Transparent and conformable organic light-emitting diodes for skin-attachable invisible displays

A skin-attachable invisible display offers a new opportunity in next-generation electronic application, such as smart contact lenses, human-machine health monitoring interfaces and soft electronic skins. In response to this trend, transparent organic light-emitting diodes (OLEDs) offer enormous advantages in future skin-attachable invisible displays, including excellent flexibility and superior efficiency. Although several approaches reported recently attempt to manufacture transparent and flexible OLEDs, it is still a tremendous challenge to simultaneously meet the desired optical and mechanical properties. Herein, we develop a feasible strategy to achieve transparent and conformable OLEDs (TC-OLEDs). Benefiting from the intrinsic high transparency and outstanding deformability of our electrodes, the whole device shows high transmittance up to 85.0% at a wavelength of 400 nm and high mechanical flexibility with skin-like conformability. More strikingly, the resulting device maintains excellent photoelectric performance with a maximum current efficiency (CE) of 56.8 cd/A and external quantum efficiency (EQE) of 17.1%. Based on the versatile TC-OLEDs, we also report an all-organic and all-conformable invisible display driven by transparent and conformable organic thin film transistors (TC-OTFTs) for the first time. This work offers a meaningful guidance for the construction of TC-OLEDs and the development of skin-attachable invisible displays.