Optoelectronic Properties From Novel Organic Polymers

In recent years, great progress had been made in the field of organic electronics. Among which, devices based on organic materials for the application of energy source or display now catch more and more focus of research. Both organic photovoltaics (OPVs) and organic light emitting diodes (OLEDs) offer a low-cost in fabrication over a large area and also potential being made onto flexible substrates indicating a bright future in people's daily life.In this thesis, optoelectronic properties from two novel polymers poly(p-phenylene N-4-n-butylphenyl-N,N-bis-4-vinylenephenylamine) (PNB) and poly(p-phenylene N-4-n-butylphenyl-N,N-bis-4-cyanovinylenephenylamine) (PNP) will be investigated. Single layer structure ITO/PNB/Al and ITO/PNP/Al were prepared. Photovoltaic responses under a monochromatic illumination were observed, with an open circuit voltage of 0.3 V and 0.8 V. It was also discovered that the ITO/PNB/Al device showed a green electroluminescent emission at a forward bias with a turn-on voltage of about 6 V. The work demonstrated that the PNB material might possess dual exciton sites that resulted in a competition for excitons to be either separated or recombined. Both effects were associated with each other, which limited the photovoltaic or electroluminescence to some degrees.Double layer devices based on polymer PNB comprising small molecule material copper phthalocyanine (CuPc) or N,N'-ditridecylperylene-3,4,9,10-tetracarboxylic diimide (PTCDI-C13) as an additional layer were constructed for further investigation. While the HOMO and LUMO levels of the PNB material were estimated to be -5.18 eV and -2.75 eV, respectively, measured with cyclic voltammetry. The open circuit voltage of ITO/PNB/CuPc/Al,ITO/CuPc/PNB/Al,ITO/PNB/PTCDI-C13/Al were increased to 0.6 V, 0.8 V, and 0.4 V, respectively, hence the short circuit current was also improved in the double layer devices. In comparison of optical absorption and photocurrent spectra, it was demonstrated that the excitons could be separated and further generated carrier drifting to the opposite electrodes more efficiently in the double layer devices.