Fabricating nanoparticulate organic thin film transistor (OTFT) and organic photovoltaic (OPV) devices using inkjet printing

This thesis presents a systematic study on two types of semiconducting polymer nanoparticulate suspensions prepared using: (1) a surfactant-containing mini-emulsion method, and (2) a surfactant-free precipitation method. Both methods are performed in more environmentally friendly solvents compared with the harmful organic solvents used in conventional organic electronic device fabrication processes. The nanoparticle dispersions and thin films have been examined and characterised by the use of a combination of spectroscopic and microscopic techniques. Subsequently, the nanoparticles have been used to fabricate two types of organic electronic devices: (a) nanoparticulate organic thin film transistors (NPOTFTs) and (b) nanoparticulate organic photovoltaics (NPOPVs). For the NPOTFT fabrication, we have successfully produced low voltage solution-processible top gate NPOTFTs based on hygroscopic dielectrics using both surfactant-containing and surfactant-free P3HT nanoparticle suspensions. The nanoparticulate devices exhibited similar I-V characteristics to transistors based on P3HT films processed from organic solvent. We have also used P3HT:PCBM nanoparticles (prepared by the mini-emulsion and precipitation methods) to fabricate NPOPVs which also achieved a comparable device performance to conventional OPV devices processed in organic solvents. We present preliminary data showing, for the first time, the use of surfactant-free P3HT:PCBM nanoparticles in NPOPV devices. In addition, the application of surfactant-containing nanoparticles to produce for the first time preliminary proof-of-concept printed NPOTFTs and printed NPOPVs based on aqueous dispersion active layer using inkjet printing technique is also presented.