Development of Functional Materials as White-LED Phosphors to Improve Color Rendering in Display Devices

Abstract

Phosphor materials are critical components in various display technologies. These materials play a significant role in converting the energy from electrons or photons into visible light. While traditional phosphors have served well in many applications, there are several reasons why there is a continuous drive to develop new phosphor materials. The current research is driven by the need for displays that offer improved performance, expanded color gamut, thermal stability, durability, and cost-effectiveness. Narrow-band emitting phosphors improve lighting, displays, scientific research, and medical technology performance, energy efficiency, and quality by properly tuning the visible wavelengths. A few red-emitting phosphors fulfil the required standards of ideal white light emission from LED. The blue light excitable red emitting phosphor materials are essential components in display devices, contributing to color balance, expanded color gamut, energy efficiency, display performance, and application flexibility. The current research is focussed on this area for advancing display technology and meeting the evolving needs of consumers and industries. w-LEDs with narrow emission bandwidths and higher UV or blue LED chip efficiency are the primary goals of the current thesis work. This research augments the development of suitable red-emitting phosphors for white LED. The hierarchy of work done is represented as follows: • Reviewing the literature on rare earth activation and different host materials. • Studying the facile synthesis routes for tailor-made phosphors. • Studying red-emitting phosphor’s structure, morphology, composition, and luminosity. • Developing enhanced red-emitting phosphors for use in displays, LEDs, and medicine. The work has been divided into seven chapters: an introduction with a literature review, experimental and characterization techniques, results, and a discussion of the three Eu3+-doped host types Ca2La2O5, SrZr2La2O7, and SrZr2CaLa2O8 and their specific properties. Finally, a summary and future work. Chapter 1 briefly discusses the phenomena of photoluminescence and luminescence. This study analyzed host and dopant materials used in luminescence applications for optical and morphological properties. A comprehensive literature review on red-emitting phosphors was done. Chapter 2 describes tests, methodologies, and optimization of the selected materials' synthesis. Briefly discuss criterion assessment and analytical methods and technologies used in the thesis. Chapter 3 describes the photoluminescence and synthesis of Ca2La2O5:Eu3+, a new red-light phosphor. Stokes-shifted red photoluminescence was seen in Ca2La2O5:Eu3+ (x = 0.5-2.5 mol%) phosphor samples. Photoluminescence (PL) at 627 nm, was brighter than Eu3+ ion emission at 615 nm, showing exceptional colour purity in the novel red-emitting phosphors. A narrow-band, red-emitting multilayer phosphor is examined in Chapter 4. Phosphor emits red after 279 nm excitation. Emission wavelengths are 395–627 nm, while self-excitation wavelengths are 395, 467, and 590 nm. The cascade excitation spectrum starts at 279 nm and continues at 395, 467, and 590 nm. Photon emission, absorption, and emissions illustrate the increased luminescence efficiency and smaller FWHM of 8.6 nm at 627 nm. Chapter 5 describes the production and brightness of SrZr2CaLa2O8:Eu3+, a new direct white light-emitting phosphor. For color-tunability and purity, this chapter examines the rare single phase phosphor, SrZr2CaLa2O8:Eu3+ emitting red to white light and responding to UV rays. Ca2La2O5:Eu3+ (x=0.5 to 2.5 mol%), a tunable-color phosphor, was developed via a modified solid-state reaction with a chemical flux due to its 250–600 nm absorption spectrum. Color coordinates (x, y) for the white (0.41, 0.35) and red (0.62, 0.38) spectra were determined at excitable wavelengths of 395 and 467 nm. Chapter 7 reviews the study, makes conclusions, and suggests additional research.