Impact of the Bending on the Electroluminescence of Flexible InGaN/GaN Light-Emitting Diodes

The role that the mother substrate plays to influence the performance of InGaN/GaN-based light-emitting diodes (LEDs) onto the adhesive flexible tapes is addressed in this letter. For this purpose, the electroluminescent (EL) spectra and current density–voltage ( $J$ – $V$ ) characteristics of flexi-LEDs are studied under different convex bending configurations (from a curvature radius of infinity to 1.4 cm), showing only one peak around 442 nm in all the cases. Both the EL spectra and $J$ – $V$ characteristics are affected by the applied tensile stress when the flexi-LED is bent. In fact, an increase of the applied tensile strain from 0.02% to 0.09% results in a red-shift of the EL peak energy by 3 meV at 0.7 mA, and a drop of the current at high forward bias. In addition, such flexi-LEDs exhibit a reversible response when a significant mechanical deformation is applied.