Facile Room‐Temperature Anion Exchange Reactions of Inorganic Perovskite Quantum Dots Enabled by a Modular Microfluidic Platform

Abstract

In an effort to produce the materials of next-generation photoelectronic devices, postsynthesis halide exchange reactions of perovskite quantum dots are explored to achieve enhanced bandgap tunability. However, comprehensive understanding of the multifaceted halide exchange reactions is inhibited by their vast relevant parameter space and complex reaction network. In this work, a facile room-temperature strategy is presented for rapid halide exchange of inorganic perovskite quantum dots. A comprehensive understanding of the halide exchange reactions is provided by isolating reaction kinetics from precursor mixing rates utilizing a modular microfluidic platform, Quantum Dot Exchanger (QDExer). The effects of ligand composition and halide salt source on the rate and extent of the halide exchange reactions are illustrated. This fluidic platform offers a unique time-and material-efficient approach for studies of solution phase-processed colloidal nanocrystals beyond those studied here and may accelerate the discovery and optimization of next-generation materials for energy technologies.The ORCID identification number(s) for the author(s) of this article can be found under https://doi.org/10.1002/adfm.201900712.to outperform conventional and wellstudied II-VI, IV-VI, and III-V QDs (e.g., CdSe, [7] CdSe/ZnS, [8] PbS, [9] and InP [10] ) in QD-based solar cells [7] and light-emitting diodes (LEDs). [11,12] Perovskite QDs have enabled lower energy consumption and a wider reaching color gamut in QD-based LED displays and unparalleled improvements in photovoltaic power conversion efficiency of QD-based solar cells compared to other third-generation technologies. Recent work [13][14][15] has demonstrated that hybrid perovskite QDs, compared to their thin-film counterparts of equivalent composition, achieve higher open-circuit voltage. The outstanding performance of perovskite QDs can be attributed to their unique optical properties including inherently high charge carrier mobility, long diffusion lengths, high PLQY, and facile bandgap tunability. Moreover, postsynthesis halide exchange of perovskite QDs with halide salts offers an additional degree of control and tunability of the nanocrystal optical properties. [16] Over the last 3 years, various solid-solvent, [17] incompatible solvent-solvent, [18] and homogeneous solution-phase [16] anion exchange strategies have been developed for organic and inorganic perovskite QDs. Among these strategies, homogeneous solution-phase reactions are far more conducive toward continuous nanomanufacturing processes, enabling enhanced parameter control and multidimensional tunability. Further development and implementation of these materials could potentially result in more effective energy technologies toward addressing ever-growing global energy demands via low-cost, high-efficiency solar energy harnessing solutions.Conventionally, manual flask-based techniques have been the primary approach for the synthesis, characterization, and optimization of colloidal QDs. However, the time-and mate...

Methanol-induced fast CsBr release results in phase-pure CsPbBr3 perovskite nanoplatelets

“…[1][2][3][4][5] Showing high photoluminescence (PL) quantum yields (QYs), 6,7 an optimal range of band gap energy values and high defect tolerance, [8][9][10][11] the perovskite nanomaterials hold great promise for solar cell, 12 photodetector, 13 laser, 14,15 light-emitting diode (LED) and display applications. [16][17][18][19][20][21][22][23][24][25][26][27][28][29][30] Being free from the organic component, the all inorganic CsPbX 3 (X À stands for halide ions) perovskites are compositionally stable up to their melting points which are in excess of 460 C, 31 and thus have attracted enormous interest.…”

Role of Capped Oleyl Amine in the Moisture‐Induced Structural Transformation of CsPbBr3 Perovskite Nanocrystals

“…These interesting properties of perovskites are mainly due to their peculiar crystal structures . Thus, any alteration in the crystal structure can vary the optoelectronic properties of perovskites . Even though perovskites have many advantages, stability under ambient conditions is its major limitation .…”

“…[27,28] Thus, any alteration in the crystal structure can vary the optoelectronic properties of perovskites. [29,30] Even though perovskites have many advantages, stability under ambient conditions is its major limitation. [2,[31][32][33] Moisture or higher temperature can decompose CsPbBr 3 to PbBr 2 .…”

Continuous Synthesis of Nanocrystals via Flow Chemistry Technology

“…Meanwhile, online detections helped to optimize the synthesis reaction based on few sample parameters . Recently, Abolhasani et al developed a tubular flow chemistry platform to synthesize high‐quality perovskite nanocrystals . CsPbX 3 with different halogen doping ratios were prepared by changing the concentration of precursor halide salt and the ligand ratio, as shown in Figure c.…”

“…c) UV‐illuminated snapshots of the continuous anion exchange reactions of CsPbBr 3 QDs and TEM images of the perovskite. Reproduced with permission . Copyright 2019, Wiley‐VCH.…”