Polycarbazole and polyfluorene containing cationic iridium(III) complexes in the side-chain have been designed and synthesized. Both polymers have been demonstrated to show conductance switching behavior and non-volatile flash memory devices based on them were successfully realized, in which the formation and dissociation of through-space charge-transfer states from the conjugated polymer “sea” to the Ir(III) complex “island”, controlled by voltage, are responsible for the conductance switching behavior and memory effect. The devices exhibit low reading, writing, and erasing voltages and a high ON/OFF current ratio. Both ON and OFF states are stable up to 107 read cycles at a read voltage of −1.0 V. Due to the different chemical structures of the polymer main-chain, the two devices show different threshold voltages. The polycarbazole derivative exhibits higher HOMO and LUMO levels compared with the polyfluorene analogue. Thus, the threshold voltage from the OFF to ON state of the device based on the polycarbazole derivative is obviously lower than that of the polyfluorene derivative-based device because of the low energy barrier between the work function of the ITO anode and the HOMO level of the polycarbazole derivative. Similarly, the threshold voltage from the ON to OFF state is evidently higher because the energy barrier of electron injection from Al into the LUMO of the polycarbazole derivative is slightly higher than that of the polyfluorene analogue. Thus, the threshold voltages of memory devices may be rationally modulated by modifying the chemical structure of polymers.
设计和合成了侧链含有阳离子
铱(III)配合物的聚
咔唑和聚
芴,两种聚合物均显示出导电开关行为,并成功实现了基于它们的非易失性闪存器件。在这些器件中,通过空间电荷转移状态的形成和解离,从共轭聚合物“海”到
铱(III)配合物“岛”,受电压控制,负责导电开关行为和存储效应。器件具有低读取、写入和擦除电压以及高开/关电流比。两种开和关状态在−1.0 V读取电压下稳定高达107次读取周期。由于聚合物主链的不同
化学结构,两种器件显示出不同的阈值电压。与聚
芴类似物相比,聚
咔唑衍
生物具有更高的HOMO和LUMO能级。因此,基于聚
咔唑衍
生物的器件从关到开状态的阈值电压明显低于基于聚
芴衍
生物的器件,因为ITO阳极功函数与聚
咔唑衍
生物HOMO能级之间的能量屏障较低。同样,从开到关状态的阈值电压明显较高,因为从铝注入到聚
咔唑衍
生物LUMO的电子注入能量屏障略高于聚
芴类似物。因此,通过修改聚合物的
化学结构,可以合理地调节存储器件的阈值电压。