The Study Of Organic Electronic Devices With Hetero-atom Materials

Organic semiconductor devices. such as light emitting diodes (OLEDs). organic solar cells. thin-film transistors, and electronic memories, have attracted much attention for their low cost, light weight, flexibility, and high performances. Compared with traditional inorganic semiconductor devices, organic semiconductor devices generally have relatively lower efficiency and stability. Many new materials were designed and prepared, aimed to improve the device performance. Among them, heteroatom-substituted materials are outstanding with spectacular optical and electronic properties. However, systematic investigation of device structure for this kind of new-emerged organic functional lags far behind. In this thesis, the optimized device structures of organic light-emitting diodes and memory devices for heteroatom-substituted materials were explored and discussed.1. The potentials of spin-coated MoO3as hole injection layer of OLED devices were investigated. With spin-coating process, the devices with configuration of ITO/HIL/NPB (60nm)/Alq3(60nm)/LiF (1nm)/Al (100nm) were fabricated. The device based on MoOj treated by hydrogen peroxide show good hole injection capability with the low turn-on voltage of2.8V and the maximum luminescence efficiency of2.91cd/A. The performance of the spin-coated MoO3devices are similar as that of devices prepared by evaporation of MoO3. indicating the potential of this treatment for OLEDs.2. The device structure for blue phosphorescent electroluminescent devices with bipolar organic materials of N-P structure was optimized. The devices with structure of ITO/MoO3(2nm)/m-M:MoO3(15wt%,30nm)/m-M(10nm)/Ir(ppz)3(10nm)/HOST:Firpic (10wt%,15nm)/Bphen(20nm)/LiF(1nm)/Al were prepared. To reduce the double beam interference effect, the ratio of guest material in light-emitting layer and the thickness of light-emitting layer and electron transport layer were optimized. And high performance of devices was obtained. Lower turn-on voltage of2.6V. higher current efficiency of32.3cd/A. higher power efficiency of37.2Im/W. and the largest external quantum efficiency of16.5%was observed along with stable EL spectra with color coordinates of (0.15.0.15).3. Based on the derivatives of PVK, i.e. polyvinyl methyl silafluorene (PSi). electrical bistable memory devices were fabricated with the structure of ITO/PSi/Al. The devices show excellent WORM type storage features with the switch ON/OFF ratio larger than106. To deep investigate the storage switch mechanism, the prepared devices with different organic layer thickness show different threshold voltage and switch ratios. Besides, we found that different annealing temperature only affects the threshold voltage. Based on the existing interpretation of PVK derivatives storage switch mechanisms, we suggest that the conductance state transitions are attributed to the molecular conformational changes during the operation of the memory device.