Influence of Heat Treatment Condition on Performance of Ag Metal Contact in Crystalline Silicon Solar Cells
- 주제(키워드) Metallization , front grid width , specific contact resistance , Ag crystallites , junction leakage current , silicon solar cells
- 발행기관 고려대학교 대학원
- 지도교수 김동환
- 발행년도 2012
- 학위수여년월 2012. 2
- 학위구분 석사
- 학과 일반대학원 신소재공학과
- 원문페이지 93 p
- 실제URI http://www.dcollection.net/handler/korea/000000033993
- 본문언어 영어
- 제출원본 000045696995
초록/요약
The effect of the peak firing temperature on the contact properties between Ag metal and silicon (n+ emitter) was investigated. The factors that control the specific contact resistance were as follows: (1) Ag coverage fraction, (2) thickness of glass layer and (3) etching depth on n+ silicon (emitter). As a result, we obtained a satisfactory specific contact resistance of 8.27 m？？cm2 at the optimum firing temperature (720 ？C). In the contact process, Ag and other metallic impurities can diffuse into the silicon and cause a trapping effect by forming shallow trap sites. The shallow trap density, extracted by QSSPC, increased with the peak firing temperature. The J02 also increased with the peak firing temperature, which could be due to the increased trap density. The specific contact resistance influences the series resistance, which creates a loss in the fill factor. The fill factor losses caused by the series resistance and the junction leakage current were 5.5 % and 0.879 %, respectively. Consequently, the efficiency and fill factor were 17.47 % and 77.5 % at the optimum firing temperature (720？C). To study the effect of the difference in contact resistance between the finger and the busbar, the contact properties of front grid according to grid widths were studied. The difference of the contact width affects the thermal uniformity which causes the metal coverage on the silicon substrate to be different. For this reason, the smaller widths (finger-sized) formed optimal contacts at low firing temperatures than the larger widths (busbar-sized). According to PC1D simulations, industrial silicon solar cells lost 0.06% efficiency because of the difference in the contact grid widths. Wider grids (busbar-sized) also increase the junction leakage current. Therefore, the difference of grid width between the finger and the busbar should be minimized to obtain high efficiency silicon solar cells.
more목차
Chapter 1. Introduction - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 1
Chapter 2. Theoretical Background - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 5
2.1 Solar Cells - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 5
2.1.1 Operating principle of solar cells - - - - - - - - - - - - - - - - - - - - - - - - 5
2.1.2 Current-Voltage characteristics - - - - - - - - - - - - - - - - - - - - - - - - - 9
2.1.3 Solar cells parameters - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 12
2.1.4 Loss mechanism of solar cells - - - - - - - - - - - - - - - - - - - - - - - - - - 15
2.2 Silicon Solar Cells - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 17
2.2.1 Screen printed solar cell - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 22
2.3 Recombination - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 25
2.3.1 Surface recombination - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 25
2.3.2 Bulk recombination process - - - - - - - - - - - - - - - - - - - - - - - - - - - 26
2.4 Solar Cell Metallization Techniques - - - - - - - - - - - - - - - - - - - - - - - - - 29
2.4.1 Photolithography Contacts - - - - - - - - - - - - - - - - - - - - - - - - - - - - 29
2.4.2 Buried-Contact Technology - - - - - - - - - - - - - - - - - - - - - - - - - - - - 30
2.4.3 Screen-Printing Technology - - - - - - - - - - - - - - - - - - - - - - - - - - - 30
2.4.4 The Screen-Printed Paste Firing Process - - - - - - - - - - - - - - - - - - - 33
2.4.5 Contact Formation Mechanism of front metallization - - - - - - - - - 37
2.4.6 Current Transport Mechanisms - - - - - - - - - - - - - - - - - - - - - - - - - 39
Chapter 3. Effect on Ag Metal Contacts in Silicon Solar Cells under Different
Heat Treatment Conditions - - - - - - - - - - - - - - - - - - - - - - - - - - - -
42
3.1 Introduction - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 42
3.2 Experimental procedure - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 42
3.3 Results and discussion - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 43
3.4 Conclusions - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -- 62
Chapter 4. Ag contact properties with different front grid widths
for silicon solar cells - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
63
4.1 Introduction - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 63
4.2 Experimental procedure - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 63
4.3 Results and discussion - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
64
4.4 Conclusions - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 74
References - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 75
