The optical and electrical properties of inorganic perovskite nanocrystals make them useful for light-emitting diodes (LEDs) and flexible display applications. William W. Yu, Jilin University, Changchun, China, and Louisiana State University, Shreveport, USA, Yu Zhang, Jilin University, and colleagues have fabricated highly flexible perovskite LEDs using CsPbI₃ perovskite nanocrystals as emitters, a photopolymer as a flexible substrate, and an Ag film as the cathode.

The CsPbI₃ nanocrystals were prepared from Cs₂CO₃ and PbI₂ via a Cs‐oleate precursor. The Ag film was grown on a silicon wafer, leading to an ultra-smooth surface. This enhances electron injection and reduces short circuits between the anode and the cathode. The photopolymer (Norland Optical Adhesive 63) was spin‐coated onto the Ag film and cured under UV light. The perovskite nanocrystals were also spin‐coated onto the device.

The resulting flexible red LEDs have a low turn-on voltage of 2.0 V and an external quantum efficiency of 8.2 %. The LEDs’ brightness remained at 70 % of the initial value after bending them 1,000 times. This demonstrates their flexibility and mechanical robustness. These results could lead toward flexible perovskite nanocrystal displays.

• Highly Flexible CsPbI₃ Perovskite Nanocrystal Light-Emitting Diodes,
  Min Lu, Hua Wu, Xiaoyu Zhang, Hua Wang, Yue Hu, Vicki L. Colvin, Yu Zhang, William W. Yu,
  ChemNanoMat 2018.
  https://doi.org/10.1002/cnma.201800359