Effects of Device Structure and Operating Conditions on the Performance of Organometal Trihalide Perovskite Solar Cells : Device Characterization and Impedance Spectroscopy Study
Effects of Device Structure and Operating Conditions on the Performance of Organometal Trihalide Perovskite Solar Cells
- 주제(키워드) Perovskite solar cells , Electrochemical Impedance Spectroscopy , SCAPS simulations
- 발행기관 아주대학교
- 지도교수 Soonil Lee
- 발행년도 2017
- 학위수여년월 2017. 8
- 학위명 박사
- 학과 및 전공 일반대학원 에너지시스템학과
- 실제URI http://www.dcollection.net/handler/ajou/000000026006
- 본문언어 영어
- 저작권 아주대학교 논문은 저작권에 의해 보호받습니다.
초록/요약
In recent years, organometal trihalide perovskite (OTP) has been being an emerging material for application in high-efficiency solar cells. OTP-based solar cells have a lot of advantages including low cost, solution-processible availability. Despite high efficiency, the existence of defects in the bulk OTP materials and at the interface between them and other charge-transport materials is a hindering factor that deteriorates the performance of OTP photovoltaic devices. The effort of understanding the origin of those defects and their effects on the performance of OTP devices is the main goal of our work. In this work, we studied and investigated the effect of several trap states existing within CH3NH3PbI3-based planar solar cells (PSCs) with copper-doped nickel oxide (Cu:NiOx) as hole-extraction layers (HELs). Experimental current-voltage (J-V) characteristics and Electrochemical Impedance Spectroscopy (EIS) spectra were guidelines for us to detect the existence of defect in the bulk CH3NH3PbI3 (MAPbI3) active layer (AL) and at the interface between ALs and HELs. Based on those experimental evidences and real device structure, we built a model and utilized Solar Cell Capacitance Simulator (SCAPS) to simulate J-V curves and capacitance-conductance-frequency (C-G-f) spectra simultaneously. We were able to find some important parameters of the microscopic model, especially those belong to defects, including their energy level, energetic distribution, density and charge trapping probability. In addition, the microscopic models of the defect were able to efficiently describe the hysteresis phenomenon, that exhibits in variations of device performance with scan rate and direction. The systematic approach we reported in this work is general enough to be applied to other solar cell systems to identify and quantify defects hampering device operation. Detailed identification and quantification of defects are prerequisites for developing efficient passivation technique that can minimize detrimental defect effects to improve device performance further.
more목차
Chapter 1: Introduction 1
1.1. Thesis Overview 1
1.2. Introduction to organometal trihalide perovskite (OTP) materials 3
1.2.1. Crystal structures 3
1.2.2. Band-gap structure and electronic properties 7
1.2.3. Recombination dynamics 9
1.2.4. Dielectric properties 11
1.3. Electronic properties of NiOx and copper-doped NiOx 12
Chapter 2: Experimental procedures 14
2.1. Materials 14
2.2. Thin film and device fabrication 15
2.3. Material and device characterization 16
2.4. Device structure 18
2.5. Experimental results 19
Chapter 3: Optical and electrical simulations 21
3.1. Optical simulations 21
3.2. SCAPS simulation model 22
Chapter 4: Hole-extraction layer dependence of defect formation and operation of MAPbI3 planar solar cells 33
4.1. Basics of Electrochemical Impedance Spectroscopy (EIS) technique 35
4.2. J-V measurements and fitting 37
4.3. C-f and G/omega-f measurement and fitting 40
4.4. J-V and C-G/omega-f simulations 42
Chapter 5: Current-voltage and Impedance Spectroscopy analyses under different illumination conditions 48
5.1. Surface morphology and electronic properties of copper-doped NiOx 49
5.2. Surface morphology of MAPbI3 films formed on Cu-doped NiOx 50
5.3. J-V measurements and fitting 53
5.4. C-G/omega-f measurements and fitting 58
5.4.1. Light-intensity dependence of VOC 62
5.4.2. Dependence of low-frequency capacitance (Clf) on VOC 65
5.4.3. Dependence of high-frequency capacitance (Chf) on VOC 65
5.4.4. Dependence of resistances on VOC 68
5.5. SCAPS simulation model and results 70
Chapter 6: Hysteresis and effects of electrical poling 86
6.1. Scan rate and scan direction dependence of J-V characteristics 88
6.2. Effects of electrical poling on J-V curves 94
6.3. Effects of pre-poling bias on J-V curves 98
6.3.1. Transient dark current measurements 98
6.3.2. Analyses by two-diode model 100
6.3.3. Analyses by SCAPS simulations 110
Chapter 7: Summary and future works 117
7.1. Summary 117
7.2. Future works 119
Bibliography 120
Appendix 134
