3D Radial Junctions for Robust and Flexible Optoelectronics

Abstract Marrying nanostructures with thin films is a recent trend in flexible optoelectronics to improve light trapping and mechanical stability. Radial junction (RJ) a‐Si:H thin film optoelectronics, directly deposited upon the vapor‐liquid‐solid (VLS) grown silicon nanowires (SiNWs), can pave the way to achieving excellent flexibility and a high power‐to‐weight ratio (PTWR). Thanks to their vertical‐standing geometry, SiNWs framework can enhance the mechanical stability of RJ units, by keeping the working region far away from the stress‐rich substrate surface. Using low‐melting‐point metals as catalysts, the SiNW array can be fabricated at a low temperature down to 350 °C in a PECVD system, making it possible to directly construct robust RJ units on flexible, low‐cost substrates, such as Al foil. In this review, the recent progress of the flexible RJ a‐Si:H thin film solar cells/photodetectors that are directly fabricated on the surface of low‐cost flexible substrates is reviewed. Moreover, these RJ flexible optoelectronics are demonstrated for use in wearable and real‐time health monitoring, and as cardiac pacemakers for heart stimulation. This RJ technology highlights a promising potential to establish high‐performance, low‐cost, mechanically stable flexible optoelectronic for wearable, portable applications.