Enhanced Flexibility and Stability of Emissive Layer Enable High-Performance Flexible Light-Emitting Diodes by Cross- Linking of Biomass Material

摘要

Flexible perovskite light-emitting diodes (LEDs) have been highly expectedto realize advanced wearable optoelectronic applications due to the excellentoptoelectronic properties of perovskites. However, the poor water andoxygen stability and limited flexibility of perovskites prevent their commercializationand applications in flexible LEDs. Herein, the low-cost and greenbiomass materials-ethyl cellulose (EC) is added in the CsPbI3 nanocrystals(NCs), acting as a cross-linker between neighboring halide octahedrathrough hydrogen bonds and PbO coordination bonds. It reduces thedefect densities of NCs, leading to improved photoluminescence quantumyield. Simultaneously, the synergistic effect of efficient defect passivationand hydrophobic ether groups of EC significantly improve the environmentstability of NCs. Additionally, the favorable flexibility of EC and cross-linkingbetween EC and perovskite NCs improve the deformation resistance of theperovskite layer with stable photoluminescence and negligible cracks afterrepeated bending. Consequently, flexible LEDs based on the EC-passivatedCsPbI_3 NCs achieved a record external quantum efficiency of 12.1 andsignificantly enhanced operational stability. Moreover, the flexible LEDs showsmall luminance degradation after bending for 1000 cycles at a radius of3 mm, and still retain high performance even after repeatedly bending at anultrasmall bending radius of 1 mm.