Synthesis And Properties Of Ambipolar Organic Semiconductors Based On Boron-nitrogen Coordination Bonds

Organic semiconductors are very important for organic electronics.They have been widely used as semiconducting materials in organic field-effect transistors?OFETs?.Organic semiconductors have shown unipolar?n-type or p-type?and ambipolar properties,and ambipolar organic semiconductors can transport both electrons and holes.Ambipolar organic semiconductors require suitable energy levels,namely,relatively low LUMO energy levels and high HOMO energy levels.However,it is very difficult to precisely tune the LUMO and HOMO energy levels simutaneously,resulting in the limited design strategies for ambipolar organic semiconductors.Till now,there are much less ambipolar organic semiconductors than p-type/n-type semiconductors.Moreover,ambipolar organic semiconductors usually show low and imbalanced charge-transporting ability.Therefore,the development of ambipolar organic semiconductor materials with high and balanced charge-transporting ability is a critical issue in organic electronics.This thesis focuses on the design and synthesis of ambipolar organic semiconductors with boron-nitrogen coordination bonds and the research results are shown bellow:1.We proposed the strategy of using boron-nitrogen coordination bonds?B?N?and oxygen/sulfur bridged non-conjugated structure to tune the LUMO and HOMO energy levels of organic semiconductors.We prepared two polyarenes?OBN/SBN?that contain four oxygen or sulfur atoms and two B?N units,respectively.The LUMO/HOMO energy levels of OBN and SBN are-3.52 e V/-5.56 e V and-3.67 e V/-5.77 e V respectively,which meet the requirements of ambipolar semiconductors.The OFET devices were prepared using solution-processing method.The hole and electron mobilities of OBN are 0.26 cm²V^-1s^-1 and 0.23 cm²V^-1s^-1,respectively,indicating its balanced and excellent ambipolar semiconducting properties.Results prove that our proposed strategy is effective for tuning of LUMO/HOMO energy levels of organic semiconductors.This work provides the new design ideas for ambipolar organic semiconductor materials.2.We developed three conjugated polyarenes with two boron-nitrogen coordination bonds at 1,3,1,6 and 1,8 positions.Through precisely designing the precursors,we efficiently synthesized there B?N-containing polyarene isomers.Owning to the B?N units at different positions,they exhibit significantly different optoelectronic properties.For example,in comparison to the 1,3-and 1,6-polyarenes,the 1,6-polyarene shows the significantly red-shifted absorption and fluorescence spectra.While the 1,3-and 1,8-polyarenes can transport both electrons and holes,the 1,6-polyarene only transports the holes.Therefore,the tuning of the positions of B?N units can effectively modulate the energy levels,electrochemical and photophysical properties,as well as semiconducting properties.This study provides a new approach for tuning the electron properties of organic semiconductors.