Scientists for the first time unveiled new graphene light-emitting devices with spectrally variable changes

Recently, the research team of Tian Ling, a professor at the Microelectronics Institute of Tsinghua University, published a linearly-labeled flexible all-graphene-based field-controlled light-emitting device ("A spectrally tunable all-graphene" on Nature Communications. A research paper based on -based flexible field-effect light-emitting device", for the first time, discloses a light-emitting device that can regulate the wavelength of light emitted by voltage. Unlike traditional fixed-wavelength LEDs, the new device's illuminating wavelength (in a single device) can be continuously adjusted from 750nm to 450nm, breaking through the color synthesis of existing display devices, and is expected to be suitable for contemporary displays, illumination, and Communication technology has revolutionized its influence. Wang Xiaomu, a postdoctoral fellow at Yale University, and Tian He, a Ph.D. student in the Department of Micro-Nano Electronics, Tsinghua University, are the co-first authors of the article. Professor Ren Tianling from the Department of Micro-Nano Electronics of Tsinghua University is the author of the paper.

The spectrum of the emission wavelength is regulated by the gate voltage.

To date, in all LED devices, the illuminating color/wavelength is determined by the luminescent material. For existing LEDs, once the device is prepared, its wavelength of illumination is fixed. Conventional display or illumination technology achieves the representation of color or the synthesis of white light by adjusting the brightness of several fixed colors (typically using three primary colors of red, green, and blue). The wavelength/color-adjustable LEDs reported for the first time in this article, while achieving excellent color fidelity, can also significantly reduce the number of light-emitting units in the display device, thereby greatly optimizing the drive circuit and reducing power consumption. The results of the project have far-reaching significance in related fields. The reviewer of the paper commented, “This work is expected to open up new research directions in the field of light-emitting devices”, “this work is exciting and influential”.

A mechanism diagram that regulates the wavelength of the light emitted by the gate voltage.

Graphene materials, which have unique physical properties, are widely used in topics such as controllable photons/optoelectronic devices. However, due to its high band gap and high non-luminous recombination characteristics, graphene-based light-emitting devices are a difficult problem in the academic world and a long-term blank field. Prof. Ren Tianling's innovative group obtained the semi-reduced srGO material at the interface between graphene oxide and graphene by laser direct writing technology. This material combines the high conductivity of graphene with the wide band gap characteristics of graphene oxide. By constructing an in-plane gate structure, applying a voltage to the gate modulates the Fermi level of the srGO, thereby real-time regulating the center wavelength of the graphene LED illumination. The LED also features high brightness and a flexible device, making it an ideal component for modern LED display, lighting and communication technologies.

In recent years, Professor Ren Tianling has devoted himself to the research of two-dimensional electronic devices such as graphene, especially focusing on new devices that break through the limitations of traditional devices, laying the foundation for a new generation of micro-nanoelectronic device technology, in new graphene-based memories, acoustic devices and sensor devices. Other aspects have been achieved, such as flexible transparent graphene headphones and low-power graphene resistive memory. The research results were supported by the National Natural Science Fund's key projects.

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