Conjugated polymers with cationic iridium(III) complexes in the side-chain for flash memory devices utilizing switchable through-space charge transfer
Conjugated polymers with cationic iridium(III) complexes in the side-chain for flash memory devices utilizing switchable through-space charge transfer
复制标题
侧链带有阳离子铱(III)配合物的共轭聚合物，用于利用可切换的空间电荷转移的闪存器件
DOI：
10.1039/c2jm31963b
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发表时间：
2012-11-21
影响因子：
--
通讯作者：
Huang, Wei
中科院分区：
文献类型：
--
作者：
Liu, Shu-Juan;Lin, Wen-Peng;Huang, Wei
设计并合成了侧链上含有Ir(III)阳离子的聚咔唑和聚荧烯配合物。这两种聚合物都表现出了电导开关行为，并成功地实现了基于它们的非挥发性闪存器件，其中，在电压的控制下，从共轭聚合物“SEA”到Ir(III)络合物“岛”的整个空间电荷转移态的形成和解离是导致电导开关行为和记忆效应的原因。该器件表现出低的读取、写入和擦除电压以及高的通断电流比。在−1.0V的读取电压下，开启和关闭状态都稳定在107个读取循环。由于聚合物主链的不同化学结构，两种器件表现出不同的阈值电压。与多荧衍生物相比，聚咔唑衍生物表现出更高的HOMO和LUMO水平。因此，由于ITO阳极的功函数和聚咔唑衍生物的HOMO能级之间的低能垒，基于聚咔唑衍生物的器件从关断到导通的阈值电压明显低于基于聚荧衍生物的器件。同样，从导通到关断的阈值电压明显较高，因为电子从铝注入到聚咔唑衍生物的LUMO中的能垒略高于聚荧烯类似物。因此，可以通过改变聚合物的化学结构来合理地调制存储器件的阈值电压。
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.