Spontaneous Silver Doping and Surface Passivation of CsPbI₃ Perovskite Active Layer Enable Light-Emitting Devices with an External Quantum Efficiency of 11.2%

Abstract

Lead halide perovskite nanocrystals are currently under intense investigation as components of solution-processed light-emitting devices (LEDs). We demonstrate LEDs based on Ag doped–passivated CsPbI3 perovskite nanocrystals with external quantum efficiency of 11.2% and an improved stability. Ag and trilayer MoO3/Au/MoO3 structure were used as cathode and anode, respectively, which reduce the electron injection barrier and ensure the high transparency and low resistance of the anode. Silver ions diffuse into perovskite film from the Ag electrode, as confirmed by the elemental mapping, the presence of Ag 3d peaks in the X-ray photoelectron spectrum, and the peak shift in the X-ray diffraction patterns of CsPbI3. In addition to doping, silver ions play the beneficial role of passivating surface defect states of CsPbI3 nanocrystals, which results in increased photoluminescence quantum yield, elongated emission lifetime, and improved stability of perovskite films.

Unveiling the Photo‐ and Thermal‐Stability of Cesium Lead Halide Perovskite Nanocrystals

“…CsPbX 3 nanocrystals have been incorporated into solar cells achieving a record 13.4 % power conversion efficiency (PCE). [15] Other syntheses have expanded this general idea by generating multiple nanocrystal morphologies through ligand mediation [21][22] and reaction tuning, [23] by using different surface ligands for improved quantum yields, [24][25] by increasing surface passivation/repair via salt solutions, [26][27][28][29] as well as by generating other cation/anion compositions through doping [17,[30][31][32][33][34][35] or post-synthetic ion exchange. [12,[19][20] Most reported syntheses of CsPbX 3 follow the work of Protesescu et al who demonstrated a simple, solution-based synthesis for nanocrystals with high luminescence.…”

“…[59] Importantly, the δ phase for CsPbI 3 is nonluminescent, rendering the material unusable for most applications. [17,65] A recent report by Liao et al describes the thermal stability of cesium lead halide perovskites from À 190 to 500°C using Raman spectroscopy and XRD. [52] Liu and coworkers compare CsPbI 3 nanocrystals stabilized with trioctylphosphine (TOP) to those stabilized with oleic acid and oleylamine.…”

Yb3+ and Yb3+/Er3+ doping for near-infrared emission and improved stability of CsPbCl3 nanocrystals

“…17,18 In fact, many reports have validated the facile doping in lead halide perovskites due to their non-rigid structures. For example, Ag + , K + , Rb + , Sn 4+ , Sn 2+ , Zn 2+ , Cd 2+ , Bi 3+ and Mn 2+ have been applied as dopants, 19–26 but none of them can enable near-infrared (NIR) emissions.…”

Metal halide perovskite nanocrystals and their applications in optoelectronic devices

“…), B site doping (with Mn 2+ , Ni 2+ , Sn 4+ , Ln 3+ , etc. ), surface engineering, matrix encapsulation, and postprocessing …”

“…), 256 B site doping (with Mn 2+ , Ni 2+ , Sn 4+ , Ln 3+ , etc. ), [257][258][259][260][261][262][263][264] surface engineering, 195,197 matrix encapsulation, 196,265 and postprocessing. 161,266,267 Coupled with lattice incompleteness, many defects are presented in these NCs, including Schottky defects (cation and anion vacancies), Frenkel defects (interstitial sites), inversion defects, and structural defects (grain boundary, interface, and lattice distortion caused by impurities).…”