Highly Efficient and Flexible Perovskite Nanocrystal Light-Emitting Diodes on Disposable Paper Substrates

Perovskite nanocrystals have been widely applied in the field of light-emitting diodes (LEDs) due to their excellent optoelectronic properties. However, there is generally a serious degradation of device efficiency when transferring the device from rigid to flexible substrates due to the high roughness, poor wettability, and low endurance temperature of flexible substrates. Herein, a highly flexible perovskite light-emitting diode (PeLED) by utilizing label paper as substrates and poly(methyl methacrylate) (PMMA) as the modified layer was reported. Compared with the reference device based on commonly used polyethylene terephthalate (PET) substrates, the label paper/PMMA-based devices did not show the degraded device performance when transferring from rigid to flexible substrates. This is mainly because of low roughness and good wettability of PMMA-modified label paper, which significantly improve the film-forming ability of the bottom electrode and functional layer. Furthermore, the flexibility of both devices was explored by a three-point bending flexural test, indicating that the label paper-based device has better bending stability than the polyethylene terephthalate-based one due to the lower flexural modulus for label paper. As a result, the label paper-based flexible PeLEDs exhibited the highest external quantum efficiency (EQE) of 14.3% among perovskite nanocrystal-based flexible LEDs and preeminent flexibility with 29% luminance degradation after bending for 1000 cycles at a small radius of 1.5 mm. This extension of the substrate to paper will widen the opportunity of PeLEDs in extremely flexible and inexpensive applications.