Investigation of light programmable non‐volatile memory in an organic phototransistor

Abstract

Excellent non‐volatile memory characteristics have been demonstrated under the optoelectric conditions for organic phototransistors (OPTs). The high photosensitivity shown as reversible shifts in light‐induced VTH exhibits a large memory window for programming caused by the excited immobile carriers (electron) trapped as a function of the electrical bias and the light intensity. The long life span of stored electrons also reveals promising behavior with respect to data retention as well as the electrical reliability to serve as a data storage medium with the non‐volatile memory characteristic in OPTs. The VTH recovery accelerated by the reversible bias stress for the stored charges under irradiation shows that the erasing behavior is clearly brought by the discharge process of long‐lived electrons occupied in deep states. Plausible mechanisms in the energy band are discussed for the programming and erasing process, which provides a fundamental understanding of the intrinsic charge storage behavior in OPTs. (© 2015 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim)

Efficient organic photomemory with photography-ready programming speed

“…This could be disadvantageous because light enters into the device layers (channels or dielectrics) mostly through the channel area that is not covered by the metallic source/drain electrodes ( Fig. 4b ) 23 24 25 26 27 28 29 . In that case, the light-programming, requiring both electric field and photon-absorption, is discouraged by significantly low electric field in the channel area, or by the lack of photons in the region under source/drain electrodes.…”

“…They have been developed with various structures and operating mechanisms 14 such as photoconductors 15 16 , photodiodes 17 18 19 , phototransistors 20 21 22 , and photomemories. Among them, photomemories combine both photosensors and memories, and thus enable simplified circuitry by eliminating the need for independent memory components to store the output of the photosensors 23 24 25 26 27 28 29 . In particular, photomemories based on a transistor structure provide additional advantages, in that they allow for further simplification of pixel-level structure by serving as photosensors, memories, and switching devices all at once.…”

Recent Progress in Organic Phototransistors: Semiconductor Materials, Device Structures and Optoelectronic Applications

“…Acenes are one of the widely investigated small molecule materials in OPTs. For example, pentacene‐based phototransistors regarding the effect of light intensity, bias stress reliability, wavelength‐dependent sensitivity, gate dielectric and channel lengths have been systematically studied. However, pentacene‐based OPTs showed relatively low light‐sensitivity probably due to the thin absorption thickness.…”

Development of High‐Sensitivity Poly(2,7‐(9,9‐dioctylfluorene)‐alt‐5,5‐(4′,7′‐di‐2‐thienylbenzo [c][1,2,5]thiadiazole)) Thin‐Film‐Based Phototransistors by the Ribbon‐Floating Film Transfer Method

“…Organic field-effect transistors (OFETs) have potential applications in the field of flexible displays, plastic radio-frequency identification (RF-ID) tags, complementary integrated circuits, memory, devices, and sensors. [1][2][3][4][5][6][7][8][9][10][11][12] Utilizing OFETs as light sensors is of interest as the active organic layer can be tailored to absorb photons of specific energy which when combined with the gain offered by the transistor can result in a highly sensitive device. [13][14][15][16][17][18][19] Recently, polymer-based organic photosensitive transistors (OPTs) have been demonstrated, opening the possibility to print these devices on flexible substrates, leading to flexible optoelectronic systems.…”