UC Davis

Semiconducting Polymers (SPs) are carbon-based (organic) semiconductors that have superior opto-electronic properties, mechanical flexibility, lower environmental toxicity, solution processability and compatibility with roll-to-roll processing. SPs can be used to fabricate typical organic devices like organic light emitting diodes, field effect transistors, electrochemical transistors, thermoelectrics and photovoltaics. Even though the future of organic semiconductor devices is bright, there is a need to improve opto-electronic performance for the era of miniaturization of electronic devices. The opto-electronic and solubility properties of a SP can be tuned via molecular doping. In my dissertation, I begin by discussing p-type molecular doping in SPs. I use a combination of UV-Vis-NIR spectroscopy, four-probe sheet resistance measurements, and X-ray absorption near-edge structure (XANES) spectroscopy to perform lifetime measurements to assess the stability of the FeCl3 doped polymers over time, which is crucial for evaluating the long-term performance and reliability of the doped films. Next, I explore photothermal patterning as a promising patterning technique that leverages the solubility characteristics of SPs. I demonstrate the rapid adaptability of this technique using one of the commercially available direct-write photolithography apparatus, the Alvéole PRIMO that is commonly found in university clean rooms. I also develop a predictive model to quantify photothermal dissolution of SPs in solvent mixtures. Lastly, I present solution processable and tunable red/NIR narrow-band organic photodetectors (OPDs). I use the combined strategy of exciton dissociation narrowing and layer solubility to achieve narrow-band OPDs with a built-in filter and a planar heterojunction. By changing the thickness of the total optical cavity, I was able to obtain a peak response at 721 nm with a responsivity of 0.012 A/W, an EQE of 2 % and a FWHM of ∼85 nm and shift this peak response between red and NIR light.