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Author: Heyong Wang
Publisher: Linköping University Electronic Press
ISBN: 9179298133
Category : Electronic books
Languages : en
Pages : 61
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Book Description
Metal halide perovskites have attracted significant attention for light-emitting applications, because of their excellent properties, such as high photoluminescence quantum yields (PLQYs), good charge mobility, narrow emission bandwidth, readily tunable emission spectra ranging from ultraviolet to near-infrared, and solution processability. Since the first room-temperature perovskite-based light-emitting diodes (PeLEDs) reported in 2014, tremendous efforts have been made to promote the efficiencies of PeLEDs, including theoretical simulation, materials design, and device engineering. To reach the ultimate goal of commercialization, PeLEDs with both high-efficiency and long-term operational stability are desired. Achieving high-quality perovskite emissive films is key towards this goal. Centering around the high-quality perovskite films, in this thesis, we demonstrate effective synthesis strategies for the deposition of high-quality perovskite films (including both three-dimensional and mixed-dimensional perovskites) and investigate the effects of ion migration in the perovskite films on the performance of PeLEDs. Due to the fast crystallization nature of perovskites and the low formation energy of defects, controlling the crystallization processes of these films has proved to be an effective approach for achieving high-quality perovskite films. For three-dimensional (3D) perovskite films, we have controlled the formation of these films through the assistance of molecules with the amino group. Herein, we have chosen an electron-transport molecule with two amino groups, 4,4’-diaminodiphenyl sulfone (DDS), to control the crystallization process of perovskite films (Paper 1). The resulting perovskite films consists of in-situ formed high quality perovskite nanocrystals embedded in the electron-transport molecular matrix, resulting in improved PLQYs and structural stability. PeLEDs based on these perovskite films have exhibited both high efficiency and long operational stability. In addition, we have investigated the formation of mixed-dimensional perovskite films. Efficient PeLEDs based on mixed-dimensional perovskite films were fabricated with tin dioxide (SnO2) as an electron transport layer (Paper 3). We also note that the deposition methods have a significant impact on the morphology and optical properties of prepared mixed-dimensional perovskite films (Paper 4). In addition, we provide an effective method to extend the deposition of mixed-dimensional perovskite films, replacing organic ammonium halides with amines in the perovskite precursor solutions to form organic spacer cations through the in-situ protonation process of amines (Paper 2). In spite of these efforts, the performance of PeLEDs is still far from the commercialization standard, partially limited by ion migration. In Paper 5, we discuss impacts of mobile ions in the perovskite films on the performance of PeLEDs. We find that a dynamic redistribution of mobile ions can change current density of a device, leading to EQE/hysteresis during forward and reverse voltage scan and enhanced EQE under constant driving voltages. In addition, we have found that excess mobile ions in the perovskite layer can aggravate the hysteresis and shorten the operational stability of PeLEDs. In this thesis, we also discuss the remaining key challenges in the PeLED field, including the achievement of high-performance blue, white, and lead-free PeLEDs, as well as possible strategies to address these challenges. We hope that our research findings provide insights into the basic science behind the perovskite materials, and broadly benefit other optoelectronic communities, such as perovskite solar cells, flexible electronics, and so on. Metall-halid-perovskiter har fått mycket uppmärksamhet för deras möjlighet att användas i ljusemitterande applikationer på grund utav utmärkta egenskaper så som högt fotoluminiscent kvantutbyte (PLQYs), god mobilitet, smalt emissionsband, lättjusterat emissionsspektra i intervallet ultraviolett till nära infrarött, samt för att de kan beredas med en lösningsbaserad process. Ända sedan de första perovskitbaserade ljusdioderna (PeLEDs) som verkande i rumstemperatur rapporterades 2014 har enormt arbete lagts ner på att öka effektiviteten hos PeLEDs, till exempel genom teoretiska simuleringar, materialdesign och teknisk utformning utav lysdioden. För att nå det slutgiltiga målet med kommersialisering behövs PeLEDs som har både hög effektivitet och driftstabilitet. Att uppnå högkvalitativa emitterande perovskitfilmer är nyckeln för att nå detta mål. I den här avhandlingen, vilken fokuserar på högkvalitativa perovskitfilmer, demonstrerar vi effektiva syntetiseringsstrategier för deponering utav högkvalitativa perovskitfilmer och undersöker effekterna jonmigration har på prestandan i perovskitfilmerna i PeLEDs. På grund utav den snabbkristalliserande naturen hos perovskitfilmer och den låga bildningsenergin för defekter så har kontroll utav kristallisationsprocessen av dessa filmer visat sig vara en effektiv väg för att uppnå högkvalitativa perovskitfilmer. När det gäller tredimensionella perovskitfilmer så har vi kontrollerat bildandet av dessa filmer genom assistans från molekyler med aminogrupper. Vi har valt en elektrontransporterande molekyl som har två aminogrupper, 4,4’- diaminodifenyl sulfon (DDS), för att kontrollera kristallisationsprocessen av perovskitfilmer (artikel 1). De beredda perovskitfilmerna bestod av insitu- bildade högkvalitativa perovskitnanokristaller inbäddade i en elektrontransporterande molekylär matris vilket resulterade i förbättrat fotoluminiscent-kvantutbyte och strukturell stabilitet. PeLEDs baserade på dessa perovskitfilmer har uppvisat både hög effektivitet och lång driftstabilitet. Därtill har vi undersökt bildandet av blanddimensionella perovskiter. Effektiva PeLEDs baserade på blanddimensionella perovskiter var tillverkade med tenndioxid (SnO2) som elektrontransportlager (artikel 3). Vi noterade även att val av deponeringsmetod hade signifikant effekt på IV morfologi och optiska egenskaper av de beredda blanddimensionella perovskitfilmerna (artikel 4). Därutöver tillhandahöll vi en effektiv metod för att deponera blanddimensionella perovskitfilmer genom att ersätta de vanligen använda organiska ammoniumhaliderna med aminer i prekursorlösningen för att bilda organiska distansierande katjonfilmer genom en in-situ-protoneringsprocess av aminer (artikel 2). Även om PeLEDs med högkvalitativa perovskitfilmer har visat förbättrad effektivitet och driftstabilitet så uppvisar lysdioderna fortfarande egenskaper som associeras med jonmigration. I artikel 5 diskuterar vi effekten av mobila joner i perovskitfilmer och hur de påverkar PeLEDs prestanda. Vi fann att den dynamiska omfördelningen av mobila joner i perovskitskiktet kan ändra det elektriska nettofältet i perovskitskiktet, modifiera laddningsbärarnas rekombination i perovskitskiktet och leda till ostadig strömdensitet. Dessutom har vi funnit att överskott av mobila joner i perovskitskiktet är en av de största anledningarna till den korta driftstabiliteten för PeLEDs. I denna avhandling diskuterar vi även kvarstående nyckelproblem i PeLED-fältet så som bedriften att uppnå högpresterande blå, vita och blyfria PeLEDs så väl som möjliga strategier att möta dessa utmaningar. Våra forskningsresultat ger insikter om den grundläggande vetenskapen bakom perovskitmaterialen vilka vi tror kommer vara till stort gagn för andra optoelektroniska fält, så som perovskitsolceller, flexibel elektronik och så vidare.
Author: Heyong Wang
Publisher: Linköping University Electronic Press
ISBN: 9179298133
Category : Electronic books
Languages : en
Pages : 61
Get Book Here
Book Description
Metal halide perovskites have attracted significant attention for light-emitting applications, because of their excellent properties, such as high photoluminescence quantum yields (PLQYs), good charge mobility, narrow emission bandwidth, readily tunable emission spectra ranging from ultraviolet to near-infrared, and solution processability. Since the first room-temperature perovskite-based light-emitting diodes (PeLEDs) reported in 2014, tremendous efforts have been made to promote the efficiencies of PeLEDs, including theoretical simulation, materials design, and device engineering. To reach the ultimate goal of commercialization, PeLEDs with both high-efficiency and long-term operational stability are desired. Achieving high-quality perovskite emissive films is key towards this goal. Centering around the high-quality perovskite films, in this thesis, we demonstrate effective synthesis strategies for the deposition of high-quality perovskite films (including both three-dimensional and mixed-dimensional perovskites) and investigate the effects of ion migration in the perovskite films on the performance of PeLEDs. Due to the fast crystallization nature of perovskites and the low formation energy of defects, controlling the crystallization processes of these films has proved to be an effective approach for achieving high-quality perovskite films. For three-dimensional (3D) perovskite films, we have controlled the formation of these films through the assistance of molecules with the amino group. Herein, we have chosen an electron-transport molecule with two amino groups, 4,4’-diaminodiphenyl sulfone (DDS), to control the crystallization process of perovskite films (Paper 1). The resulting perovskite films consists of in-situ formed high quality perovskite nanocrystals embedded in the electron-transport molecular matrix, resulting in improved PLQYs and structural stability. PeLEDs based on these perovskite films have exhibited both high efficiency and long operational stability. In addition, we have investigated the formation of mixed-dimensional perovskite films. Efficient PeLEDs based on mixed-dimensional perovskite films were fabricated with tin dioxide (SnO2) as an electron transport layer (Paper 3). We also note that the deposition methods have a significant impact on the morphology and optical properties of prepared mixed-dimensional perovskite films (Paper 4). In addition, we provide an effective method to extend the deposition of mixed-dimensional perovskite films, replacing organic ammonium halides with amines in the perovskite precursor solutions to form organic spacer cations through the in-situ protonation process of amines (Paper 2). In spite of these efforts, the performance of PeLEDs is still far from the commercialization standard, partially limited by ion migration. In Paper 5, we discuss impacts of mobile ions in the perovskite films on the performance of PeLEDs. We find that a dynamic redistribution of mobile ions can change current density of a device, leading to EQE/hysteresis during forward and reverse voltage scan and enhanced EQE under constant driving voltages. In addition, we have found that excess mobile ions in the perovskite layer can aggravate the hysteresis and shorten the operational stability of PeLEDs. In this thesis, we also discuss the remaining key challenges in the PeLED field, including the achievement of high-performance blue, white, and lead-free PeLEDs, as well as possible strategies to address these challenges. We hope that our research findings provide insights into the basic science behind the perovskite materials, and broadly benefit other optoelectronic communities, such as perovskite solar cells, flexible electronics, and so on. Metall-halid-perovskiter har fått mycket uppmärksamhet för deras möjlighet att användas i ljusemitterande applikationer på grund utav utmärkta egenskaper så som högt fotoluminiscent kvantutbyte (PLQYs), god mobilitet, smalt emissionsband, lättjusterat emissionsspektra i intervallet ultraviolett till nära infrarött, samt för att de kan beredas med en lösningsbaserad process. Ända sedan de första perovskitbaserade ljusdioderna (PeLEDs) som verkande i rumstemperatur rapporterades 2014 har enormt arbete lagts ner på att öka effektiviteten hos PeLEDs, till exempel genom teoretiska simuleringar, materialdesign och teknisk utformning utav lysdioden. För att nå det slutgiltiga målet med kommersialisering behövs PeLEDs som har både hög effektivitet och driftstabilitet. Att uppnå högkvalitativa emitterande perovskitfilmer är nyckeln för att nå detta mål. I den här avhandlingen, vilken fokuserar på högkvalitativa perovskitfilmer, demonstrerar vi effektiva syntetiseringsstrategier för deponering utav högkvalitativa perovskitfilmer och undersöker effekterna jonmigration har på prestandan i perovskitfilmerna i PeLEDs. På grund utav den snabbkristalliserande naturen hos perovskitfilmer och den låga bildningsenergin för defekter så har kontroll utav kristallisationsprocessen av dessa filmer visat sig vara en effektiv väg för att uppnå högkvalitativa perovskitfilmer. När det gäller tredimensionella perovskitfilmer så har vi kontrollerat bildandet av dessa filmer genom assistans från molekyler med aminogrupper. Vi har valt en elektrontransporterande molekyl som har två aminogrupper, 4,4’- diaminodifenyl sulfon (DDS), för att kontrollera kristallisationsprocessen av perovskitfilmer (artikel 1). De beredda perovskitfilmerna bestod av insitu- bildade högkvalitativa perovskitnanokristaller inbäddade i en elektrontransporterande molekylär matris vilket resulterade i förbättrat fotoluminiscent-kvantutbyte och strukturell stabilitet. PeLEDs baserade på dessa perovskitfilmer har uppvisat både hög effektivitet och lång driftstabilitet. Därtill har vi undersökt bildandet av blanddimensionella perovskiter. Effektiva PeLEDs baserade på blanddimensionella perovskiter var tillverkade med tenndioxid (SnO2) som elektrontransportlager (artikel 3). Vi noterade även att val av deponeringsmetod hade signifikant effekt på IV morfologi och optiska egenskaper av de beredda blanddimensionella perovskitfilmerna (artikel 4). Därutöver tillhandahöll vi en effektiv metod för att deponera blanddimensionella perovskitfilmer genom att ersätta de vanligen använda organiska ammoniumhaliderna med aminer i prekursorlösningen för att bilda organiska distansierande katjonfilmer genom en in-situ-protoneringsprocess av aminer (artikel 2). Även om PeLEDs med högkvalitativa perovskitfilmer har visat förbättrad effektivitet och driftstabilitet så uppvisar lysdioderna fortfarande egenskaper som associeras med jonmigration. I artikel 5 diskuterar vi effekten av mobila joner i perovskitfilmer och hur de påverkar PeLEDs prestanda. Vi fann att den dynamiska omfördelningen av mobila joner i perovskitskiktet kan ändra det elektriska nettofältet i perovskitskiktet, modifiera laddningsbärarnas rekombination i perovskitskiktet och leda till ostadig strömdensitet. Dessutom har vi funnit att överskott av mobila joner i perovskitskiktet är en av de största anledningarna till den korta driftstabiliteten för PeLEDs. I denna avhandling diskuterar vi även kvarstående nyckelproblem i PeLED-fältet så som bedriften att uppnå högpresterande blå, vita och blyfria PeLEDs så väl som möjliga strategier att möta dessa utmaningar. Våra forskningsresultat ger insikter om den grundläggande vetenskapen bakom perovskitmaterialen vilka vi tror kommer vara till stort gagn för andra optoelektroniska fält, så som perovskitsolceller, flexibel elektronik och så vidare.
Author: Hongling Yu
Publisher: Linköping University Electronic Press
ISBN: 9179298095
Category : Electronic books
Languages : en
Pages : 72
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Book Description
Metal halide perovskites (MHPs) are recognized as promising semiconductor materials for a variety of optical and electrical device applications due to their cost-effective and outstanding optoelectronic properties. As one of the most significant applications, perovskite light-emitting diodes (PeLEDs) hold promise for future lighting and display technologies, attributed to their high photoluminescence quantum yield (PLQY), high color purity, and tunable emission color. The emission colors of PeLEDs can be tuned by mixing the halide anions, adjusting the size of perovskite nanocrystals, or changing the dimensionality of perovskites. However, in practice, all these different approaches have their own advantages and challenges. This thesis centres around the color tunability of perovskites, aiming to develop PeLEDs with different colors using different approaches. We first demonstrate red and near-infrared PeLEDs using a straightforward approach – in situ solution-processed perovskite quantum dots (PQDs). PQDs prepared from colloidal approaches are widely reported and used in LEDs. In contrast, PQDs prepared from the in situ approaches are hardly reported, although they have advantages for device applications. By employing aromatic ammonium iodide (1-naphthylmethyl ammonium iodide, NMAI) as an agent into perovskite precursor solutions, together with annealing temperature modulation, we obtain in situ grown PQDs delivering high external quantum efficiencies (EQEs) of up to 11.0% with tunable electroluminescence (EL) spectra (667 - 790 nm). Our in situ generated PQDs based on pure-halogen perovskites can be easily obtained through a simple deposition process and free of phase segregation, making them a more promising approach for tuning the emission colors of perovskite LEDs. We then move to blue PeLEDs using cesium-based mixed-Br/Cl perovskites. Although mixed halides are a straightforward strategy to tune the emission color, PeLEDs based on this approach suffer from poor color stability, which is attributed to surface defects at grain boundaries. Under the condition of optical excitations, light density over a certain value (a threshold), oxygen, and surface defects at perovskite grain boundaries are found to be key factors inducing photoluminescence (PL) spectral instability of CsPb(Br1?xClx)3 perovskites. Upon electrical bias, defects at grain boundaries provide undesirable halide migration channels, responsible for EL spectral instability issues. Through effective defect passivation, the PL spectral resistance to oxygen is enhanced; moreover, high-performance and color-stable blue PeLEDs are achieved, delivering a maximum luminance of 5351 cd m–2 and a peak EQE of 4.55% with a peak emission wavelength at 489 nm. These findings provide new insights into the color instability issue of mixed halide blue perovskites, against which we also demonstrate an effective strategy. We finally realize single-emissive-layer (EML) white PeLEDs by employing a mixed halide perovskite film as the EML. In spite of high-performance monochromatic blue, green, and red colors, the development of white PeLEDs, especially for single-EML ones, remains a very big challenge. By effective modulation of the halide salt precursors, we achieve single-EML white PeLEDs with Commission Internationale de L’Eclairage (CIE) coordinates of (0.33, 0.33), close to those (0.3128, 0.3290) of the CIE standard illuminant D65. This work not only provides a successful demonstration of a single-EML white PeLED, but also provides useful guidelines for the future development of highperformance single-EML white PeLEDs.
Author: Hong Meng
Publisher: John Wiley & Sons
ISBN: 3527353208
Category : Technology & Engineering
Languages : en
Pages : 373
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Book Description
Perovskite Light Emitting Diodes An introduction to revolutionary display technology Perovskite Light Emitting Diodes, commonly referred to as Pe-LEDs, leverage a perovskite nanocrystal core to engender a luminous and efficient diode, holding the potential to bring about a paradigm shift in the realm of display technology. In recent times, Pe-LEDs have garnered substantial industrial interest due to their intrinsic capability to exhibit a diverse array of colors with exceptional fidelity, their operation at low voltage thresholds, and their straightforward structural composition. The prospective implications for enabling cost-effective, heightened-performance flat-panel displays as well as flexible display solutions remain notably profound. Perovskite Light Emitting Diodes: Materials and Devices presents a comprehensive and insightful overview of these diodes and their multifaceted applications. Commencing with an incisive exploration of the historical trajectory of this technology, alongside a delineation of its foundational materials and intricate device architectures, this compendium provides a gateway into both contemporaneous state-of-the-art deployments and the vanguard of ongoing research endeavors directed towards charting future advancements. Perovskite Light Emitting Diodes readers will also find: Stability analysis for different Pe-LED devices, a key aspect of creating physical displays Authorship by an established expert in organic electronics Detailed discussion of perovskite preparation methods including ultrasonic, solvent heat, thermal injection, and many more Perovskite Light Emitting Diodes is ideal for materials scientists, electrical engineers, solid state chemists, solid state physicists, inorganic chemists, and any researchers or engineers working with display technology.
Author: Michael Debebe Worku
Publisher:
ISBN:
Category : Materials science
Languages : en
Pages : 0
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Book Description
Metal halide perovskites have received significant attention in the past decade as a promising class of material for energy harvesting, light emission and detection as well as various other solid-state devices. The easy solution processability, high defect tolerance, abundance of raw materials and exceptional optoelectronic properties have warranted intense investigation into their fundamental material physics and their device integration. Particularly, metal halide perovskite light-emitting diodes (LEDs) are thought to hold promise for next generation displays due to their narrow and tunable emission, high radiative efficiency and easy processability. For instance, red and green perovskite LEDs have now achieved the high external quantum efficiency required for commercial applications, on par with more mature lighting technologies such as organic LEDs and quantum dot LEDs. However, there are still several roadblocks that need to be overcome before perovskite LEDs can be considered a commercially viable technology. These challenges include, device stability, material toxicity, mass-production and development of efficient blue LEDs. The development of efficient blue LEDs is a major milestone in any display technology as it allows the production of multi-color images by combining the three primary colors red, green and blue (RGB). Similarly, the development of efficient white LEDs with excellent white light quality displaying high color rendering indices is also as important for solid-state lighting applications. In this dissertation, we explore two major themes related to the use of perovskites and perovskite related metal halide hybrids in light-emitting applications. The first and the broader work involves the study of various strategies to enable the realization of efficient blue perovskite LEDs. Three of the main challenges in obtaining efficient blue perovskite LEDs have been identified as band gap and emission tuning, poor radiative efficiency of perovskite blue emitters and charge carrier imbalance that results in suboptimal device performance. These issues are addressed in the first theme of this dissertation by introducing effective band gap and emission tuning strategies, improving radiative efficiency of blue perovskite emitters through trap passivation and engineering the energy band edges of perovskite thin films to obtain favorable band alignment and enhanced charge balance. In this theme, two methods are presented in chapter 2 and 3 to achieve band gap and emission control while ensuring spectral stability. These include the synthesis of perovskite hollow nanocrystals and phase control of perovskite multiple quantum well thin films. Perovskite hollow nanocrystals are shown to enable band gap and emission tuning through the formation of a hollow 3D crystal structure and quantum confinement. Reduced grain boundaries and passivation of surface trap sites in these nanocrystalline thin films are also shown to result in high radiative efficiencies. Although the formation of perovskite quantum wells has been shown to be an effective strategy to control the band gap and emission, the crystallization of multiple quantum well phases during thin film formation and fast energy funneling across phases has limited the application of perovskite quantum wells in color tunable and blue LEDs. In chapter 3, we show the addition of diammonium salts enables phase control in perovskite multiple quantum well thin films, resulting in color tunable emission. The presence of diammonium salts was also found to increase radiative efficiency enabling the fabrication of pure blue perovskite LEDs with good efficiency. Finally, energy band edge control of quasi-2D perovskites is also presented as a viable solution to charge injection barriers that appear due to unfavorable band alignment in blue perovskite LEDs. By modifying the dipole moment of organic spacer cations in quasi-2D perovskites through the addition of electron donating or withdrawing substituent groups, rational band edge control is achieved which enables improved blue LED performance due to enhanced charge balance. In the second theme of this dissertation, the use of low-dimensional metal halide hybrids in broadband white LEDs for high color quality applications is shown. The broadband emission spectra of low-dimensional metal halide hybrids are shown to be ideal for white light applications that require full spectrum coverage and high color rendering. The dissertation concludes by presenting a few exciting routes that could be explored to further improve the performance of blue and white LEDs based on perovskites and perovskite related materials. The work presented in this dissertation contributes to the field of perovskite LEDs by exploring the structure-processing-property-performance phase space and providing alternative routes to obtain spectrally stable and efficient blue perovskite LEDs as well as excellent light quality white LEDs, which could help transition perovskite LEDs to commercial viability.
Author: Nam-Gyu Park
Publisher: CRC Press
ISBN: 1000562328
Category : Science
Languages : en
Pages : 238
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Book Description
Perovskite is a well-known structure with the chemical formula ABX3, where A and B are cations coordinated with 12 and 6 anions, respectively, and X is an anion. When a halogen anion is used, the monovalent A and divalent B cations can be stabilized with respect to a tolerance factor ranging from ~0.8 to 1. Since the first report on ~10% efficiency and long-term stability of solid-state perovskite solar cells (PSCs) in 2012 and two subsequent seed reports on perovskite-sensitized solar cells in 2009 and 2011, PSCs have received increasing attention. The power conversion efficiency of PSCs was certified to be more than 25% in 2020, surpassing thin-film solar cell technologies. Methylammonium or formamidinium organic ion–based lead iodide perovskite has been used for high-efficiency PSCs. The first report on solid-state PSCs triggered perovskite photovoltaics, leading to more than 23,000 publications as of October 2021. In addition, halide perovskite has shown excellent performance when applied to light-emitting diodes (LEDs), photodetectors, and resistive memory, indicating that halide perovskite is multifunctional. This book explains the electro-optical and ferroelectric properties of perovskite and details the recent progress in scalable and tandem PSCs as well as perovskite LEDs and resistive memory. It is a useful textbook and self-help study guide for advanced undergraduate- and graduate-level students of materials science and engineering, chemistry, chemical engineering, and nanotechnology; for researchers in photovoltaics, LEDs, resistive memory, and perovskite-related opto-electronics; and for general readers who wish to gain knowledge about halide perovskite.
Author: Masoud Alahbakhshi
Publisher:
ISBN:
Category : Electrical engineering
Languages : en
Pages : 0
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Book Description
Metal halide perovskites, as a new type of hybrid semiconductors, have demonstrated promising optoelectronic properties for state-of-the-art and emerging photonic technologies such as pure color light-emitting diodes, cost-effective nano-lasers, and efficient photovoltaic devices. Owing to highly tunable emission wavelengths, high absorption coefficient, high exciton binding energy, narrow emission linewidth, and less expensive fabrication methods, perovskite materials are excellent choices for the next generation of optoelectronic applications. In this dissertation, we mainly focus on introducing and understanding the physics and processing of the perovskite lightemitting devices regarding their dynamic behavior associated with ionic doping and nanopatterning effects in perovskite materials. We begin by investigating a novel and facile approach to overcome some important limitations of Perovskite Light-Emitting Electrochemical Cells (PeLECs) such as intrinsic ion motion degradation, low brightness, and short operational lifetime. In this method, we leverage the advantages of new nanocomposite with an electrolyte polymer along with a lithium salt additive (LiPF6) incorporated into the CsPbBr3 perovskite structure in order to passivate and suppress the traps, defects, and pin-holes in perovskite thin films aiming to improve the morphology and achieve high-performance single layer PeLEC for green emission. By implementing the material characterization techniques, we scrutinize the optimization process for lithium salt additive and demonstrate the advantages of LiPF6 additive including high photoluminescence quantum yield (PLQY), and stable photoluminescence (PL) dynamics, electroluminescence (EL) stability, low hysteresis, and high efficiency of devices. Inspired by the successes of ionic additives in these types of PeLECs, we further investigate the operational stability of devices and reach 100 hours of operational lifetime which is a 5.6-fold improvement over devices with no LiPF6 additive. We further develop our research by utilizing a new synthesized ionic iridium complex to build a HostGuest system in PeLEC structure in order to effectively tune the color emission, improve the morphology and consequently increase the efficiency of PeLECs for future display applications. In the next part of this dissertation, we provide a unique method to construct a multilayer blue Perovskite Light-Emitting Diode (PeLED) by utilizing the electron and hole transport layers as well as Quasi-2D perovskite composition. We successfully show that implementing two long and small ligands into the 3D perovskite precursor can beneficially form both small and large n phases perovskite layers, for the selective energy transfer process, and eventually provide an extremely efficient blue PeLED device. The maximum 10% EQE, maximum luminance 5500 cd m-2 , and 170 min half lifetime (T50) operational stability have been demonstrated. In the last section, we present the novel nanoimprint lithography method in order to perform direct nanopatterning on halide perovskite thin films to create laser cavities. With a meticulous approach that includes a practical encapsulation method, we have exhibited the first demonstration of quasi-CW lasing from directly patterned perovskites with a high-quality cavity design.
Author: Chen Zou
Publisher:
ISBN:
Category :
Languages : en
Pages : 155
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Book Description
Metal halide perovskites were first rediscovered for photovoltaic applications in 2009. The performance of perovskite solar cells has undergone a rapid advancement with power conversion efficiency (PCE) increasing from 3.8% to over 25%, comparable to state-of-art commercial solar cells. Recent findings on excellent optoelectronic properties of perovskites like high photoluminescence quantum yield (PLQY), good charge transport and bandgap tunability motivate researchers to explore their applications in light-emitting devices such as light-emitting diodes (LEDs), multicolor displays and laser diodes. In this dissertation, I first introduce the development of perovskite LEDs (PeLEDs) and analyze key factors affecting the external quantum efficiency (EQE). The high refractive index of perovskites limits the light outcoupling efficiency to 20-25%. The next step to further increase EQEs should be focused on enhancing light extraction. Through an optical simulation, I found the emitter dipole orientation plays an important role. This finding may provide guidance on further performance boost of PeLEDs. CsPbI3 is the lowest bandgap all-inorganic perovskite, targeted for covering the red corner of CIE chromaticity diagram. However, CsPbI3 bulk films transition to undesirable orthorhombic phase at room temperature. CsPbI3 QDs are much more phase stable due to the reduced surface energy. Based on CsPbI3 QDs, I demonstrate a stable red-emission PeLED. To push perovskite materials towards commercialized display applications, I developed a high-resolution photolithographic approach to pattern multicolor perovskite thin films. This approach is based on a dry lift-off process, addressing the incompatibility of perovskites to common polar solvents. Using this approach, we fabricated a multicolor pixel array for liquid crystal displays (LCDs) and a prototype perovskite mirco-LED display. Besides great potential in display applications, perovskites have renewed people’s hope for achieving the long-standing goal of solution-processable electrically pumped laser diodes. I first demonstrate perovskite lasers integrated with distributed Bragg (DBR) and distributed feedback (DFB) cavities under optical pumping. Towards electrically pumped laser diodes, I suppressed the efficiency roll-off (droop) of perovskite LEDs by applying combined strategies. Finally, devices could be operated at high current densities up to 1 kA/cm2. Future work will be integrating DFB cavities with perovskite LEDs to approach the ultimate goal.
Author: Ye Zhou
Publisher: Springer Nature
ISBN: 9811566372
Category : Technology & Engineering
Languages : en
Pages : 374
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Book Description
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.
Author: Caleb Clifford Boyd
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
Organic-inorganic metal halide perovskites are a class of semiconductor materials with excellent optoelectronic properties that hold promise for applications including photovoltaics, light-emitting diodes, and detectors. They are fabricated from low-cost, scalable solution processing or vapor deposition methods and have readily tunable optoelectronic properties through manipulation of chemical composition. This unique combination of materials properties has opened the door for low-cost tandem photovoltaics, in which a wide band gap perovskite solar cell is paired with a low band gap solar cell such as silicon, copper indium gallium diselenide, or low band gap perovskites, reducing thermalization losses that are intrinsic to single junction solar cells and enabling higher power conversion efficiencies. However, to enable commercialization of this new technology, the stability of metal halide perovskites must be improved. In this dissertation, I first describe the current understanding of degradation mechanisms for metal halide perovskite solar cells and methods to prevent them. I then discuss in detail metal oxide barrier layer design to prevent oxygen and moisture ingress and reactions between halogen species from the perovskite film and metal contacts and use these barrier layers to demonstrate efficient devices that have state-of-the-art operational and thermal stabilities. I then apply these learnings to highly efficient perovskite/silicon tandems, enabled by a stable device architecture and a novel, triple-halide (I, Br, Cl) perovskite with excellent photostability and optoelectronic properties enabled by the addition of chlorine into the lattice. I conclude with an in-depth study of interfacial reactions between the perovskite and nickel oxide, a highly desirable hole transport layer for efficient and stable perovskite tandem solar cells and demonstrate a method to prevent these reactions, improving device voltages and efficiencies.
Author: Tsutomu Miyasaka
Publisher: John Wiley & Sons
ISBN: 3527347488
Category : Technology & Engineering
Languages : en
Pages : 484
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Book Description
Perovskite Photovoltaics and Optoelectronics Discover a one-of-a-kind treatment of perovskite photovoltaics In less than a decade, the photovoltaics of organic-inorganic halide perovskite materials has surpassed the efficiency of semiconductor compounds like CdTe and CIGS in solar cells. In Perovskite Photovoltaics and Optoelectronics: From Fundamentals to Advanced Applications, distinguished engineer Dr. Tsutomu Miyasaka delivers a comprehensive exploration of foundational and advanced topics regarding halide perovskites. It summarizes the latest information and discussion in the field, from fundamental theory and materials to critical device applications. With contributions by top scientists working in the perovskite community, the accomplished editor has compiled a resource of central importance for researchers working on perovskite related materials and devices. This edited volume includes coverage of new materials and their commercial and market potential in areas like perovskite solar cells, perovskite light-emitting diodes (LEDs), and perovskite-based photodetectors. It also includes: A thorough introduction to halide perovskite materials, their synthesis, and dimension control Comprehensive explorations of the photovoltaics of halide perovskites and their historical background Practical discussions of solid-state photophysics and carrier transfer mechanisms in halide perovskite semiconductors In-depth examinations of multi-cation anion-based high efficiency perovskite solar cells Perfect for materials scientists, crystallization physicists, surface chemists, and solid-state physicists, Perovskite Photovoltaics and Optoelectronics: From Fundamentals to Advanced Applications is also an indispensable resource for solid state chemists and device/electronics engineers.
