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

作者：Chen, Chiung-Han; Kuo, Yen-Hung; Lin, Yu-Kuan; Ni, I-Chih; Lin, Bi-Hsuan; Wu, Chih-I; Yip, Hin-Lap; Kuo, Chi-Ching^*; Chueh, Chu-Chen^*

来源：ACS applied materials & interfaces, 2022, 14(7): 9587-9596.

DOI：10.1021/acsami.1c23594

• light-emitting diodes
• quasi-2D perovskite
• natural cyclic molecules
• phase regulation
• color purity

In this study, two natural small molecules, alpha-cyclodextrin (alpha-CD) and beta-cyclodextrin (beta-CD), are used as additives to improve the performance of quasi- 2D PEA(2)Cs(n-1)Pb(n)Br(3n+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 alpha-CD effectively suppresses the formation of the low-n phases (n = 2), while beta-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 a-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 beta-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 alpha-CD- and beta-CD-based PeLEDs, respectively, and EQE is enhanced by similar to 4.8 times for both devices; besides, both CD-assisted devices also exhibit improved color purity and a lower bias dependency of electroluminescent intensity.