Facile Physiochemical and Structural Modulation of Solution-Processed Inorganic Semiconductor Films for Broadband Photodetectors

Abstract

Photodetectors, with their myriad applications spanning across industries such as telecommunications, biomedical engineering, environmental monitoring, and security systems, have emerged as pivotal components in the advancement of modern technology. The essential function of photodetectors, which is to convert light into electrical signals, forms the cornerstone of a host of critical technologies and scientific explorations. As the world grapples with the challenges of the 21st century, including climate change, disease diagnosis, data communication, and national security, the role of photodetectors has become increasingly significant. This dissertation aims to delve deep into the realm of photodetectors handling wide range of electromagnetic wave, with an emphasis on the importance of semiconductor materials that contribute to their operation. This study is divided into two parts. The first part focuses on photo-assisted vacancy control in solution-processed inorganic semiconductor films, primarily discussing how ultraviolet (UV) radiation can mediate oxygen and atomic vacancies in semiconductors, thereby enhancing the sensitivity of photodetectors. The second part delves into the role of precursor modulation and scale-down integration, exploring the potential for enhancing the sensitivity of ionizing radiation detectors by modulating micro-scale particle size. Chapter 1 of the dissertation, "Introduction and Literature Reviews," provides a comprehensive overview of the field of photodetectors. The chapter begins with a detailed review of the existing literature, presenting a survey of photodetector classifications based on structural types. Next, the discussion proceeds to the integral element of photodetectors, which is the semiconductor material. After a thorough explanation of the different classifications of photodetectors and semiconductor materials depending on the light spectrum, the chapter deals with the deposition methods of inorganic semiconductors including vacuum-/vapor-based and solution-based deposition methods. Furthermore, an exploration of functional modulation of solution-processed inorganic semiconductors is described, which focus on how the strategies such as vacancy engineering and molecular design of precursor solutions can aid in improving the performance of photodetectors. These fundamental concepts set the stage for the advanced research presented in the subsequent chapters of the dissertation. Chapter 2, "Photo-mediated Oxygen Vacancy Promotion in Preferentially Grown Oxide Semiconductors for Ultraviolet Photodetectors," examines the use of DUV radiation to promote oxygen vacancies in texturally grown oxide semiconductors. Oxygen vacancies are a form of defects that can exist in the lattice structure of semiconductors. By using UV radiation to enhance these vacancies, it is possible to improve the optical and electrical properties of semiconductors, leading to better-performing photodetectors. Chapter 3, "UV-mediated Atomic Vacancies Promotion in Two-dimensional Multilayers for Enhanced Sensitivity of Broadband Photodetectors," extends the research into UV-mediated vacancy promotion to the realm of two-dimensional (2D) multilayer structures. 2D materials offer a plethora of unique properties that make them attractive for photodetector applications, such as high optical absorption and a large surface-to-volume ratio. By leveraging UV radiation to promote atomic vacancies in these materials, we can further enhance the sensitivity of photodetectors across a broad spectrum. The second part of the dissertation begins with Chapter 4, "Studies on Enhanced Sensitivity and Scale Down of Ionizing Radiation Detectors by Modulating Micro-Scale Particle Size." It dives into the exploration of precursor modulation and the role of scale-down integration in photodetectors. Here, we particularly focus on ionizing radiation detectors. The particle size of solution-processed semiconductors, particularly particle-in-binder method, directly affects their optical and electrical properties, consequently influencing the performance of photodetectors. Hence, by controlling and modulating the particle size at the micro-scale, we can enhance the sensitivity of these detectors. This chapter takes a closer look at these size-dependent phenomena and their implications on the functionality and performance of ionizing radiation detectors.