Crumpling approach enhances photodetectors' light responsivity

April 7, 2016
Stretchable photodetector with enhanced, strain-tunable photoresponsivity was created by engineering the 2-D graphene material into 3-D structures, increasing the graphene's areal density. Credit: SungWoo Nam, University of Illinois

Researchers from the University of Illinois at Urbana-Champaign have demonstrated a new approach to modifying the light absorption and stretchability of atomically thin two-dimensional (2D) materials by surface topographic engineering using only mechanical strain. The highly flexible system has future potential for wearable technology and integrated biomedical optical sensing technology when combined with flexible light-emitting diodes.

"Increasing graphene's low in visible range is an important prerequisite for its broad potential applications in photonics and sensing," explained SungWoo Nam, an assistant professor of mechanical science and engineering at Illinois. "This is the very first stretchable photodetector based exclusively on graphene with strain-tunable photoresponsivity and wavelength selectivity."

Graphene—an atomically thin layer of hexagonally bonded carbon atoms—has been extensively investigated in advanced photodetectors for its broadband absorption, high carrier mobility, and mechanical flexibility. Due to graphene's low optical absorptivity, graphene photodetector research so far has focused on to increase photoabsorption. However, such hybrid systems require a complicated integration process, and lead to reduced due to the heterogeneous interfaces.

According to Nam, the key element enabling increased absorption and stretchability requires engineering the two-dimensional material into three-dimensional (3D) "crumpled structures," increasing the graphene's . The continuously undulating 3D surface induces an areal density increase to yield higher optical absorption per unit area, thereby improving photoresponsivity. Crumple density, height, and pitch are modulated by applied strain and the crumpling is fully reversible during cyclical stretching and release, introducing a new capability of strain-tunable photoabsorption enhancement and allowing for a highly responsive photodetector based on a single graphene layer.

The video will load shortly.
Demonstration of a stretchable crumpled graphene photodetector. The movie demonstrates stretchability under cyclic uniaxial tensile strains reaching a maximum strain of 200 percent, together with dynamic photoresponse of the device to cyclic on-and-off illumination of 405 nm-wavelength light at 0 percent (blue curve) and 200 percent (red curve) strains. Credit: SungWoo Nam, University of Illinois

"We achieved more than an order-of-magnitude enhancement of the optical extinction via the buckled 3D structure, which led to an approximately 400% enhancement in photoresponsivity," stated Pilgyu Kang, and first author of the paper, "Crumpled Graphene Photodetector with Enhanced, Strain-tunable and Wavelength-selective Photoresponsivity," appearing in the journal, Advanced Materials. "The new strain-tunable photoresponsivity resulted in a 100% modulation in photoresponsivity with a 200% applied strain. By integrating colloidal photonic crystal—a strain-tunable optomechanical filter—with the stretchable graphene photodetector, we also demonstrated a unique strain-tunable wavelength selectivity."

"This work demonstrates a robust approach for stretchable and flexible graphene photodetector devices," Nam added. "We are the first to report a stretchable photodetector with stretching capability to 200% of its original length and no limit on detection wavelength. Furthermore, our approach to enhancing photoabsorption by crumpled structures can be applied not only to graphene, but also to other emerging 2D materials."

Explore further: Novel 'crumpling' of hybrid nanostructures increases SERS sensitivity

More information: Crumpled Graphene Photodetector with Enhanced, Strain-Tunable, and Wavelength-Selective Photoresponsivity, DOI: 10.1002/adma.201600482 ,

Related Stories

Novel crumpling method takes flat graphene from 2D to 3D

February 17, 2015

Researchers at the University of Illinois at Urbana-Champaign have developed a unique single-step process to achieve three-dimensional (3D) texturing of graphene and graphite. Using a commercially available thermally activated ...

Wrinkles and crumples make graphene better

March 21, 2016

Crumple a piece of paper and it's probably destined for the trash can, but new research shows that repeatedly crumpling sheets of the nanomaterial graphene can actually enhance some of its properties. In some cases, the more ...

Addressing the weak optical absorption of graphene

September 10, 2014

Graphene-based photodetectors have attracted strong interest because of their exceptional physical properties, which include an ultra-fast response across a broad spectrum, a strong electron–electron interaction and photocarrier ...

Recommended for you

Stiff fibres spun from slime

October 17, 2017

Nature is an excellent teacher – even for material scientists. Researchers, including scientists at the Max Planck Institute of Colloids and Interfaces, have now observed a remarkable mechanism by which polymer materials ...

A new way to harness wasted methane

October 17, 2017

Methane gas, a vast natural resource, is often disposed of through burning, but new research by scientists at MIT could make it easier to capture this gas for use as fuel or a chemical feedstock.

Key to expanding genetic code described

October 17, 2017

Yale scientists have described the atomic structure of a protein that is the key tool in efforts by synthetic biologists to expand the genetic code.


Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.