Joaquin Mogollon Santiana1,Adam Moule1,Meghna Jha1
University of California - Davis1
Joaquin Mogollon Santiana1,Adam Moule1,Meghna Jha1
University of California - Davis1
Semiconducting Polymers (SPs) have received widespread attention due to their promising<br/>qualities like superior absorbance/emission, easy chemical tunability, low-temperature solution<br/>processing, lightweight, and flexible substrates, and low environmental toxicity. A major obstacle to the development of SPs devices is the lack of patterning processes, most traditional lithography methods done for inorganic semiconductors damage the SPs. Recently the Moule group developed a process named Projection Photothermal Lithography (PPL) that enables patterning in SPs films based on solubility compatible with non-crosslinked polymers. The method works by placing a thin SP film inside a cell with a semi-poor solvent, a binary mixture of a strong and weak solvent that will not dissolve the film at room temperature but will spontaneously dissolve as the temperature rises. Light is projected onto an area which will generate heat. The local temperature will increase until it surpasses the dissolution temperature (DT) causing the polymer to dissolve allowing us to pattern the film. Previous work was done using P3HT where it was found that tunning the semi-poor solvent ratio had a direct relationship with the DT. Using PPL with a homemade microscope set up rapid (∼ 4cm<sup>2</sup>hr<sup>-1</sup>), large single exposure area (0.21 mm<sup>2</sup>), sub-μm patterns can be obtained optically In order to generalize this concept a different semiconducting polymer (PDPP3T) was used. It was determined that the PDI for this polymer is much broader than P3HT resulting in a significant difference in dissolution temperature for smaller and larger chains of polymers in the film. Knowing this our goal was to determine how PDI distribution and molecular weight affect the size of features made using the PPL method. With the PDPP3T data, it was determined that a larger molecular weight and small PDI are ideal for this patterning technique, as dissolution will occur more uniformly, which agrees with the P3HT results.