Study on a Transparent Back-Contact Electrode of a Bifacial CdTe Solar Cell
Study on a Transparent Back-Contact Electrode of a Bifacial CdTe Solar Cell
- 주제(키워드) solar cell
- 발행기관 고려대학교 대학원
- 지도교수 김지현
- 발행년도 2019
- 학위수여년월 2019. 2
- 학위구분 석사
- 학과 대학원 화공생명공학과
- 원문페이지 112 p
- 실제URI http://www.dcollection.net/handler/korea/000000083314
- UCI I804:11009-000000083314
- DOI 10.23186/korea.000000083314.11009.0000826
- 본문언어 영어
- 제출원본 000045978897
초록/요약
Solar energy received significant attention in recent years due to growing demands for pollution-free and sustainable energy resources. Cadmium telluride (CdTe) thin-film solar cells are one of the commercialized solar cells, owing to their short energy pay-back time and low fabrication cost. Researches on renewable energies are focused on reaching a higher levelized cost of electricity (LCOE). Conventional mono-facial structure of solar cells could utilize the incident light through only one side of the device. Solar cells with bifacial configuration, on the contrary, could use the incident light coming through both sides of the device. By using solar energy more efficiently, bifacial solar cells can generate more power per unit area. In this dissertation, bifacial CdTe solar cells using transparent back contacts are investigated. Copper nanowires (CuNWs) and indium tin oxide (ITO) are considered as a good transparent electrode because of its high conductivity and high transparency. Also, Cu in the back contact could reduce the series resistance of the device and enhance efficiency. CuNW/ITO hybrid electrode was introduced as a back contact of CdTe solar cell. To optimize the back contact, composite electrodes using different CuNW contents are investigated. The best average efficiency of 10.0% and 0.6% on front-side and rear-side illumination are achieved using CuNW/ITO back contact. Graphene possesses superior properties as a transparent electrode. Moreover, the high work function of graphene makes it a good candidate of back contact to CdTe solar cell. Mechanical polishing was conducted to reduce the roughness of the as-deposited CdTe surface. Single layer graphene was transferred on the polished CdTe as a back contact. To finish the back contact, ITO was sputtered. With graphene-based back contact, an average total efficiency of 10.1% was obtained. In conclusion, CuNW/ITO and graphene/ITO electrode showed high potential as a back contact with bifacial CdTe solar cell.
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Contents
Abstract i
Contents iii
List of figures v
List of tables viii
1. Introduction 1
1.1. Motivation 1
1.2. Background 3
1.2.1. Transparent conducting oxide 3
1.2.2. Cadmium sulfide layer 5
1.2.3. Cadmium telluride layer 6
1.2.4. Back contact 7
1.2.5. Structures of CdS/CdTe thin-film solar cell 10
1.2.6. Bifacial CdTe solar cells 13
1.3. Originality 16
2. Theoretical background 18
2.1. P-N junction 18
2.2. Mechanisms of photovoltaics 22
2.3. Method of measuring conversion efficiency of solar cells 24
2.4. Current density-voltage characteristics of solar cells 28
2.5. Quantum efficiency characteristics 34
2.6. CdTe solar cells 37
2.7. Transparent back contact 41
2.7.1. Copper nanowire-based transparent back contact 42
2.7.2. Graphene-based transparent back contact 43
3. Bifacial CdTe solar cells using copper nanowire-based back contact 46
3.1. Introduction 46
3.2. Experimental details 48
3.3. Results and discussion 51
3.4. Conclusion 71
4. Bifacial CdTe solar cells using graphene back contact 72
4.1. Introduction 72
4.2. Experimental details 74
4.3. Results and discussion 77
4.4. Conclusion 89
5. Conclusion 90
6. Future work 92
References 94
