Novel Lewis Base Cyclam Self-Passivation of Perovskites without an Anti-Solvent Process for Efficient Light-Emitting Diodes

Abstract

Metal halide perovskites have been focused as a candidate applied as a promising luminescent material for next-generation high-quality lighting and high-definition display. However, as perovskite films formed, high density of defects would be produced in solution processing inevitably, leading to low exciton recombination efficiency in light-emitting diodes (LEDs). Herein, a facile and novel self-passivation strategy to inhibit defect formation in perovskite films for constructing high-performance LEDs is developed. For the first time, we introduce 1,4,8,11-tetraazacyclotetradecane (cyclam) in perovskite precursor solution, and it spontaneously passivates defect states of CsPbBr3-based perovskites by coaction between amine and uncoordinated lead ions during spin-coating without an anti-solvent process. Furthermore, as a delocalized system, cyclam also possesses chemical properties that facilitate exciton transportation. The proposed passivation strategy boosts the external quantum efficiency from 1.25% (control device) to 16.24% (cyclam-passivated device). Furthermore, defect passivation is also conductive to reduce LED degradation paths and improve device stability as the extrapolated lifetime (T 50) of LEDs at an initial brightness of 100 cd/m2 is increased from 0.9 to 127 h. These findings indicate that the introduction of cyclam is highly effective to enhance the performance of LEDs, and such a strategy in effectively reducing the defects could be also applied in other perovskite-based devices, such as lasers, solar cells, and photodetectors.

Dual Passivation Strategy for High Efficiency Inorganic CsPbI2Br Solar Cells

“…The increased binding energy tells a changed environment of [PbI 6 ] 4− and [PbBr 6 ] 4− octahedra, which is corresponding to the shrinkage of the octahedra to stabilize the crystal structure of CsPbI 2 Br. [ 30 ] Furthermore, the binding energy of C 1s at 292.9 eV appears ( Figure a), which is related to the π − π bonding in the phenyl functional group of the PEA + cations. [ 28 ] The appearance of the PEA + signal suggests the formation of PEA + related low‐dimensional perovskite on the surface of the CsPbI 2 Br.…”

State of the Art and Prospects for Halide Perovskite Nanocrystals

“…Somewhat related, Hassan et al 408 have shown the beneficial effect of multidentate ligands to passivate effectively perovskite NCs, thus preventing halide segregation in I/Br mixed-halide perovskite LEDs under electroluminescent operation. Moreover, Han et al 409 have recently applied the Lewis base cyclam (1,4,8,11-tetraazacyclotetradecane) as an effective, self-sufficient passivation, multichelating ligand of perovskite NCs, thus boosting the performance of light-emitting diodes (external quantum efficiency (EQE) of 16.24%). These results are encouraging and give clues on the nature of the ligands needed to enhance the charge injection and transport at the interface of the passivated perovskite surfaces.…”

Perovskite Light‐Emitting Diodes with EQE Exceeding 28% through a Synergetic Dual‐Additive Strategy for Defect Passivation and Nanostructure Regulation

“…[5][6][7][8] To improve the efficiency and stability of PeLEDs, several strategies have recently been adopted such as forming quasi-core/shell structure by antisolvent crystallization, passivating perovskite defects by small molecules or polymers, and constructing quasi-2D perovskite by reducing crystal size. [9][10][11][12] These approaches have successfully enhanced external quantum efficiencies (EQEs) of PeLEDs, achieving up to 23.4% for green light emission and 21.6% for near-infrared light emission. [13,14] Although the above strategies significantly increased the efficiency, there are still many unsolved problems.…”