Tailoring Phase Distribution of Quasi‐2D Perovskites via Taurine‐Assistance Enables Efficient Blue Light‐Emitting Diodes

Abstract

Quasi‐2D (Q‐2D) perovskites with typical varied n‐phase structures deserve promising candidates in pursuing high‐performance perovskite light‐emitting diodes (PeLEDs). Whereas their weakness in precise n‐phase distribution control disables the optical property of PeLEDs since the n = 1 phase is dominated by severe nonradiative recombination. Here, an effective phase distribution tailoring strategy is developed for pure blue PeLEDs by introducing taurine (TAU) into mixed halide Q‐2D perovskites. The sulfonic acid group in TAU can coordinate with Pb2+ to suppress the formation of the n = 1 phase while promoting the growth of Q‐2D perovskites into domains with the graded distribution of n = 2 and 3. The amino group in TAU forms hydrogen bonds with electronegative halide ions, suppressing the formation of halide vacancies and reducing the defect density in the Q‐2D perovskite films. As a result, optimized blue Q‐2D perovskite films boosted PLQY to 92%. Target blue PeLED was endowed with a peak EQE of 14.82% (average 12.6%) at 475 nm and a maximum luminance of 1937 cd m−2, which is among the reported high‐level pure blue PeLEDs. This work demonstrates a feasible approach to regulate the phase distribution of Q‐2D perovskites for high‐performance blue PeLEDs.

Energy Transfer-Dominated Quasi-2D Blue Perovskite Light-Emitting Diodes

“…The evidence points to the fact that while the ligands can hinder ion migration to some extent by passivating defects, the phase distribution plays a crucial role by allowing efficient energy transfer in the EL performance of quasi-2D perovskite devices. We speculate that efficient energy transfer from low-n phases ( n = 2 and n = 3 phases) to large-n phases is favorable for improving device performance in quasi-2D perovskites …”

“…We speculate that efficient energy transfer from low-n phases (n = 2 and n = 3 phases) to large-n phases is favorable for improving device performance in quasi-2D perovskites. 50 To confirm the above hypothesis, the femtosecond (fs) timeresolved transient absorption (TA) measurements were utilized to evaluate the influence between DBA and SFB molecules on the phase distribution and the carrier transfer dynamics for the Therefore, the TA dynamics with a fast and a slow time decay component were obtained from the TA spectra to further elucidate exciton formation and carrier recombination. The kinetic curves were fitted by using a multiexponential function:…”

Effective Small Organic Molecule as a Defect Passivator for Highly Efficient Quasi‐2D Perovskite Light‐Emitting Diodes

“…These characteristics are advantageous for the performance of the devices and have the potential to reduce the leakage current in PeLEDs. [46,47] Besides, the bright spots on the AFM images are speculated to be the PbBr 2 crystal, [47] and the decreased quantities of them could indicate the decrease of the uncoordinated Pb 2+ ions defects.…”

“…This phenomenon indicates that diBDF only acts as the ligand to coordinate with Pb 2+ and does not enter the crystal lattice. [47] The steady-state PL results for the perovskite film, both with and without diBDF, are depicted in Figure 3a. The perovskite film containing the diBDF compound demonstrates a notable increase in PL intensity.…”