Less-ordered phase distribution of quasi-2D perovskites for deep-blue light-emitting diodes enabled by a deep eutectic solvent

Attributed to pinhole-free morphology, large exciton binding energy and cascade energy transfer, quasi-2D perovskites are highly desirable for efficient blue perovskite light-emitting diodes (PeLEDs). Besides fine con-trol over the n values and its distributions, phase distribution along the vertical direction plays a crucial role in producing high-performance quasi-2D PeLEDs, whether vertically ordered phase distribution or uniform phase distribution. Herein, we introduce an effective strategy to optimize the quasi-2D perovskite phase composition and its distribution along the vertical direction via a kind of deep eutectic solvent (DES). On the one hand, it benefits to minimize the n = 1 phases. On the other hand, its incorporation can modulate the order of the nucleation of different-n phases to yield a less-ordered phase distribution along the vertical direction. As a result, the as-prepared perovskite shows enhanced photoluminescence efficiency and reduced defects. The resulting PeLED yields efficient deep-blue emission with a EQEmax of 1.51% along with a CIE coordinate of (0.134, 0.062), and simultaneously improved spectral stability.