GaN microrods on graphene substrates enable bendable optoelectronics devices
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GaN microrods on graphene substrates enable bendable optoelectronics devices
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endy” light-emitting diode (LED) displays and solar cells crafted with inorganic compound semiconductor microrods are moving one step closer to reality, thanks to graphene and the work of a team of researchers at Seoul National University (SNU). While most flexible electronics and optoelectronics devices are fabricated using organic materials, inorganic compound semiconductors such as GaN can provide further advantages, including superior optical, electrical, and mechanical properties. One major obstacle to their use, however, is the difficulty of growing them on flexible substrates. In the September issue of APL Materials (DOI: 10.1063/1.4894780), Gyu-Chul Yi and colleagues describe their work growing GaN microrods on graphene to create transferable LEDs and enable the fabrication of bendable and stretchable devices. “GaN microstructures and nanostructures are garnering attention within the research community as light-emitting devices because of their variable-color light emission and high-density integration properties,” says Yi. “When combined with graphene substrates, these microstructures also show excellent tolerance
Hybrid device functions as self-recovering electrochromic window and self-charging battery
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mart windows are finding many uses in architectural and vehicle applications. Their ability to reversibly switch from transparent to opaque provides important functionality, like reducing solar heat gain and glare, without sacrificing the benefits of broad views and natural lighting. However, one practical challenge for using them in buildings is the need for an external bias voltage, which means that electricians must run extra
for mechanical deformation.” Ultrathin graphene films consist of weakly bonded layers of hexagonally arranged carbon atoms held together by strong covalent bonds. This makes graphene an ideal substrate “because it provides the desired flexibility with excellent mechaniRendering of the microrod growth process. Credit: Seoul National University. cal strength—and it’s also chemically and physically stable at temperatures in excess onto underlying substrates,” Yi says. of 1000°C,” says Yi. When the team put the microrod For the GaN microrod growth, LEDs to the test, they found that “the the very stable and inactive surface resulting flexible LEDs showed intense of graphene offers a small number of electroluminescence (EL) and were relinucleation sites for GaN growth, which able—there was no significant degradawould enhance three-dimensional island tion in optical performance after 1000 growth of GaN microrods on graphene. bending cycles,” says Kunook Chung, The team uses a catalyst-free metal– the article’s lead author and graduate organic chemical vapor deposition student at SNU. (MOCVD) process. “By taking advantage of larger-sized “Among the technique’s key criteria, graphene films, hybrid heterostructures it’s necessary to maintain high crystalcan be used to fabricate various eleclinity, control
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