Memory Devices Decreasing the Energy Consumption of Memory Devices by Enhancing the Conjugation Extent of the Terminal Electron- Donating Moieties within Molecules Rongcheng Bo, [a] Hongzhang Liu, [a] Qianhao Zhou, [a] Dongyun Chen, [a] Qingfeng Xu, [a] Najun Li, [a] Hua Li, [a] and Jianmei Lu* [a, b] Abstract: Three small organic molecules that contained a phenothiazine backbone and triphenylamine (TPA), carba- zole (CZ), or anthracene (AN) as a terminal electron donor were synthesized and fabricated in ITO/organic film/Al sand- wiched memory devices. The influence of the extent of con- jugation in the three molecules on the performance of their corresponding devices was investigated and the results showed that all of the fabricated devices exhibited nonvola- tile ternary WORM character, whilst the switch threshold vol- tages decreased on moving from TPA to CZ and AN, which is promising for low-power-consumption data storage. These results revealed that tailoring the extent of conjuga- tion in the terminal electron donor in the D–A molecules could effectively optimize the device performance, in partic- ular the switch-threshold voltage, which could be instructive for the design of low-energy-consumption memory materi- als. Introduction The era of information explosion has begun; [1–5] therefore, the storage of large masses of data efficiently, steadily, and safely has become a great technical challenge facing scientists. Over the past few years, tremendous efforts have been made in finding the next generation of electrical memory materials that can be employed into memory devices with low switch-thresh- old voltages (V th ), high ON/OFF current ratios, and high stabili- ties. [6–14] In recent years, electrical memory devices based on small organic molecules have been of considerable interest, owing to their well-confined structures, good stimuli-response, ease of purification, and versatility in molecular design. [15–18] In 2010, we reported a small-molecule-based ternary-data-storage device based on the charge-trap theory, which may be used to realize the next generation of high-density data storage (HDDS) devices. [19] However, optimization of the performance of such devices through tuning their molecular structure and clarifying the relationship between molecular structure and device performance still need to be explored in depth. In our previous work, we found that the device performance, such as V th value, ON/OFF current ratio, and stability, could be marked- ly affected by the molecular length, [20] alkyl-chain length, [21, 22] and the number and electron-withdrawing strength of the ac- ceptor moieties. [23, 24] From these reports, achieving lower V th values for decreased energy consumption remains a notable research target. According to charge-trap theory, multi-level currents devices could be realized as the different depth “traps” within the molecular backbone are successively filled under an electric field. Herein, by employing PTZO-CN as an electron acceptor and TPA, CZ, and AN as electron donors, we supposed that the V th value of the fabricated memory devices could be tuned, owing to differing levels of conjugation between the donor and the acceptor. Our results showed that the V th values of the fabricat- ed devices successively decreased on changing the electron donor from TPA to CZ and AN, owing to the better conjuga- tion and improved planarity of CZ and AN groups within the molecular backbones compared to TPA. Furthermore, AN- PTZO-CN had a smaller dihedral angle between the electron donor (AN) and the neighboring benzene ring than CZ-PTZO- CN, thereby enabling better conjugation and coupling of the frontier orbitals between the donor and acceptor, which led to enhanced electron-delocalization ability and resulted in the “traps” being filled relative easily and having the lowest switch-threshold voltages among the three devices. We hope [a] Dr. R. Bo, H. Liu, Q. Zhou, Dr. D. Chen, Prof. Q. Xu, Dr. N. Li, Dr. H. Li, Prof. J. Lu College of Chemistry Chemical Engineering and Materials Science Collaborative Innovation Center of Suzhou Nano Science and Technology Soochow University Suzhou, 215123 (P. R. China) E-mail : lujm@suda.edu.cn [b] Prof. J. Lu State Key Laboratory of Treatments and Recycling for Organic Effluents by Adsorption in Petroleum and Chemical Industry Soochow University Suzhou, 215123 (P. R. China) Supporting information for this article is available on the WWW under http://dx.doi.org/10.1002/asia.201403119. Chem. Asian J. 2014, 00,0–0  2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim 1 && These are not the final page numbers! ÞÞ Full Paper DOI: 10.1002/asia.201403119