Octafluoronaphthalene assists in adjusting phase distribution of quasi-two-dimensional perovskite LEDs

Two-dimensional (2D) lead halide perovskites are famous for their high color purity, tunable bandgap, and solution processability as the one of the most promising candidates for light-emitting diodes (LEDs). The 2D perovskite films often make up multiple phases with layered (n) lead halide (from n = 1, 2, 3 to≈∞). However, phase-segregation, especially forming too much small-n phases may lead to poor energy transfer and morphology. The phase distribution n of quasi-2D perovskite can be controlled by adjusting the competition between A site cations and large organic cations. We use octafluoronaphthalene (OFN) as an additive which has a synergy effect with PEABr to slow down the release of PEABr during the process of forming small-n phases after spin coating. The peak external quantum efficiency (EQE) of 6.45% and the optimum luminance of 27,604 cd/m2 were obtained. Our findings provide a fresh sight of adjusting phase distribution through synergy effect with large organic cations.