Lund University develops branched nanowire led to reduce light trapping losses

The new design addresses this limitation through the geometry of the nanostructures themselves. Light is emitted from very thin side branches that extend outward from a central nanowire. When these branches are made thinner than the wavelength of light, the physical conditions that cause total internal reflection no longer apply in the same way. Magnus Borgström, professor of solid-state physics at Lund University, stated that this geometry could theoretically enable a very high light output, noting that in principle it would be possible to release virtually all the light generated within the structure.

In the device architecture, the central nanowire core serves to inject charge carriers, while light emission takes place exclusively in the thin side branches. A critical aspect of the research was demonstrating that light is generated in the branches and not through re-absorption of light originating from the core. The researchers designed the core so that it does not itself emit light, and their results confirmed that emission occurs precisely in the intended locations. Yue Zhao, a doctoral student in solid-state physics and co-author of the study, described this confirmation as an important outcome, stating that knowing where light is generated is crucial for the technology to function as intended.

The technology remains at the research stage and has not yet reached the efficiency levels of commercial LEDs. A key challenge identified by the research team is reducing losses associated with surface defects in the nanostructures. However, the researchers note that the nanoscale nature of the structures means less material is required, which may contribute to lower manufacturing costs over time. If the technology proves successful, it could also eliminate the need for the costly surface processing methods currently used to improve light extraction in conventional LEDs. Borgström described the demonstration that the technology works at all as an important first step, with the current focus on optimizing materials and structures to achieve greater efficiency. The research team is continuing work toward that goal, with potential long-term applications ranging from public lighting to advanced optoelectronic systems.