Hydrothermal Synthesis of Branched ZnO Nanowire Array as an Effective Photoanode for Quantum-Dot-Sensitized Solar Cells

학위논문 (석사)-- 서울대학교 대학원 : 재료공학부, 2014. 2. 박병우.I have focused on the synthesis of branched ZnO nanowires and the understanding of the growth kinetics during my thesis. Furthermore, the branched ZnO nanowire array was introduced as a photoelectrode of a quantum-dot-sensitized solar cell, and the correlation between the nanostructures and solar cell performance was investigated in terms of both optical (light trapping) and electrical (charge recombination) characteristics. Three-dimensional branched ZnO nanowires were synthesized by a seed-mediated hydrothermal growth. The fast growth-rate of (001) direction was possible due to the anisotropic nature of ZnO and the capping agents blocking a lateral growth of nanowire. About two-fold enhancement of power conversion efficiency (PCE) was obtained by growing secondary branches, and both short-circuit current and open-circuit voltage were enhanced. Highly increased surface area of photoelectrode, resulting in higher light harvesting from increased quantum-dot loading amount, and the higher diffused reflectance was observed due to enhanced light-scattering of 3D structure. In addition, electrochemical impedance spectroscopy and open-circuit voltage decay revealed the reduced recombination and higher lifetime of branched ZnO nanowires.Abstract i List of Figures iii List of Table ⅵ Chapter 1. Overview 1.1. Quantum-Dot-Sensitized Solar Cells 1 1.2. Zinc Oxide as a Photoelectrode Material 8 1.3. References 17 Chapter 2. Hydrothermal synthesis of branched ZnO nanowire array as an effective photoanode for quantum-dot-sensitized solar cells 2.1. Introduction 21 2.2. Experimental Section 23 2.3. Results and Discussion 26 2.4. Conclusion 45 2.5. References 46 국문 초록 50Maste