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

By the current processing technology, it is a challenge to obtain ultra-high density information storage in the conventional binary floating-gate based organic field-effect transistor (FG-OFET) nonvolatile memories (NVMs). To develop a multi-level 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 on the polarity and amount 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 electrons storage, approximate neutrality, and holes storage in the floating-gate, respectively, are achieved and freely switched 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 x 5 array of FG-OFET NVMs.