The Growth And Photoelectric Properties Of Organic Crystals Modified By Polymers Based On Solution-processing

Rubrene receives extensive attention by researchers due to its excellent fluorescence and semiconductor properties of good electrical conductivity and high absorption coefficient.However,the film-forming property of rubrene molecule is poor and its crystallization process is difficult to control.This dissertation attempts to solve this problem by using polyvinyl pyrrolidone?PVP?or poly styrene?PS?as interface modification layer on the Si/SiO₂ substrate to induce crystallization of rubrene.The effect of interfacial modification layers,polymer concentration and film-forming temperatures on rubrene crystals are studied.Large-area continuous rubrene crystalline thin film with high crystallinity are prepared.The morphology and crystal structures of crystalline rubrene thin film with PVP or PS interface modification layer are analyzed by AFM,POM,SEM and TEM.And the growth mechanism of rubrene films on the PVP or PS interface modification layer is proposed.The results show that PVP or PS used as interface modification layer can promote the crystallization of rubrene thin film.Low concentration of PVP or PS and the appropriate film-forming temperature are beneficial to prepare large-area continuous spherulites,which formed by close arrangement of smaller branched crystals.Rubrene thin film modified by PVP interface modification layer shows a remarkable ohmic characteristic.The current increases with the increase of voltage within a certain range.The current switch ratio of rubrene crystalline thin film transistor with PS as interface modification layer is 10⁵.And this thin film transistor has good light sensitivity with fast response speed,high repeatability and good stability.Under the simulated sunlight illumination of 200 mW/cm²,the photoresponsivity of it can up to 4.7?A/W,and the photocurrent/dark-current ratio up to10³.