Perovskite Quantum Dots: Transforming the Landscape of Optoelectronics

Over the past 15 years, perovskite quantum dots (PQDs) have emerged as an interesting class of quantum materials. These metal halide perovskite nanoscale structures have garnered attention due to their exceptional optoelectronic properties, high photoluminescence quantum yields (PLQY), size-tunable emission spectra, and high defect tolerance. These properties make PQDs ideal for applications ranging from light-emitting diodes (LEDs) to solar cells and next-generation display technologies.

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What Makes Perovskite Quantum Dots Unique?

Perovskite quantum dots derive their unique properties from their hybrid organic-inorganic structure and quantum confinement effects. The basic formula of these quantum dots is ABX₃, where 'A' is typically an organic or inorganic cation, 'B' is a metal (commonly lead), and 'X' is a halide anion. Perovskite nanocrystals are synthesized as colloids, which can be classified as quantum dot (0D), nanowire (1D), or nanoplatelet (2D) materials. Some perovskites are much more stable on the quantum scale, so they lend themselves well to being used in quantum dot formation rather than as a bulk 3D crystal. This includes CsPbX3 perovskite, which is very resistant to moisture and oxygen degradation.

Perovskite quantum dots have very strong emission properties. The quantum confinement effect causes perovskite QDs to exhibit a size-dependent bandgap, allowing them to absorb and emit light over a wide range of wavelengths. ​(Meng 2019, Huang 2022).

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One of the standout features of PQDs is their high photoluminescence quantum yield (PLQY). Some perovskite quantum dots exhibit PLQY values exceeding 95%, making them extraordinarily efficient in emitting light when excited by photons ​(Meng 2019, Dai 2017). This high efficiency, combined with their tunable emission across the visible spectrum, opens the door for their use in color displays, high-performance LEDs, and efficient solar cells.

Perovskite Quantum Dots in Solar Cells

Perovskite quantum dots can be used in various solar cell technologies to improve the light absorption and energy conversion of other solar cells. For example, PQDs have been employed as luminescence downshifting (LDS) layers in both silicon and perovskite solar cells to capture high-energy photons from the UV-blue region of the solar spectrum and re-emit them as lower-energy photons that silicon can absorb more efficiently (Meng et al. 2019, Chen et al. 2019, Akin 2019). Introducing perovskite quantum dot layers can also enhance charge transport between layers in photovoltaic devices, improving solar cell performance.

Optoelectronic Applications Beyond Solar Cells

Perovskite quantum dots also hold significant promise in light-emitting diodes (LEDs). Their high color purity, combined with their size-tunable emission, could allow the production of vibrant, energy-efficient displays. PQD-LEDs have shown external quantum efficiencies (EQE) that rival or exceed those of traditional quantum dot-based LEDs.

In addition, PQDs are being explored for use in lasers, whose narrow emission linewidth and high PLQY make them ideal for low-threshold, high-efficiency laser devices. The tunable emission of perovskite quantum dots also allows for their integration into photodetectors, medical imaging, and other optoelectronic applications ​(Dai 2017, Huang 2022).

Synthesis of Perovskite Quantum Dots

One of the benefits of perovskite quantum dots is that they are quite easily synthesized. One method of doing this can be done at room temperature in air by vigorously stirring the precursor components and capping ligands in a good solvent, then pouring this solution into a poor solvent. The perovskite quantum dot separates from the solution within seconds.

Another method of producing perovskite QDs is hot injection, where precursors such as lead halides and cesium salts are rapidly injected into a high-temperature solvent, forming nanocrystals. This technique offers precise control over the size and shape of the quantum dots, which in turn allows for fine-tuning their optical properties.

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Hot injection synthesis should be done under inert conditions such as a schlenk line or within a glove box.

Stability and Challenges

Despite their numerous advantages, perovskite quantum dots face challenges related to stability. PQDs are highly sensitive to moisture, oxygen, and thermal conditions, which can lead to degradation over time. Researchers actively explore various encapsulation techniques and surface treatments to improve environmental stability. Additionally, efforts are ongoing to replace lead-based perovskites with more environmentally friendly alternatives.

The Future of Perovskite Quantum Dots

As research into perovskite quantum dots advances, their potential applications are expanding into areas such as quantum computing, single-photon sources, and next-generation displays. With continued improvements in synthesis methods, stability, and scalability, perovskite quantum dots are poised to play a pivotal role in the future of optoelectronics.

References

1. Meng, L. et al. (2019) ‘Improving the efficiency of silicon solar cells using in situ fabricated perovskite quantum dots as luminescence downshifting materials’, Nanophotonics, 9(1)
2. Chen, L.-C. et al. (2019) ‘Enhanced efficiency of MAPbI3 perovskite solar cells with FAPbX3 perovskite quantum dots’, Nanomaterials, 9(1)
3. Dai, S. et al. (2017) ‘Perovskite quantum dots with near Unity Solution and neat‐film photoluminescent quantum yield by novel spray synthesis’, Advanced Materials, 30(7).
4. Huang, C.-Y. et al. (2022) ‘Inorganic halide perovskite quantum dots: A versatile nanomaterial platform for electronic applications’, Nano-Micro Letters, 15(1).

This information has been sourced, reviewed and adapted from materials provided by Ossila Ltd.

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