Here, the original graphene substrate serves as the top conductive electrode in what becomes a vertical “flip chip” GaN/AlGaN LED configuration. The GaN nucleation droplets coalesce at the top of the nanowires which are then capped with a gold electrode, while a metal contact on the continuous graphene electrode allows for efficient vertical current injection through the nanocolumns, the paper reports. Based on the measured temperature-dependent photoluminescence of their device, the authors estimate its internal quantum efficiency (IQE) to around 46%.
This technology is patented by NTNU and licensed by CrayoNano AS who claims on its website a 10-fold wall plug efficiency (WPE) increase over other state-of-the-art UV LEDs. Weman and his co-workers aim to further increase the devices’ IQE by optimizing the nanowire's geometry through various growth parameters. With this new development, the company aims to bring significant efficiency improvements and cost reductions to UV lighting applications such as water and food processing disinfection, air purification and environmental monitoring and life science measurements.
Questioned about its business model, Weman said it was still an open question whether CrayoNano would become a UV LED chip producer or if the company would license the technology to established UV LED manufacturers. The efficiency is still behind today’s traditional UV LEDs, the CTO admitted, adding that CrayoNano is an early stage company and expects to have commercial devices ready in three to four years. CrayoNano is backed by Norwegian investors with the largest one being “Norsk Innovasjonskapital” fund NIK III.
Norwegian University of Science and Technology - http://www.ntnu.no
CrayoNano AS - www.crayonano.com