ISBN: 3-540-66699-0
TITLE: Photoelectric Properties and Applications of Low-Mobility Semiconductors
AUTHOR: Knenkamp, Rolf
TOC:

1. Introduction 1
1.1 Purpose of This Book 2
1.2 Basic Material Characterization and Preparation 2
1.2.1 Hydrogenated Amorphous Silicon 2
1.2.2 Nano-Crystalline Films 5
1.2.3 Fullerenes 8
2. Basic Concepts of Low-Mobility Transport 11
2.1 Localization 11
2.2 Definition of Transport Parameters 14
2.3 Experiments to Probe the Carrier Transport 16
3. Transport in a-Si:H and Its Alloys 21
3.1 Basic Experimental Results 21
3.2 Time-Resolved Photoconductance 22
3.2.1 Trapping in Shallow Band-tail States 23
3.2.2 Drift Mobility 24
3.2.3 Electric Field Profiles 26
3.2.4 Transition From Shallow to Deep States 27
3.2.5 Trapping in Deep States 28
3.2.6 Correlation Between Shallow and Deep States 29
3.3 Unipolar Devices 30
3.3.1 Light-Activated Charge Storage Device 30
3.3.2 Thin-Film-Transistor (TFT) 30
3.4 Recombination-Limited Transport 32
3.4.1 Undoped a-Si:H 33
3.4.2 Doped and Alloyed Films 33
3.4.3 Structural Relaxation Effects 35
3.5 Bipolar Transport: a-Si:H Solar Cells 36
3.6 Summary 39
4. Transport in Porous TiO_2 and TiO_2-Based Devices 41
4.1 Basic Characterization of Porous TiO_2 41
4.1.1 Structural Characterization 41
4.1.2 Doping 41
4.1.3 Quantum Confinement 44
4.2 Photoelectric Properties 45
4.3 Solid-State Hetero-Junctions 52
4.3.1 Schottky Barrier Devices 52
4.3.2 Semiconductor Hetero-Junctions 52
4.3.3 Quantum Dot Hetero-Junctions 54
4.4 Devices 59
4.4.1 The Eta-Cell Concept 59
4.4.2 Material Selection and First Experimental Results 61
5. Transport in C_60 65
5.1 Basic Results 65
5.1.1 Dark Conductivity 65
5.1.2 Photocurrent Spectra 66
5.2 Intra-Molecular Excitation Scheme 67
5.2.1 Theoretical Background 67
5.2.2 Experimental Results for the 00-Transition 69
5.3 Intermolecular Charge Transport in C_60 Films 70
5.3.1 Quantum Generation Efficiency and Carrier Range 71
5.3.2 The Nature of Transport States in C_60 73
5.3.3 Mechanism of Charge Transport 75
5.3.4 Electron and Hole Drift Mobilities and Recombination Times 76
5.4 Effect of Oxygen 78
5.5 Discussion of Transport Results 81
5.6 The PolymerFullerene Solar Cell 82
6. Conclusions 83
References 87
Index 97
END
