
- Publication Year
- 2014
- Language
- eng
- Topic
- NANOTECNOLOG?A
F?SICA APLICADA
COMPOSITE MATERIALS
ORGANIC FIELD
- Repository
- Repositorio SENESCYT
- Rights
- openAccess
- License