Domain Controlling by Compound Additive toward Highly Efficient Quasi‐2D Perovskite Light‐Emitting Diodes

Abstract

Quasi-2D perovskites with enlarged exciton binding energy and tunable bandgap are appealing for application in perovskite light-emitting diodes (PeLEDs). However, wide n domains distribution is commonly formed in solution-processed quasi-2D perovskite films due to the uncontrollable crystallization behavior, which leads to low device performance. Here, the crystallization process is successfully regulated to narrow the n domains distribution by introducing compound additive of ZrO 2 nanoparticles (NPs) and Cryptand complexant. ZrO 2 NPs can avoid the segregation of organic large and small cations by strengthening the solvent extraction capacity of antisolvent, while Cryptand offsets the poor solubility of PbBr 2 by forming an intermediate state to slow down the crystallization of high-n domains. Consequently, both high photoluminescence quantum yields over 90% and a high external quantum efficiency of 21.2% are obtained in the optimized green quasi-2D PeLEDs. Moreover, the lifetime extends about four times compared with control devices. The strategy of domain controlling by compound additive provides a powerful way to develop high-performance quasi-2D perovskite optoelectrical devices.

Engineering of Annealing and Surface Passivation toward Efficient and Stable Quasi-2D Perovskite Light-Emitting Diodes

“…As the annealing time is extended, the τ value shows an upward trend, while the PLQY of the quasi-2D perovskite film decreases from 78.01 to 72.17, 72.12, and 62.60% in turn, as shown in Figure c. On the basis of the results above, we calculate the radiative and nonradiative recombination rates ( k r , k nr ) of the quasi-2D perovskite films according to the equation PLQY = k r /( k r + k nr ) and τ = ( k r + k nr ) −1 . ,, As shown in Figure d, when the annealing time increases from 5 to 20 min, k nr changes very little, while k r exhibits an apparent downward trend. This should be due to the crystal transformation during annealing.…”

“…Lead halide perovskites have received extensive attention in the field of light-emitting diodes (LEDs) due to their efficient radiative recombination, wide luminous color gamut, and high color purity. − The quasi-two-dimensional (quasi-2D) perovskite with a self-assembled multiple quantum wells (QWs) structure proves to be one of the great light emitters, which possesses high exciton binding energy ( E b ) and an efficient energy-funnel effect that appealing to application in perovskite light-emitting diodes (PeLEDs) and lasers. − The PeLEDs based on quasi-2D perovskites have obtained remarkable external quantum efficiencies (EQEs) of >20% for green and red PeLEDs and 10% for blue devices. − Meanwhile, the efficient quasi-2D perovskite emitters can be prepared by simple one-step solution processing and demonstrate great potential for low-cost and flexible lighting and display. During solution processing, thermal annealing is an indispensable procedure in the preparation of perovskite films to remove residual solvent and promote crystallization.…”

Phosphonate/Phosphine Oxide Dyad Additive for Efficient Perovskite Light‐Emitting Diodes

“…[7][8][9][10][11] Among neutral additives, small molecules containing -NH 2 , CÀ OÀ C, C=O, P=O functional groups have been studied. [12][13][14][15][16][17][18][19] For example, amine-functionalized molecular additives were demonstrated to increase the defect passivation effect by reducing the hydrogen bonding between -NH 2 group and FA + (FA, formamidinium). [12] Recently, fluorinated triphenylphosphine oxide (TFPPO) with a P=O group chemically coordinating with unsaturated Pb was reported to suppress defects.…”

Phosphonate/Phosphine Oxide Dyad Additive for Efficient Perovskite Light‐Emitting Diodes

“…Introduction of additives is an important strategy to improve the device efficiency of PeLEDs, and they can be divided into ionic and neutral ones [7–11] . Among neutral additives, small molecules containing ‐NH 2 , C−O−C, C=O, P=O functional groups have been studied [12–19] . For example, amine‐functionalized molecular additives were demonstrated to increase the defect passivation effect by reducing the hydrogen bonding between ‐NH 2 group and FA + (FA, formamidinium) [12] .…”