Hybrid organic/inorganic perovskites (e.g., CH3NH3PbI3) as light absorbers are promising players in the field of third-generation photovoltaics. Here we demonstrate a low-temperature vapor-assisted solution process to construct polycrystalline perovskite thin films with full surface coverage, small surface roughness, and grain size up to microscale. Solar cells based on the as-prepared films achieve high power conversion efficiency of 12.1%, so far the highest efficiency based on CH3NH3PbI3 with the planar heterojunction configuration. This method provides a simple approach to perovskite film preparation and paves the way for high reproducibility of films and devices. The underlying kinetic and thermodynamic parameters regarding the perovskite film growth are discussed as well.

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Planar Heterojunction Perovskite Solar Cells via Vapor-Assisted Solution Process

Increasing demand for raw materials means that alternatives to indium-tin oxide are desired for optically transparent electrode applications. Carbon nanotube, metal nanowire networks and regular metal grids have been investigated as possible options. In this review, these materials and recently rediscovered graphene are compared with the usual transparent conductive oxides.

Past achievements and future challenges in the development of optically transparent electrodes

1. Introduction and overview 2. Film stress and substrate curvature 3. Stress in anisotropic and patterned films 4. Delamination and fracture 5. Film buckling, bulging and peeling 6. Dislocation formation in epitaxial systems 7. Dislocation interactions and strain relaxation 8. Equilibrium and stability of surfaces 9. The role of stress in mass transport.

Thin Film Materials: Stress, Defect Formation and Surface Evolution

▪ Abstract Semiconductor nanowires and nanotubes exhibit novel electronic and optical properties owing to their unique structural one-dimensionality and possible quantum confinement effects in two dimensions. With a broad selection of compositions and band structures, these one-dimensional semiconductor nanostructures are considered to be the critical components in a wide range of potential nanoscale device applications. To fully exploit these one-dimensional nanostructures, current research has focused on rational synthetic control of one-dimensional nanoscale building blocks, novel properties characterization and device fabrication based on nanowire building blocks, and integration of nanowire elements into complex functional architectures. Significant progress has been made in a few short years. This review highlights the recent advances in the field, using work from this laboratory for illustration. The understanding of general nanocrystal growth mechanisms serves as the foundation for the rational sy...

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Semiconductor nanowires and nanotubes

The III-nitrides include the semiconductors AlN, GaN and InN, which have band gaps spanning the entire UV and visible ranges. Thin films of III-nitrides are used to make UV, violet, blue and green light-emitting diodes and lasers, as well as solar cells, high-electron mobility transistors (HEMTs) and other devices. However, the film growth process gives rise to unusually high strain and high defect densities, which can affect the device performance. X-ray diffraction is a popular, non-destructive technique used to characterize films and device structures, allowing improvements in device efficiencies to be made. It provides information on crystalline lattice parameters (from which strain and composition are determined), misorientation (from which defect types and densities may be deduced), crystallite size and microstrain, wafer bowing, residual stress, alloy ordering, phase separation (if present) along with film thicknesses and superlattice (quantum well) thicknesses, compositions and non-uniformities. These topics are reviewed, along with the basic principles of x-ray diffraction of thin films and areas of special current interest, such as analysis of non-polar, semipolar and cubic III-nitrides. A summary of useful values needed in calculations, including elastic constants and lattice parameters, is also given. Such topics are also likely to be relevant to other highly lattice-mismatched wurtzite-structure materials such as heteroepitaxial ZnO and ZnSe.

https://iopscience.iop.org/article/10.1088/0034-4885/72/3/036502/pdf

X-ray diffraction of III-nitrides

A Review of Materials Science. Vacuum Science and Technology. Physical Vapor Deposition. Chemical Vapor Deposition. Film Formation and Structure. Characterization of Thin Films. Epitaxy. Interdiffusion and Reactions in Thin Films. Mechanical Properties of Thin Films. Electrical and Magnetic Properties of Thin Films. Optical Properties of Thin Films. Metallurgical and Protective Coatings. Modification of Surfaces and Films. Emerging Thin-Film Materials and Applications. Appendixes. Index.

The Materials Science of Thin Films

Foreword to First Edition Preface Acknowledgments A Historical Perspective Chapter 1 A Review of Materials Science 1.1. Introduction 1.2. Structure 1.3. Defects in Solids 1.4. Bonds and Bands in Materials 1.5. Thermodynamics of Materials 1.6. Kinetics 1.7. Nucleation 1.8. An Introduction to Mechanical Behavior 1.9. Conclusion Exercises References Chapter 2 Vacuum Science and Technology 2.1. Introduction 2.2. Kinetic Theory of Gases 2.3. Gas Transport and Pumping 2.4. Vacuum Pumps 2.5. Vacuum Systems 2.6. Conclusion Exercises References Chapter 3 Thin-Film Evaporation Processes 3.1. Introduction 3.2. The Physics and Chemistry of Evaporation 3.3. Film Thickness Uniformity and Purity 3.4. Evaporation Hardware 3.5. Evaporation Processes and Applications 3.6. Conclusion Exercises References Chapter 4 Discharges, Plasmas, and Ion-Surface Interactions 4.1. Introduction 4.2. Plasmas, Discharges, and Arcs 4.3. Fundamentals of Plasma Physics 4.4. Reactions in Plasmas 4.5. Physics of Sputtering 4.6. Ion Bombardment Modification of Growing Films 4.7. Conclusion Exercises References Chapter 5 Plasma and Ion Beam Processing of Thin Films 5.1. Introduction 5.2. DC, AC, and Reactive Sputtering Processes 5.3. Magnetron Sputtering 5.4. Plasma Etching 5.5. Hybrid and Modified PVD Processes 5.6. Conclusion Exercises References Chapter 6 Chemical Vapor Deposition 6.1. Introduction 6.2. Reaction Types 6.3. Thermodynamics of CVD 6.4. Gas Transport 6.5. Film Growth Kinetics 6.6. Thermal CVD Processes 6.7. Plasma-Enhanced CVD Processes 6.8. Some CVD Materials Issues 6.9. Safety 6.10. Conclusion Exercises References Chapter 7 Substrate Surfaces and Thin-Film Nucleation 7.1. Introduction 7.2. An Atomic View of Substrate Surfaces 7.3. Thermodynamic Aspects of Nucleation 7.4. Kinetic Processes in Nucleation and Growth 7.5. Experimental Studies of Nucleation and Growth 7.6. Conclusion Exercises References Chapter 8 Epitaxy 8.1. Introduction 8.2. Manifestations of Epitaxy 8.3. Lattice Misfit and Defects in Epitaxial Films 8.4. Epitaxy of Compound Semiconductors 8.5. High-Temperature Methods for Depositing Epitaxial Semiconductor Films 8.6. Low-Temperature Methods for Depositing Epitaxial Semiconductor Films 8.7. Mechanisms and Characterization of Epitaxial Film Growth 8.8. Conclusion Exercises References Chapter 9 Film Structure 9.1. Introduction 9.2. Structural Morphology of Deposited Films and Coatings 9.3. Computational Simulations of Film Structure 9.4. Grain Growth, Texture, and Microstructure Control in Thin Films 9.5. Constrained Film Structures 9.6. Amorphous Thin Films 9.7. Conclusion Exercises References Chapter 10 Characterization of Thin Films and Surfaces 10.1. Introduction 10.2. Film Thickness 10.3. Structural Characterization of Films and Surfaces 10.4. Chemical Characterization of Surfaces and Films 10.5. Conclusion Exercises References Chapter 11 Interdiffusion, Reactions, and Transformations in Thin Films 11.1. Introduction 11.2. Fundamentals of Diffusion 11.3. Interdiffusion in Thin Metal Films 11.4. Compound Formation and Phase Transformations in Thin Films 11.5. Metal-Semiconductor Reactions 11.6. Mass Transport in Thin Films under Large Driving Forces 11.7. Conclusion Exercises References Chapter 12 Mechanical Properties of Thin Films 12.1. Introduction 12.2. Mechanical Testing and Strength of Thin Films 12.3. Analysis of Internal Stress 12.4. Techniques for Measuring Internal Stress in Films 12.5. Internal Stresses in Thin Films and Their Causes 12.6. Mechanical Relaxation Effects in Stressed Films 12.7. Adhesion 12.8. Conclusion Exercises References Index

Milton Ohring

Papers

The Materials Science of Thin Films

Materials science of thin films : deposition and structure

Chapter 1 – A Review of Materials Science

Chapter 7 – Substrate Surfaces and Thin-Film Nucleation

Chapter 9 – Film Structure