J.Y. Do*, B.G. Kim
aDepartment of Advanced Material for Information and Display, Pusan National University, Jangjeon-dong, Geumjeong-gu, Busan 609-735, Republic of Korea (email@example.com, http://jydo.campushomepage.com/)
Bulk hetero-junction photovoltaic cell was devised for better charge transporting property and easy processing using organic materials. Polymer blend made of P3HT and PCBM was recently announced to achieve energy conversion efficiency of about 5 %. Much work has been progressed with fullerene derivatives as an acceptor or hole transporting material owing to their unique electronic property. The morphology of blending film is seriously considered for the high conversion efficiency and sometimes controlled via thermal annealing. Oligothiophenes having repeating number of less than 10 can be accomplished with conventional synthetic methodologies and are beneficial for controlling film morphology and electronic properties depending on molecular structure. We designed a star-shaped oligothiophene which would make three-dimensional channels for better charge transportation. Oxadizole coupling reaction was introduced to interconnect two or three oligthiophenes. 1,3,5-Benzene-tricarbonyl chloride or 1,3-isophthalic chloride were heated with an oligothiophene terminated with a terazole unit. Oligothiophene was derived with alkyl substituents regio-regularly on 3-position of thiophene unit under the consideration of inerchain interaction of pi-conjugated thiophene as well as solvent solubility of resulting macromolecules. Physical and optical property of the prepared oligothiophenes will be presented along with electronic energy levels.