Organic Transistor Nonvolatile Memory with Three-Level Information Storage and Optical Detection Functions

By the current processing technology, it is a challenge to obtain ultrahigh-density information storage in the conventional binary floating-gate-based organic field-effect transistor (FG-OFET) nonvolatile memories (NVMs). To develop a multilevel memory in one cell is a feasible solution. In this work, we demonstrate FG-OFET NVMs with an integrated polymer floating-gate/tunneling (I-FG/T) layer consisting of poly(9,9-dioctylfluorene-co-benzothiadiazole) (F8BT) and polystyrene. The photoelectric effect of organic/polymer semiconductors is used to improve the controllability of the polarity and the number of the charges stored in the floating-gate. The FG-OFET NVMs integrate light sensitivity and nonvolatile information storage functions. By selecting suitable optical and electrical programming/erasing conditions, three-level information storage states, corresponding to electron storage, approximate neutrality, and hole storage in the floating-gate, are achieved and freely switched to each other. The memory mechanism and the dependence of the memory performances on the F8BT contents in I-FG/T layers are investigated. As a result, good memory performances, with mobility larger than 1.0 cm² V^-1 s^-1, reliable three-level switching endurance over 100 cycles, and stable three-level retention capability over 20 000 s, are achieved in our memory. Furthermore, an imaging system with a nonvolatile information storage function is demonstrated in a 16 × 5 array of FG-OFET NVMs.