Ambipolar Organic Field Effect Transistor Memory Based on H-Type Fluorene-Based Small Molecule

Abstract

A small organic molecule 3Ph-TrH with a rigid structure was designed with π-bridge thienyl and fluorenyl groups as hole trapping sites and the fluorenyl and phenyl units as electron trapping sites according to steric hindrance. Then, the floating gate type organic field-effect transistor (OFET) memories based on this small organic molecule through solution processing were fabricated. The experimental results show that there is a hole storage window of 31.2 V and an electron storage window of 11.6 V in this device, exhibiting ambipolar charge storage based on a single small molecule material. To improve the stability of the device, a floating-gate OFET memory based on 3Ph-TrH with polystyrene (PS)-doped film was further prepared. The test results show that the device is equipped with better device stability and tolerance than those based on 3Ph-TrH as a single-component charge trapping layer. After 10000 s of retention times test, ON/OFF current ratio of the device can still be maintained at 1.1×10 3 , only reduced by an order of magnitude. This work can provide an idea for the preparation of a new type of OFET memory with ambipolar storage. Keywords steric hindrance; fluorene-based small molecule material; charge trapping layer; ambipolar charge storage; floating gate type organic field-effect transistor (OFET) memory 1 引言 有机场效应晶体管(OFET)存储器由于其低成本、 易 加工、高密度信息存储、非破坏性读取、易与电路集成 等诸多优点 [1][2][3][4][5][6] , 得到广泛关注. 其中, 通过电荷捕获层 对电荷的俘获与释放实现对信息存储的 OFET 存储器, 成为近年来的研究热点之一 [7][8][9][10] . 目前, 可以充当电荷 捕获层的材料可以大体将其分为三类: 有机小分子材 料 [3] 、聚合物材料 [11] 、无机材料 [12] . 这当中有机小分子 材料因具有分子量可控、合成步骤简易、易于纯化等优 势, 而受到研究者的青睐 [10,[13][14] . 但目前大部分已报道 的小分子表现出单极性存储 [3] , 只有少数可以通过单一 小分子组分实现双极性电荷存储 [15][16][17] . 2018 年, 解令海 课题组 [18] 报道了基于 D-A 型小分子 TPA(PDAF) 3 单组分 的 OFET 存储器, 其中三苯胺和位阻型氮杂芴单元分别 作为空穴和电子的存储位点, 并利用芴基 9-位共轭打断 实现对存储电荷的阻挡, 表现出双极性电荷存储达到