Superior External Quantum Efficiency of LEDs via Quasi-2D Perovskite Crystals Implanted with Phenethylammonium Acetate

Abstract

The multiple quantum well structure of a quasi-twodimensional (quasi-2D) perovskite leads to nonradiative Auger recombination (AR). This is due to high local carrier density in recombination centers, although the radiative recombination is improved by efficient energy transfer. In this study, we suppress the AR by introducing phenethylammonium acetate (PEAAc) into the quasi-2D PEA 2 Cs n−1 Pb n Br 3n+1 perovskite. The recombination centers of n ≥ 4 phases can be promoted because the COO − preferentially coordinates with Pb 2+, inhibiting the fast formation of n = 1, 2, 3 phases with phenethylammonium anion (PEA + ). Thus, the AR is suppressed due to the lower density of local charge carriers. To balance the AR suppression and decreasing binding energy in promoting the n ≥ 4 phases, the PEAAc:PEABr molar ratios are adjusted. At the optimal molar ratio, perovskite light-emitting diodes (PeLEDs) with a maximum luminescence of ∼29942 cd m −2 and a maximum external quantum efficiency of ∼20.2% are achieved. These results confirm the most efficient PeLEDs based on PEA 2 Cs n−1 Pb n Br 3n+1 without passivation. Moreover, the efficiency roll off is significantly mitigated with a high threshold of over 3.51 mA/cm 2 . This study develops high-efficiency PeLEDs with a low efficiency rolloff.

Polycrystalline Lead-Free Perovskite Direct X-Ray Detectors with High Durability and Low Limit of Detection via Low-Temperature Coating

“…These notable outcomes are ascribed to the enhanced film quality stemming from in situ treatment mechanisms (Figure i), wherein Ac – ions effectively coordinate with Bi 3+ and Ag + ions, while PEA + establishes robust hydrogen bonding interactions with halogen species. These orchestrated interactions collectively impede the nucleation rate of Cs 2 AgBiBr 6 , thereby facilitating the subsequent passivation of halogen vacancies and grain boundaries. − The resultant mitigation of grain boundary and halogen vacancy defects contributes to the reduction in defect state density, thereby leading to a reduction in ion migration pathways, abating nonradiative carrier recombination.…”

Efficient pure-red perovskite light-emitting diodes with strong passivation via ultrasmall-sized molecules

“…X-ray photoelectron spectroscopy (XPS) measurements indicate that the core levels of Pb 4f and I 3d exhibit a blue shift of approximately 0.2 eV for the perovskite on the CsFa-added HTL (fig. S7), suggesting that the Pb-I bond of CsFa-added sample is shorter and stronger, resulting in a more stable perovskite lattice structure ( 38 , 39 ). From ultraviolet (UV) photoelectron spectroscopy (UPS), the valence band maximums of the HTLs can be obtained (fig.…”

“…S12, table S3, and note S1) ( 15 , 42 , 43 ). A plausible explanation for the suppression of small- n phase is the steric hindrance, i.e., the coordination of anions (Ac − and Fa − ) with Pb 2+ sites hinders the binding of large L-site organic cations within the perovskite structure ( 38 , 44 ). After exposing the perovskite films grown on different HTLs to ambient air for a duration, PL testing was conducted to assess their stability.…”

High‐Performance Green Quasi‐2D Perovskite Light‐Emitting Diodes via Passivated Defects

“…In recent years, quasi-2D metal halide perovskite materials have demonstrated outstandingly distinct advantages such as large exciton binding energy, [1] high photoluminescence quantum yields (PLQYs), [2][3][4][5] great color purity (half-peak width of 20 nm), [6,7] tunable bandgap (light encompassing the full visible) [8,9] and naturally generated multiple quantum well structure. [10][11][12] These exceedingly distinctive characteristics have propelled research in light-emitting diodes (LEDs), [13][14][15][16][17][18] and solar cells. [19][20][21][22][23] It is noteworthy that external quantum efficiency (EQE), stability, and device luminescence have all been improved tremendously for light-emitting diodes.…”