Nu�o Amador
Flexible nanowire-based light emitter
Université Paris-Sud
Flexible light emittingdiodes (LEDs) are today a topic of intense research driven by applications such asbendable displays, conformable light sources, bio-medical devices, etc. Today theflexible technology is dominated by organic semiconductors, which however exhibitlow efficiency and a limited lifetime. The conventional inorganic semiconductor devices are mechanically rigid; the fabrication of flexible devices from thin film structures is quite challenging and requires microstructuring of the active layer. It is advantageousto shrink the active element dimensions and to use bottom-up nanostructures, suchas nanowires, instead of two-dimensional films. Nanowires show remarkablemechanical and optoelectronic properties stemming from their anisotropic geometry,high surface-to-volume ratio and crystalline perfection. Moreover they are mechanicallyflexible and can stand high deformations without plastic relaxation.
The objective of this PhD project is to propose a novel solution for flexible optoelectronic devices using polymer-embedded nanowires. These devices will combine the high efficiency and the long lifetime ofinorganic semiconductor materials with the high flexibility of polymers. In particular, the objectiveis to develop a reliable technology for red, green and blue nanowire flexible micro-LEDs and to demonstrate a prototype of a bendable display. Nanowire arrays embedded in a flexible film and lifted-off from their native substrate will beused as the active material. Figure 1 shows an example of flexible blue, green andphosphor-converted white LEDs previously demonstrated in the group.
Fig.1 Flexible nanowire blue, green and white LEDs under operation.
The lift-off and transfer procedure enables the assembly of free-standing layers ofnanowire materials with different bandgaps without any constraint related to latticematchingor growth conditions compatibility. This concept therefore allows for alarge design freedom and modularity since it enables combination of materials withvery different physical and chemical properties, which cannot be achieved bymonolithic growth. In this PhD project, we will make use of nanowires of different semiconductor materials for RGB LEDs(InGaN for the blue and green colors with different In content and GaAsP for the red color).
