Photoinduced Recovery of Organic Transistor Memories with Photoactive Floating-Gate Interlayers

Abstract

Optical memories based on photoresponsive organic field-effect transistors (OFETs) are of great interest due to their unique applications, such as multibit storage memories and flexible imaging circuits. Most studies of OFET-type memories have focused on the photoresponsive active channels, but more useful functions can be additionally given to the devices by using floating gates that can absorb light. In this case, effects of photoirradiation on photoactive floating-gate layers need to be fully understood. Herein, we studied the photoinduced erasing effects of floating-gate interlayers on the electrical responses of OFET-type memories and considered the possible mechanisms. Polymer/C composites were inserted between pentacene and SiO to form photoresponsive floating-gate interlayers in transistor memory. When exposed to light, C generated excitons, and these photoexcited carriers contributed to the elimination of trapped charge carriers, which resulted in the recovery of OFET performance. Such memory devices exhibited bistable current states controlled with voltage-driven programming and light-driven erasure. Furthermore, these devices maintained their charge-storing properties over 10 000 s. This proof-of-concept study is expected to open up new avenues in information technology for the development of organic memories that exhibit photoinduced recovery over a wide range of wavelengths of light when combined with appropriate photoactive floating-gate materials.

Solution‐Processed Wide‐Bandgap Organic Semiconductor Nanostructures Arrays for Nonvolatile Organic Field‐Effect Transistor Memory

“…Previous studies demonstrated that light illumination could generate excitons in the semiconductor layer of OFET memory devices, which can assist the programming/erasing operation with or without external voltage bias. [9,49,50] Therefore, in the erasing process we utilized a white light with light intensity of about 5 mW cm −2 to illuminate the memory device. It was found that the transfer curve shifted back to its initial position (defined as the erased state) after the WG 3 NSs device was illuminated for 1 s. Memory window (ΔV TH ) is an important parameter for memory devices, which is defined as the difference between V TH in the programmed and the erased states.…”

“…In the light-erasing process, when the memory devices are illuminated, a large amount of excitons are generated in pentacene and then move to the pentacene/ WG 3 interface where charge-exciton annihilation subsequently occurs, resulting in the neutralization of trapped holes in WG 3 (Figure S13b,d, Supporting Information). [49,50] Thus, the transfer curve shifts back to the positive-voltage direction. Interestingly, the energy levels of the WG 3 NSs and the WG 3 film appear to be identical, which indicates the same tunneling barrier with pentacene; however, the memory performance of the WG 3 NSs device is far superior to that of the WG 3 film device.…”

“…This is ascribed to a lack of mobile electrons in pentacene in the ambient condition. Previous studies demonstrated that light illumination could generate excitons in the semiconductor layer of OFET memory devices, which can assist the programming/erasing operation with or without external voltage bias . Therefore, in the erasing process we utilized a white light with light intensity of about 5 mW cm −2 to illuminate the memory device.…”

“…Consequently, the transfer curve shifts to the negative‐voltage direction, which is the electric‐programming process. In the light‐erasing process, when the memory devices are illuminated, a large amount of excitons are generated in pentacene and then move to the pentacene/WG 3 interface where charge‐exciton annihilation subsequently occurs, resulting in the neutralization of trapped holes in WG 3 (Figure S13b,d, Supporting Information) . Thus, the transfer curve shifts back to the positive‐voltage direction.…”

Ultrafast Responsive Non‐Volatile Flash Photomemory via Spatially Addressable Perovskite/Block Copolymer Composite Film

“…Yet, to date, there have been limited systematic studies of photomemory that address the photo‐programming time for effective programming process. [ 9–11 ]…”