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Organic nonvolatile memory based on OFET is an essential element in organic electronics, which integrates nondestructive data processing and reliable data storage [1,2]. It is reported the memory window is sensitive to light illumination. However, the fundamental of the light-assisted program, especially the photon energy dependence of memory performance, needs to be clarified with a clear physical picture. In our work, the charge trapping process in the organic nano-floating-gate memory was comparatively studied by light response measurements, where light sources with different wavelengths of 408 nm, 532 nm, and 652 nm were employed. The positive threshold voltage shift was observed for all lights and increased up raising the light intensity, while the negative threshold voltage shift was only observed under 408 nm light illumination. It is proposed that the light with photon energy higher than the HOMO–LUMO gap of pentacene can induce the minority multiplication effect, which leads to significant positive threshold voltage shift but no obvious impact on negative threshold voltage shift. Whereas the light with photon energy in excess of the injection barriers at the pentacene/PS interface can additionally cause the excitation-induced injection effect, corresponding to hole injection into floating gate from the HOMO of pentacene, which realizes further negative threshold voltage shift [3]. The photon-energy-dependent light effects could be utilized to reduce the operation voltage of organic nano-floating-gate nonvolatile memories, and motivate the development of organic energy-resolved photosensors.
References:
[1] Y. L. Guo, G. Yu, Y. Q. Liu, Advanced Materials, 2010, 22, 4427-4447.
[2] X. J. She, C. H. Liu, Q. J. Sun, X. Gao, S. D. Wang, Organic Electronics, 2012, 13, 1908-1915.
[3] X. Gao, C. H. Liu, X. J. She, Q. L. Li, J. Liu, and S. D. Wang, Organic Electronics, 2014, 15, 2486-2491.
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