Improving the Operational Stability of Near‐Infrared Quasi‐2D Perovskite Light‐Emitting Diodes by Cation Engineering

Abstract

their operation stability is still far from the industrial standard, impeding their commercialization. [11] Ion migrations inside perovskites are a vital issue that undermines the operation stability of PeLEDs. [12,13] Various strategies have been employed to mitigate the negative effects of mobile ions, including the use of molecular additives, [14,15] metal doping, [16,17] and interfacial engineering. [18,19] Previous studies have revealed that PeLEDs with enhanced efficiency stability can be achieved by incorporating organic longchain cations into precursors to form quasi-2D Ruddlesden-Popper halide perovskites. [20][21][22] Theoretical calculations demonstrated that bulky organic cation layers between inorganic octahedral sheets in quasi-2D perovskites increase the defect formation energies of perovskites, acting as ion migration barriers to suppress ion migration and drastically enhance the operational stability of PeLEDs. [23][24][25] However, iodide ions in the FAPbI 3 lattice have lower activation energies and are more likely to migrate, [26,27] and the operational stability Although organic metal halide perovskite light-emitting diodes (PeLEDs) have been developed rapidly in recent years, their commercialization and further applications are still hindered by ion migration-induced inferior operational stability. Although the formation of a quasi-2D structure is a well-known solution that can efficiently suppress ion migration, the operation lifetime improvement is still limited. In this study, long-chain phenylbutanammonium is used to replace the commonly used phenethylammonium as the L-site cations. With large steric hindrance, ion migration inside the PeLEDs is effectively suppressed. Consequently, the PeLED with near-infrared emission at 763 nm exhibited an operational lifetime (T 90 ) of up to 5.3 h, which is 53-fold higher than that of the control device. This study demonstrates the feasibility of significant stability improvement using a simple cation engineering strategy for PeLEDs.

Improving Perovskite Green Quantum Dot Light-Emitting Diode Performance by Hole Interface Buffer Layers

“…Characterizations. Our work's characterization methods and devices are consistent with those described in our previous work, 30 including absorption of QD films; PL, TRPL, and PLQY measurements; and electrical characteristics and performance measurements of QLED devices.…”

“…High defect density generates a large accumulation of charged ions inside the devices, which are the key factors that impede the operational stability of perovskite QLED devices. 30,33 In the two buffer layer materials we selected, PMMA and PVP, the carbonyl group in the molecular structure can combine with uncoordinated Pb 2+ ions to achieve the passivation of the perovskite interface. We performed capacitance−frequency (C−F) measurements on the devices to the accumulation of ions at the interface.…”

“…The calculated defect density of the pristine QD films is 3.27 × 10 17 cm –3 , while the defect density of the QD films added with PMMA and PVP as the bottom interface buffer layer is 1.83 × 10 17 and 2.65 × 10 17 cm –3 , respectively, which are significantly lower than the pristine QD film. High defect density generates a large accumulation of charged ions inside the devices, which are the key factors that impede the operational stability of perovskite QLED devices. , In the two buffer layer materials we selected, PMMA and PVP, the carbonyl group in the molecular structure can combine with uncoordinated Pb 2+ ions to achieve the passivation of the perovskite interface. We performed capacitance–frequency (C–F) measurements on the devices to the accumulation of ions at the interface .…”

Ammonium Thiocyanate Enhanced High-Performance Quasi-Two-Dimensional Perovskite Solar Cells

“…The excellent optical and photoelectrical properties of perovskite, such as its high absorption coefficient, long carrier diffusion length, and simple solution process, have contributed to its emerging application in photovoltaic technology. − Quasi-two-dimensional (Q2D) perovskite solar cells have shown not only potential superstability but an impressive power conversion efficiency (PCE) of over 22.26% as well. − The impressive efficiency has shed light toward future commercial applications, while further improvement on the performance of Q2D PSCs is still in demand compared to those of other PSC counterparts. − …”