Tailoring the Surface Morphology and Phase Distribution for Efficient Perovskite Electroluminescence.

Metal-halide perovskites are promising light-emitting materials due to their continually tunable emission peak, high color purity, high emission efficiency, and low cost. Incorporating some two-dimensional (2D) perovskites into the three-dimensional (3D) perovskite can facilitate carrier localization to the emitting area and reduce nonradiative recombination. However, the incorporated 2D perovskites typically contain diverse phases with different bandgaps and random distribution, which significantly limits the performance of perovskite light emitting diodes (PeLEDs). Furthermore, the morphology of the quasi-2D perovskite film is also a key issue to the device performance. Herein, through replacing part of FA+ with Cs+, the phase distribution and morphology of perovskite film can be tailored simultaneously. When 20% of FA+ is replaced by Cs+ in the perovskite film, the charge transfer efficiency is enhanced and the current leakage is suppressed. Eventually, the efficiency of PeLED is almost doubled and the stability is also significantly improved.