Flexible Graphene-Based Infrared Imaging via Lithium-Intercalation-Enabled Absorption Modulation

Graphene exhibits broad-spectrum absorption and dynamic modulation capabilities, standing at the forefront of light-matter interaction research. Thicker graphene was needed to enhance the interaction with infrared optical signals. Some commonly used methods are irreversible or only suitable for a single or few-layer graphene. Exploring novel modulation methods for thicker graphene to acquire efficient absorption and image display in infrared bands has gradually become an important research focus. In this study, lithium intercalation technology was adopted to modulate the infrared radiation efficiency of the graphene film. With the bias voltage of 3.55V~3.85V, the infrared absorbance (ABS) changed from 0.329 to 0.116 at <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$25~\mu $ </tex-math></inline-formula> m. During this modulation, both infrared and visible images were displayed on the surface of the multilayer graphene. The arbitrary infrared image could be obtained on the all-flexible display panel by patterning the NCM (LiNi<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$_{\mathbf {x}}$ </tex-math></inline-formula>Co<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$_{\mathbf {y}}$ </tex-math></inline-formula>Mn<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$_{\mathbf {1-x-y}}$ </tex-math></inline-formula>O<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$_{\mathbf {2}}$ </tex-math></inline-formula>) substrate. In this work, the Arabic numerals “<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0\sim 9$ </tex-math></inline-formula>” and the Morse code (N, U, C) were dynamically displayed in sub-seconds. All these high-resolution (1 mm feature size), rapid image switching, and all-flexible characteristics provided the theory and technical support for further graphene-based infrared display devices. The modulation technique offers a novel way for multispectral optical display and encrypted information in graphene-based flexible devices.