Uniform and Large-Area Cesium-Based Quasi-2D Perovskite Light-Emitting Diodes Using Hot-Casting Method

Metal halide perovskites have deep valence band maximums (VBMs). For example, the VBM of CsPbBr3 is 5.8-6.3 eV. Conjugated polymers can be a potential candidate for the hole transport layer because of their deep highest occupied molecular orbital levels, but their poor compatibility with a hydrophilic perovskite precursor results in the formation of a noncontinuous perovskite film. In addition, antisolvent dripping methods for fabricating perovskite films cause spatially inhomogeneous nucleation, which is undesirable for large-scale applications. In this work, efficient and large-area perovskite light-emitting diodes (PeLEDs) are developed by introducing a poly(9-vinylcarbazole) (PVK) interlayer and employing a hot-casting method (substrate preheating). The PVK interlayer increases the depth of the VBM of NiOx (from 5.1 to 5.5 eV), resulting in efficient hole injection. The thermal energy of the preheated substrate facilitates not only the growth of a continuous and pinhole-free perovskite film, but also the formation of a highly crystalline and preferentially oriented perovskite structure, resulting in improved luminescence properties. Therefore, PeLEDs fabricated using an optimal preheating temperature show an improved external quantum efficiency (from 3.08% to 8.44%) with spatially uniform electroluminescence. Finally, the development of uniform and large-area PeLEDs (with an active area of 12.8 cm(2)) is demonstrated.