Perovskite light-emitting diodes (PeLEDs) are a promising technology with tunable bandgaps, high color purity, and good carrier mobility. While red and green PeLEDs with external quantum efficiencies of over 20 % have been developed, building efficient blue PeLEDs is more challenging. Existing blue PeLEDs are usually based on 2D structures or nanoparticles, because bulk perovskites generally show worse performance—caused by insufficient quality of the perovskite films. Creating high-quality bulk perovskite films could allow for improved performance, better electrical properties, and lower costs.
Gi-Hwan Kim, Gyeongsang National University, Jinju, Republic of Korea, Jin Young Kim, Ulsan National Institute of Science and Technology (UNIST), Republic of Korea, and colleagues have developed a fabrication method for blue PeLEDs based on stable bulk inorganic halide perovskites, which were synthesized using an anion-exchange method. The team first prepared bulk CsPbBr3 perovskite films using a spin-coating method. Then, the films were dipped into a mixture of chloroform and tributylphosphine. In this step, an exchange reaction replaces bromine atoms in the perovskite with chlorine atoms, resulting in CsPbBr3-xClx films with a blue emission.
This fabrication method avoids the use of inorganic Cl sources, which can have low solubilities and lead to insufficient film coverage on the substrate. The optical properties of the perovskite films can be tuned by changing the reaction time of the anion exchange. The anion-exchanged perovskites are stable and can be used to create highly saturated PeLEDs. The devices achieved maximum luminances of 1468 cd m–2 and 494 cd m–2 for emission peaks at 490 nm and 470 nm, respectively.
- Highly Stable Bulk Perovskite for Blue LEDs with Anion-Exchange Method,
Yung Jin Yoon, Yun Seop Shin, Hyungsu Jang, Jung Geon Son, Jae Won Kim, Chan Beom Park, Dohun Yuk, Jongdeuk Seo, Gi-Hwan Kim, Jin Young Kim,
Nano Lett. 2021.