The Preparation, Optoelectronic Properties And Memory Devices Of Cyano Functional Bulky Spiro-fluorene Organic Semiconductor

In recent years, considering the unique cruciformed spiro-arene has a serials advantage as the special steric hindrance, controllable electronic structure and stable morphology. Herein, it has been widely researched in organic electroluminescent, organic solar cells and organic storage and so on. In this article, the spiro-fluorene compounds are functionalized to investigate the relationship between molecular structure and device performance.Firstly, a serial of cyano substitute spiro-fluorene are designed and synesized by using spiro[fluorene-9,9’-xanthene](SFX) as building block which we have reported in the year of 2006. And the systematical study has been taken to study their electrochemical properties, electronic structure and the formation of exciplex. According to the results of experiment, it reveals that symmetrical cyano substitude spiro-fluorene can form the exciplex when combining it with appropriate donor material. The exciplex can realize long fluorescence lifetime, high fluorescence quantum efficiency and even improve the device efficiency based on SFXs.Secondly, the dipole moments of SFXs are characterized by their crystallography data, electrostatic potential(ESP) calculation, UV-Vis absorption and photoluminescence. Then, the cyano substituted SFXs are introduced into transistor menmory as organic charge storage elements(OCSEs) to investigate the relationship between dipole moments of SFXs and their charge trapping abilities. By comparing the memory window, charge storage density and charge trapping rate, we conclude that the weaker dipole moments of SFXs, rather than that of stronger one, exhibit excellent hole trap ability. And the electrical write and photo erasing type non-volatile transistors memory are obtained by exposing the devices under LED light.Lastly, by comparing the electronic structure, ESP and dipole moment of larger π-system spiro[fluorene-9,9’- dibenzoxanthene](SFDBXs), we find that dipole moments of bulky SFDBXs are smaller than those SFXs. In order to investigate the steric hindrance effect of SFDBXs based transistor memory, the memory windows of them are contrasted and the results show the bulky SFDBXs can help generate more hole trapping center and even achieve high density electric storage devices.