Unraveling The Role Of Crystallization Dynamics On Luminescence Characteristics Of Perovskite Light-Emitting Diodes

Metal halide perovskites are one of the most promising materials for optoelectronic applications owing to their unique optoelectronic properties. In the pursuit of achieving the efficient perovskite light-emitting diodes (PeLEDs), the critical role of crystallization dynamics on luminescence properties of cesium lead bromide (CsPbBr3) perovskite films has been clarified based on the characterizations of in situ photoelectron spectroscopy, synchrotron-based grazing incidence X-ray diffraction, and device fabrication. The crystallinity and crystal orientation of CsPbBr3 perovskite films has been effectively controlled when tuning the underlayer of poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) with the ethanolamine modification. The fast crystallization with the formation of pure cubic phase (alpha-CsPbBr3) reveals a substantial boost in luminance and device efficiency of PeLEDs, whereas the performance degradation occurs due to the phase transition from alpha-CsPbBr3 to orthogonal phase (gamma-CsPbBr3) along with the appearance of PbBr2. The decomposition of organic additives in the perovskite films is a key factor that results in this phase transition, which changes the absorption and band gap as confirmed by the density functional theory calculation. These experimental and theoretical findings provide a better understanding of the crystallization dynamics of perovskite emitters and their influence on device performance by tuning the substrate properties.