Abstract
Stretchable organic light-emitting diodes are ubiquitous in the rapidly developing wearable display technology. However, low efficiency and poor mechanical stability inhibit their commercial applications owing to the restrictions generated by strain. Here, we demonstrate the exceptional performance of a transparent (molybdenum-trioxide/gold/molybdenum-trioxide) electrode for buckled, twistable, and geometrically stretchable organic light-emitting diodes under 2-dimensional random area strain with invariant color coordinates. The devices are fabricated on a thin optical-adhesive/elastomer with a small mechanical bending strain and water-proofed by optical-adhesive encapsulation in a sandwiched structure. The heat dissipation mechanism of the thin optical-adhesive substrate, thin elastomer-based devices or silicon dioxide nanoparticles reduces triplet-triplet annihilation, providing consistent performance at high exciton density, compared with thick elastomer and a glass substrate. The performance is enhanced by the nanoparticles in the optical-adhesive for light out-coupling and improved heat dissipation. A high current efficiency of ~82.4 cd/A and an external quantum efficiency of ~22.3% are achieved with minimum efficiency roll-off.
Highlights
Stretchable organic light-emitting diodes are ubiquitous in the rapidly developing wearable display technology
The device stability was reinforced by using thin Norland Optical Adhesive 63 (NOA63) for encapsulation, which fabricated a sandwiched structure with thin NOA63, induced a small bending strain, and adjusted the mechanical neutral plane (MNP) at the high Young’s modulus (YM) layers[8,27,28,29]
As the organic light-emitting diodes (OLEDs) devices were encapsulated in a sandwiched structure having a thin NOA63 (9.2 μm) at the top and bottom, the analysis indicates that the small bending strain and the MNP were suitably adjusted to minimize the damage to the efficient layers[8,27,28,29] (Supplementary Fig. 11)
Summary
Stretchable organic light-emitting diodes are ubiquitous in the rapidly developing wearable display technology. Incorporation of OLEDs into wearable[2], epidermal[3], and stretchable electronics[4,5], with color stability, and high brightness under intensely strained bending/stretching has been of major interest This interest has led to various studies on electrodes as a replacement of poly(3,4ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS)[6], and indium tin oxide (ITO)[7,8,9], which included a graphene-based electrode[10], a highly transparent metal-grid[11] and polymer with silver nanowires (AgNWs)[12,13]. This pathway can be provided by the incorporation of metal oxide nanoparticles (NPs) in the thin substrate and can enhance the heat dissipation in optoelectronic devices due to their high, thermal conductivity and porous scaffold design[35]
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