Surface Modification of ZnO Nanocrystals with Conjugated Polyelectrolytes Carrying Different Counterions for Inverted Perovskite Light-Emitting Diodes

Abstract

In this work, bromide ions (Br–) on the conjugated polyelectrolytes (CPEs) were converted to tetrafluoroborate (BF4 –) or hexafluorophosphate (PF6 –) ions through anion exchange. The three CPEs (PFN-Br, PFN-BF4, and PFN-PF6) were utilized solely for surface modification of zinc oxide nanocrystals (ZnO NCs). The ionic groups on CPEs can form permanent dipoles to facilitate charge injection from ZnO NCs to cesium lead bromide (CsPbBr3) NC emitters, therefore promoting luminescent properties of inverted perovskite light-emitting diodes (PeLEDs). The experimental results reveal that ZnO NC films were smoothened by CPEs that allowed flat deposition of the perovskite active layers; moreover, the improved contact between ZnO and perovskite layers was beneficial for reducing leakage current, as verified in the dark current measurement of devices. In addition, the incorporation of CPEs helped to passivate the defects of ZnO NC films and prolong the carrier lifetime of CsPbBr3 NCs. PeLEDs based on different CPEs were then constructed and evaluated. The device based on PFN-Br showed the highest brightness and current efficiency, and the one based on PFN-BF4 exhibited better current efficiency over PFN-Br under the low current density below 160 mA/cm2. This is the first report using fluorene-based CPEs with Br–, BF4 –, or PF6 – groups to modify the properties of ZnO and CsPbBr3 NCs for the construction of inverted PeLEDs so far. Our experiments explored new kinds of CPEs on the surface modification of ZnO NCs and device performance of PeLEDs.

All-inorganic lead halide perovskites for photocatalysis: a review

“…The surface modification of all-inorganic lead halide compounds, 210,211 such as ligand modification, 212–214 can also increase their stability and photocatalytic performance. Surface ligands play a key role in forming perovskites, which not only affect the nucleation and growth processes but are also extremely important for charge transport and structural stability.…”

Interfacial Regulation toward Efficient CsPbBr3 Quantum Dot-Based Inverted Perovskite Light-Emitting Diodes

“…23,24 Besides, organic halide salt, such as phenethylammonium bromide (PEABr) and PFNBr, has also been developed to facilitate the recrystallization of perovskite films. 25,26 As a result, the photoluminescence quantum yield (PLQY) is enhanced. A substantial increase in device efficiency is achieved in the above-reported method.…”

“…However, in PeLEDs, especially for the normal structure devices, the deprotonation reaction of the ammonium cations at the ZnO/perovskite interface can induce the decomposition of perovskites and favorable solution-processing ZnO with nonpolar solvents can induce the destruction and redissolution of the underlying perovskite film, resulting in low photoluminescence efficiency and electroluminescence performance. ,, Several strategies have been widely reported to determine the influence of ZnO on the perovskite film. Organic polyvinylpyrrolidone (PVP) and magnesium (Mg) doping are commonly used to passivate the surface defects of ZnO NPs and improve the morphology and stability of upper perovskite films, contributing to the suppressed nonradiative recombination. , Besides, organic halide salt, such as phenethylammonium bromide (PEABr) and PFNBr, has also been developed to facilitate the recrystallization of perovskite films. , As a result, the photoluminescence quantum yield (PLQY) is enhanced. A substantial increase in device efficiency is achieved in the above-reported method.…”

Heterojunctions of Mercury Selenide Quantum Dots and Halide Perovskites with High Lattice Matching and Their Photodetection Properties

“…It was not until 2003 that researchers such as Green [11] and subsequently Piepenbrock [12] employed metal salts and organic media for quantum dot synthesis, markedly enhancing the monodispersity and size uniformity of the quantum dots, while concurrently rendering the synthesis process more safe and straightforward. Nonetheless, CQDs synthesized via organic media are characterized by surfaces adorned with extensive long carbon chain ligands, including, but not limited to, oleic acid, oleylamine, and tributyl phosphate, which markedly impede the charge carrier transport within films, thereby precipitating a reduction in the efficiency of quantum dot optoelectronic devices [13]. Thus, it is essential to modify the surface of CQDs for improving the electrical properties.…”