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About this book

This book addresses perovskite quantum dots, discussing their unique properties, synthesis, and applications in nanoscale optoelectronic and photonic devices, as well as the challenges and possible solutions in the context of device design and the prospects for commercial applications. It particularly focuses on the luminescent properties, which differ from those of the corresponding quantum dots materials, such as multicolor emission, fluorescence narrowing, and tunable and switchable emissions from doped nanostructures. The book first describes the characterization and fabrication of perovskite quantum dots. It also provides detailed methods for analyzing the electrical and optical properties, and demonstrates promising applications of perovskite quantum dots. Furthermore, it presents a series of optoelectronic and photonic devices based on functional perovskite quantum dots, and explains the incorporation of perovskite quantum dots in semiconductor devices and their effect of the performance. It also explores the challenges related to optoelectronic devices, as well as possible strategies to promote their commercialization. As such, this book is a valuable resource for graduate students and researchers in the field of solid-state materials and electronics wanting to gain a better understanding of the characteristics of quantum dots, and the fundamental optoelectronic properties and operation mechanisms of the latest perovskite quantum dot-based devices.

Table of Contents

Frontmatter

Chapter 1. Synthesis of Perovskite Nanocrystals

Abstract
This chapter gives an overview of the synthesis of perovskite nanocrystals. The most commonly used methods are the precipitation method and the injection. Other methods are also mentioned briefly with a few examples.
He Huang

Chapter 2. Strongly Quantum Confined Metal Halide Perovskite Nanocrystals

Abstract
Metal halide perovskite nanocrystals with the chemically tunable bandgap and superb optical properties are promising candidates for a number of high performance optoelectronic and photonic applications. The majority of studies on perovskites have focused on the large perovskite nanoparticles in the weak confinement regime, however recent synthetic advances have allowed for the preparation of high quality 0D, 1D, and 2D confined perovskites, both hybrid organic-inorganic and all-inorganic. These new synthetic methods have enabled the study of confinement effects on various photophysical properties of perovskites nanocrystals previously not possible. In the first section of this chapter, we discuss the synthetic methods for the preparation of both hybrid and all-inorganic perovskite nanocrystals in the strong confinement regime, including the synthetic protocols as well as the mechanistic aspects of the nanocrystal growth. The second section discusses the confinement effects on various static and dynamic photophysical properties of exciton experiencing varying degree and dimensionality of quantum confinement.
Daniel Rossi, David Parobek, Dong Hee Son

Chapter 3. All-Inorganic Perovskite Quantum Dots: Ligand Modification, Surface Treatment and Other Strategies for Enhanced Stability and Durability

Abstract
All-inorganic perovskite CsPbX3 (X = Cl, Br, and I) QDs exhibit outstanding optical performance, including high photoluminescent quantum yield (PLQY), high stability, low Auger recombination loss and large exciton binding energy. However, they suffer from problems related poor humidity and poor thermal stability, which restrict their practical application. In this Chapter, we will focus on the recent advances on the stability of inorganic CsPbX3 QDs. Our review on understanding of the origins of instability and the intrinsic factors affecting their stability are summarized. The various strategies for enhancing the stability of CsPbBr3 perovskite QDs are introduced. Finall, we propose our thoughts on the future development of this field.
Zhigang Zang, Dongdong Yan

Chapter 4. Perovskite Quantum Dots Based Light-Emitting Diodes

Abstract
Beyond the extraordinary success fulfilled in solid-state solar cells, perovskite materials have demonstrated significant potentials in other photonic and optoelectronic devices since 2014. In addition to the perovskite thin films, nanometer-scale perovskite quantum dots (PQDs) with unique optical properties, such as PLQYs approaching unity, high color purity, tunable wavelength, narrow emission bandwidth, and high defect tolerance, have been hotly pursued as promising alternative phosphors in white-light down-converted light-emitting diodes (DC-LEDs) and emitting materials in AM-QLEDs for next-generation lighting sources and displays. In this chapter, the advances in perovskite QDs-based LEDs are reviewed with strategies of material composition design, surface ligand engineering, and device optimization. Besides, the major hurdles for perovskite QLEDs of short lifetime and toxicity (lead-based) are investigated and highlighted; while the solutions undertaken related to surface coating and treatment, device encapsulation, and free-lead perovskite QDs are identified. Moreover, perspectives for the perovskite QDs applied in flexible/stretchable devices and their further development for commercial requirements are also demonstrated.
Yun-Fei Li, Jing Feng, Hong-Bo Sun

Chapter 5. Polarized Emission from Perovskite Nanocrystals

Abstract
Polarization is a fundamental property of light and polarized light, including linearly polarized light, circularly polarized light and elliptically polarized light, plays a very important role in optoelectronic devices and systems, such as liquid crystal display (LCD), labeled biological systems, optical quantum computers, 3D display system, polarization photodetection, etc. Halide perovskites nanocrystals (PNCs), in terms of perovskite quantum dots, nanowires, nanorods, or nanoplates, have been found to demonstrate linearly and circularly polarized luminescence. This chapter provides an overview of the polarized emission mechanism of PNCs and linearly polarized luminescence of PNCs, including several techniques have been developed to align anisotropic PNCs into ordered patterns, for example, electrospinning, mechanical stretching, template assisted growth, solution-phase growth and chemical vapor deposition growth. Finally, the circularly polarized luminescence of PNCs and its potential applications also have been introduced.
Qiang Jing, Kai Wang

Chapter 6. Characterization of Lead Halide Perovskites Using Synchrotron X-ray Techniques

Abstract
In this chapter, we are going to introduce several characterization methods that utilize synchrotron X-rays as the probing source for understanding electronic structure, crystal structure, and optical properties of lead halide perovskite materials. We will show how X-ray absorption fine structure (XAFS) can be used to understand the dissociation mechanism, to identify the presence of defect, and to analyze the influence of dopant introduction on structural modification. We will demonstrate that an X-ray excited optical luminescence (XEOL) in combination with XAFS analysis helps to understand the luminescence mechanism of doped perovskite. We will also present the use of synchrotron X-ray diffraction (XRD) to study the creation of new crystal phases induced by high pressure and the phase transformation of perovskite in situ. The working principle of each technique will be introduced, followed by examples from recently published research articles.
Lijia Liu, Zhaohui Dong

Chapter 7. Perovskite Quantum Dot Photodetectors

Abstract
In this chapter, we will review the developments of perovskite photodetectors in recent years. The application of perovskite nanomaterials—especially perovskite quantum dots (perovskite QDs)—in photodetectors. In Sect. 7.1, the background of perovskite QDs, and photodetectors are introduced. In Sect. 7.2, fundamentals of QD (beyond perovskite QD) photodetectors including their brief history are outlined. In Sect. 7.3, the perovskite based photodetectors, especially the perovskite QD photodetectors, are expounded in different categorizations on the detecting band type, working mechanism, mechanical performance, response feature, device structure, response wavelength and material design. The future of perovskite QD photodetectors is prospected in the last section.
Xiangxing Xu, Linwei Yu

Chapter 8. Perovskite Quantum Dots Based Luminescent Solar Concentrators

Abstract
Luminescent solar concentrators (LSCs) are emerging technology of current interest as a platform for solar energy harvesting. LSCs can serve as large-area sunlight collectors for photovoltaic cells to reduce the cost of electricity by decreasing the use of expensive photovoltaic materials. Among various types of fluorophores, perovskite quantum dots have been used as light-converters due to their size/shape/composition-tunable wide absorption spectrum, narrow emission spectrum, high quantum yield and structure-engineered large Stokes shift. In this Chapter, we summarized the use of various types of perovskites and different configuration to fabricate high efficiency and large-area LSCs. The optical properties of perovskite are strongly depending on their size, shape and composition. Therefore, one can optimize their structure to obtain the suitable emitters for LSCs. Among various types of perovskites, doped quantum dots offer a great opportunity to synthesize high quality perovskites with both high quantum yield and large Stokes shift, indicating the doped perovskites may be a great candidate as emitters for high efficiency LSCs. We conclude with a detailed account of the latest research progress in synthesis, structure, materials, and performance of LSCs based on perovskite quantum dots and a further perspective on the remaining key issues and open opportunities in the field.
Haiguang Zhao

Chapter 9. Perovskite Quantum Dots for Photovoltaic Applications

Abstract
Perovskite solar cell with easy solution processing and high efficiency has been considered as a promising photovoltaic technology, but the material instability makes it questionable for practical applications. Perovskite quantum dots (QDs) provide new possibilities to resolve these concerns. In this chapter, we will discuss the backgrounds, fundamentals, synthesis methods and device physics of the perovskite QDs based solar cells.
Xu Chen, Siyuan Huang, Yue Tian, Tingming Jiang, Yang (Michael) Yang

Chapter 10. Perovskite Quantum Dots Based Phototransistors

Abstract
Perovskite semiconductors have attracted intensely advancing researches in optical devices, due to the long diffusion length, high quantum efficiency and excellent light absorption coefficients and so on. Especially combined with Quantum dots (QDs), this blended semiconductor can be selected as the alternative candidate for the photosensing core of the sensors and other optoelectronics. To realize the incident light-to-electric converting and directly signal’s reading-out, we have put enormous efforts to design and fabricate a versatile phototransistor. The optimal device’s structure also balances the electrical and optical performances to enable enhancing the photodetecting efficiency and compatibility. In this report we reviewed realizations, models, physics and metrology applications of perovskite and perovskite QDs based phototransistor. In our research group, we have designed the phototransistors with QDs as sensing core by nano-manufacturing technology and explored the photo-generation mechanism. The corresponding protocols focus on understanding of connection between these different structures and photodecting performances. The subsequent optimized studies advance technologies for integrated photodetecting applications with potentially inorganic nano-scale optical materials.
Xiang Liu, Yuan Tao, You Zhang, Zhi Tao, Jianhua Chang

Chapter 11. Perovskite Quantum Dots Based Lasing-Prospects and Challenges

Abstract
Since the first report of stimulated emission (SE) and lasing action from colloidal perovskite quantum dots (Pe-QDs) in 2015, Pe-QDs have made great strides in constructing high-performance optically pumped lasers. By virtue of the quantum confinement effect and merits of halide perovskites, the Pe-QDs hold the promise for developing practical and cost-effective lasers based on optical pumping and even electrical injection. In this Chapter, the status and prospects of Pe-QD lasers are introduced. First of all, we present the basic photophysics of Pe-QDs that benefits light emission and SE. Then, the underlying gain mechanisms are discussed. We comprehensively introduce the emerging kinds of Pe-QD lasers based on various high-quality optical resonators. At last, we point out the existing challenges toward the development of high-performance lasers utilizing the Pe-QDs and research trends of Pe-QD lasers in the future.
Yue Wang, Siyang Xia

Chapter 12. Electrospun Nanofibers Embedded with Perovskite Quantum Dots

Abstract
Because of their tunable bandgap, wide visible emission wavelength, and high photoluminescence quantum yield and mobility, perovskite quantum dots (PQDs) have potential in various applications, such as in light emitting diodes, sensors, and photodetectors. However, the poor phase stability of PQDs in the environmental atmosphere impedes their further application. Therefore, encapsulation is important because it enhances PQD stability, with electrospinning (ES) being a versatile encapsulation method. This study investigated recent developments in ES-encapsulation size confinement for organic/inorganic hybrid OIPQDs (CH3NH3PbX3; X = Cl, Br, I) and inorganic IPQDs (CsPbX3; X = Cl, Br, I). ES fibrous systems greatly decrease perovskite size while retaining their shape and without forming aggregates; this facilitates superior photoluminescence (PL) emissiveness and stability.
Manikandan Venkatesan, Loganathan Veeramuthu, Fang-Cheng Liang, Chia-Jung Cho, Chi-Ching Kuo

Chapter 13. Strategies Towards Improving the Stability of All-Inorganic Perovskite Quantum Dots

Abstract
Perovskite quantum dots (PQDs) have attracted significant interests in the past few years because of their unique optical properties. Both all-inorganic and organic–inorganic perovskite quantum dots have shown great potential in optoelectronic devices such as light-emitting diodes (LEDs) for lighting and display technology. However, these commercial applications are severely impeded by their instability towards temperature, oxygen and moisture. Recently numerous strategies towards enhancing the stability of PQDs have been developed. This chapter reviews the strategies of improving the stability of all-inorganic perovskite quantum dots in detail, which are classified into two directions: (i) compositional adjustment and (ii) surface engineering.
Kai Gu, Mu Yang, Hongshang Peng

Backmatter

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