Enhancing the Performance of Quasi-2D Perovskite Light-Emitting Diodes Using Natural Cyclic Molecules with Distinct Phase Regulation Behaviors.

In this study, two natural small molecules, α-cyclodextrin (α-CD) and β-cyclodextrin (β-CD), are used as additives to improve the performance of quasi-2D PEA 2 Cs n -1 Pb n Br 3 n +1 ( n = 3, herein) PeLEDs. Both of them are shown to efficiently passivate the quasi-2D perovskite films to afford improved film quality and morphology, but they exhibit distinct phase regulation behaviors possibly due to their different pore sizes. It reveals that α-CD effectively suppresses the formation of the low- n phases ( n ≤ 2), while β-CD better regulates the phase with a medium- n value ( n = 3). Because of effectively suppressing the formation of low- n phases, the CD-assisted quasi-2D perovskite films possess facilitated exciton energy transfer and reduced nonradiative recombination. Consequently, the optimized α-CD-derived PeLED shows the highest luminance ( L max ) of 37,825 cd/m 2 with an external quantum efficiency (EQE) of 3.81%, while the β-CD-derived PeLED delivers a lower L max of 24,793 cd/m 2 with an EQE of 3.09%. Compared to the pristine device, L max is enhanced by 6.3 and 3.8 times for α-CD- and β-CD-based PeLEDs, respectively, and EQE is enhanced by ∼4.8 times for both devices; besides, both CD-assisted devices also exhibit improved color purity and a lower bias dependency of electroluminescent intensity.