Hole Transport Bilayer Structure for Quasi‐2D Perovskite Based Blue Light‐Emitting Diodes with High Brightness and Good Spectral Stability

Substantial achievements have been made in green and red perovskite light emitting diodes (PeLEDs) recently. However, blue PeLEDs still lag behind with much lower performances. One of the main reasons is the mass undesirable nonradiative recombination at interfaces and within the perovskite films. In this work, an efficient hole transport bi‐layer structure composed of PSSNa and NiOx is demonstrated to simultaneously inhibit the nonradiative decays between NiOx and perovskite films by reducing NiOx surface defects and improving quasi‐2D perovskite thin film quality by minimizing its pin‐holes and reducing the film roughness. The results show that the dipole feature of PSSNa improves the hole transportation and thus PeLED performances. Moreover, by introducing KBr into the perovskite, its film quality improves and trap states reduce. Eventually, the blue PeLEDs is achieved with a very low turn‐on voltage of 3.31 V accompanied with an external quantum efficiency of 1.45% and a remarkable luminance of 4359 cd m‐2. With further optimization of the perovskite precursor concentration, the highest luminance reaches 5737 cd m‐2, which represents the brightest blue PeLEDs reported to date as far as it is known. Furthermore, the devices also show better spectral stability and operation lifetime as compared to other blue PeLEDs. A hole transport bilayer structure of a NiOx‐PSSNa film and KBr decorated perovskites is introduced in blue perovskite light‐emitting diodes (PeLEDs), which significantly inhibit the nonradiative recombination at interfaces and within the perovskite films. The fabricated devices show a brightest blue PeLED with an impressive luminance of 5737 cd m−2, signaling a great potential toward the practical applications.