Multifunctional Organic Phototransistor-based Nonvolatile Memory Achieved by UV/Ozone Treatment of the Ta₂O₅ Gate Dielectric

Abstract

An organic phototransistor (OPT) shows nonvolatile memory effect due to its novel optical writing and electrical erasing processes. In this work, we utilize an organic light-emitting diode (OLED) as the light source to investigate OPT-based memory (OPTM) performance. It is found that the OPTM can be used as either flash memory or write-once read-many-times memory by adjusting the properties of the Ta2O5 gate dielectric layer. UV/ozone treatment is applied to effectively change dielectric properties of the Ta2O5 film. The mechanisms for this are examined by X-ray photoelectron spectroscopy and capacitance-voltage measurement. It turns out that the densities of oxygen vacancies and defects in the first 1.8 nm Ta2O5 films near the Ta2O5/semiconductor interface are reduced. Furthermore, for the first time, we use this multifunctional OPTM, which unites the photosensitive and memory properties in one single device, as an optical feedback system to tune the brightness of the OLED. Our study suggests that these OPTMs have potential applications in tuning the brightness uniformity, improving the display quality and prolonging the lifetime of flat panel displays.

Geometrical Structure and Interface Dependence of Bias Stress Induced Threshold Voltage Shift in C60-Based OFETs

“…The performance of OFETs has been improved, and now they are comparable to the amorphous silicon transistors. 1−3 The applications are foreseen as a driver of flat panel display, 4 memory devices, 5 smart labels, 6 and biological sensor. 7,8 The stability of OFETs is a critical requirement for practical applications, but the OFETs are giving unstable characteristics under continuous bias stress.…”

Flexible and Transparent Organic Phototransistors on Biodegradable Cellulose Nanofibrillated Fiber Substrates

“…We believe that the response time can be further improved by optimizing the device design, including the semiconductor material, aligned gate electrodes, and channel lengths. In recent years, there have been many attempts to research pentacene‐based OPT devices with Au electrodes for detecting visible light, showing less than 3 A W −1 of the photoresponsivity and switching characteristics in response to turning the light on/off . Our pentacene‐based devices with transparent electrodes exhibit a larger photoresponsivity (up to 54.8 A W −1 ), which is similar to that of single crystalline semiconductor based flexible phototransistor and faster response time than other reported organic phototransistors.…”

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

“…Apart from the development of high‐mobility and photoactive organic semiconductors as well as new device architectures, functional high‐performance OPTs can be built by dielectric/semiconductor interface engineering. Since the charge carriers are generated and transported directly at the dielectric/semiconductor interface under an applied electric field, the surface roughness, polarity and charge distribution of this interface can dramatically affect the performance of OPTs . In addition, intrinsic characteristics of dielectric materials, for instance, permittivity, also have significant influence on the carrier transport in semiconducting layer .…”