Figure 4 (a) Schematic illustration of the OFET device. Transfer curves of the (b) AG1, (c) UG1, and (d) DG1 based OFET devices for the programming and erasing processes.
To gain an insight into the specific characteristic of nanogrids, we designed and fabricated the organic field effect transistor (OFET) memory devices, in which the as prepared AG1, UG1 and DG1 thin films served as charge trapping layers (CTL). The sketch mapping of the devices was shown in Figure 4a and the detailed fabrication procedures were given in section VII in the supporting information. The transfer curves of the devices were shown in Figure S7a-c. All the fabricated devices exhibited typical p-type behavior with the hole carrier mobility of about 0.6 cm2V-1s-1 and ION/IOFF over 104. As shown in Figure S7d-f, the output characteristics of the devices show good current modulation with well-defined linear and saturation regions. The transfer curves before and after different stimulus conditions were further investigated and shown in Figures 4b-d. The memory window (ΔVth) is defined as the difference between the threshold voltage (Vth) of the programmed and erased states. For the programming process, when applying a gate voltage (VGS) of 40 V with 145 mW/cm2 for 1 s, the photogenerated electrons could be trapped by the CTL, resulting in the positive shift (ΔVth-e) of the transfer curves. For the erasing process, with a reverse VGS of ‒30 V under dark for 1 s was applied, the transfer curves shifted to the negative direction (ΔVth-h) owing to the holes transfered from pentacene and trapped by the CTL. The ΔVth of AG1, UG1 and DG1 devices were calculated to be 28.3 V, 12.7 V and 20.5 V, respectively. In comparison, AG1 device show the largest ΔVth with the largest ΔVth-e and ΔVth-h generated in the programming and erasing processes, indicating the excellent electron and hole trapping capacity of AG1 and suggesting the rigid skeleton of nanogrids can be benefit for realizing high performance OFET memory devices.
Conclusions
In summary, we have designed and synthesized a novel series of A-type of axially and centrally chiral nanogrids (AGs) comprising difluorenyl biaromatic derivatives and thiophene derivatives. Our study found that using R /S -BINDFOH (15-20%) as the substrate, as the substrate resulted in a significantly higher yield of AGs compared to mixed BINDFOF (9%). Furthermore, the relevant characteristics of AG1, UG1 and DG1 based OFET memory devices show that nanogrids possess large electron/hole trapping capacity, the AG1 is expected to become the star material for the new generation of semiconductor devices. These findings provides us with a simple and direct synthetic approach to access an array of nanogrids intelligently fused with chiral skeletons, which contribute to the further discovery and application of attractive organic nanogrids.
Experimental