高效率新穎太陽能電池研究

High Power Conversion Efficiency Based on Solar Cell with Novel Structures

陳建廷(Chien-Ting Chen)

指導教授 ： 陳永芳

國立臺灣大學/理學院/物理研究所/博士(2014年)

https://doi.org/10.6342/NTU.2014.00228

摘要

中文摘要
近年來，隨著石化燃料的缺少，無論是科學界和工業界都傾注了自己的努力在發展可再生能源。在所有的可再生能源中，太陽能電池已被廣泛研究的研究。在本篇論文中，我們報導了有關於有機-無機太陽能電池、矽基板太陽能電池和鈣鈦礦型太陽能電池的改進。利用有機-無機介面之間的修飾、使用磁性奈米線作為添加劑，以提高主動層內吸光高分子的排列，進而提高了元件的效率。另一方面，利用天然的葉綠素A，來提高矽基板太陽能電池的效率。最後，經由一系列改變金的奈米結構以及濃度添加到電子傳輸層，進而提升鈣鈦礦太陽能電池的效率。本論文包含了四大主題，其摘要如下:

1. 使用不含金屬的新穎合成共軛聚合物修飾有機/無機介面
有機/金屬氧化物混摻太陽能電池的研究中，有機/無機介面之間的的性質，是個關鍵的研究主題。本章節中，我們合成了一種共軛聚合物(O3HT-(Br)NH2)，將此種聚合物當作表面修飾劑，用於有機/氧化鋅奈米柱太陽能電池當中。此聚合物與主動層當中的吸光有機高分子相比長度大約只有高分子的十二分之一。利用此種聚合物修飾氧化鋅奈米柱，可發現在修飾過後，元件的電子遷移率有顯著的提升。因為此種共軛聚合物本身的特性，修飾過後，元件中載子傳輸特性進而可以獲得明顯的改進。最後在元件量測中，發現到元件的光電流可以提升將近35%左右。

2. 增進吸光有機高分子的排列:添加磁性奈米材料以及外加磁場
本章節中，在反式有機太陽能電池中，添加些許的鐵鉑合金，再利用外加磁場以增進有機高分子的排列。在吸光主動層慢乾的過程中，因為鐵鉑合金本身帶有磁性，在外加磁場下，可增加有機高分子的排列。利用光學量測可發現不論是垂直基板(out-of-plane)的方向，或是平行基板(in-plane)的方向，反射係數都有所下降，特別是在垂直基板(out-of-plane)的方向。有如此特異的光學異向性，再利用高功率X光繞射分析儀，可證明利用外加磁場以及添加磁性奈米柱於反式有機太陽能電池中，會增加有機高分子的排列，進而增進元件的效率。最後在元件量測中，可發現元件的效率提升將近57%左右。此種新穎的方式，將可廣泛運用在有機混合光電元件系統中。此外，在製作元件的過程中，因其更加簡單、低溫、少耗能的特性；也為高效率可彎曲有機太陽能電池開創了一個新的製程方式。

3. 利用矽藻萃取物增進矽基板太陽能電池的集光性
本實驗中，我們利用一個簡單的方式，利用矽藻萃取物當作矽基板太陽能電池的抗反射層。實驗過程中可以發現，在波長350奈米到1100奈米，矽藻萃取物會提高反射系數7%左右。此外，也發現到矽藻萃取物會吸收短波段光子的能量，進而轉換放出可見光光子。此種效應(downconversion)以及抗反射的效果，將會提高矽基板光電流的大小，以及提升太陽能電池的效率。如此有效、環保的方法將可以大幅運用在大面積矽基板太陽能電池製成方式中。

4. 藉由表面電漿的效應以增進鈣鈦礦太陽能電池效率
在本章節中，我們提供了一個新穎的方式來增進鈣鈦礦太陽能電池的效率。在電子傳輸層中，混入少量的奈米金；再藉由改變奈米金的形貌，來調控表面電將的位置，進而來增進元件的效率。在製作元件整個過程中，電子傳輸層、只要吸光層，溫度都是處於在低溫狀態之下。在最後量測元件效率時，可發現添加奈米金的元件，整體效率比標準元件可以提高將近10%左右。如此簡單、低溫製作元件的方法，將更加適合應用到可彎曲性鈣鈦礦太陽能電池上。

關鍵字

混摻太陽能電池 ； 氧化鋅 ； 表面修飾 ； 鐵鉑合金 ； 矽基板太陽能電池 ； 鈣鈦礦太陽能電池

並列摘要

Abstract
Recently, with the shortage of nature fossil, both scientific and industrial communities have devoted their efforts in developing renewable energy. Among the renewable resources, solar cells have been intensively studied nowadays. In this thesis, we report the improved efficiency of organic-inorganic hybrid solar cells, Si solar cells, and halide perovskite solar cells. With the organic-inorganic interface modification and using magnetic NWs as additive, we are able to improve organic matter arrangement, and thus enhance the efficiency of the devices. On the other hand, we use eco-friendly chlorophyll A to improve the efficiency of silicon based solar cells. Finally, a series of organic-inorganic halide perovskite solar cells with addition of spherical, rod Au nanostructures to the electron-transporting compact layer have been investigated. The highlight of our scientific achievement is briefly described as follows.

1. Effects of metal-free conjugated oligomer as a surface modifier in hybrid polymer/ZnO solar cells
The interface property has been one of the critical issues in developing hybrid polymer/metal oxide solar cells. We synthesize a conjugated oligomer, an amine-and bromine-terminated 3-hexyl thiophene (O3HT-(Br)NH2), to modify the ZnO-nanorod (ZnO-NR) surface in hybrid polymer/ZnO-NR photovoltaic cells. This oligomer is of the same repeat unit structure as and ~1/12 the contour length of the light-harvesting polymer. In addition to passivate the NR surface, the presence of this conjugated oligomer enhances the electron mobility, and drives larger hole density toward the anodic surface for collection. The improved charge transport property of the hybrid is presumably a result of modulating the nano morphology of the bi-carrier transport network induced by the conjugated oligomer. As a result, there is a large enhancement in photocurrent and photovoltage leading to an improved device performance of ~ 35%.

2. Magnetic-Field Annealing of Inverted Polymer:fullerene Hybrid Solar Cells with FePt Nanowires as Additive
We demonstrate a novel annealing method to improve the polymer chain ordering of poly(3-hexythiophene):(6,6)-phenyl C61 butyric acid methyl ester (P3HT:PCBM) blend triggered by a small amount of FePt nanowires (NWs). By applying a magnetic field (B-field) perpendicular to the substrate during the solvent drying process, the resulting P3HT:PCBM:FePt NWs film exhibits a relatively lower reflectance intensity in both in-plane and out-of-plane directions and becomes highly optical anisotropy with a preferential out-of-plane orientation. The improved polymer chain ordering revealed by the optical anisotropic measurements leads to more than 57% increment in the power conversion efficiency (PCE) of the devices. The method of magnetic-field assisted annealing is simple and can be applied to a wide variety of polymer blend systems. Additionally, it can be easily integrated into low-temperature and cost-effective fabrication processes, providing a new route for advancing flexible polymer solar cell development.

3. Improved light harvesting of surface textured Si solar cells using diatom extract
We demonstrate an effective approach to improve the light harvesting of silicon solar cells by incorporating the diatom extract as an antireflection coating. The diatom extract layer can suppress the overall light reflection up to 7% over spectrum regions of 350 – 1100 nm. Additionally, it also shows a strong photon downconversion effect within visible light regime. With both optical characteristics, the short circuit current is largely enhanced and hence the cell efficiency. The presented approach is simple, doable, suitable for large area application, and more importantly, it is eco-friendly.

4. Power conversion efficiency enhancement of organic-inorganic halide perovskite solar cells by addition of Au nanospheres and nanorods
We demonstrate a novel method to improve the organic-inorganic halide perovskite solar cells blend triggered by different morphologies amount of Au nanostructures. Addition of Au nanostructures with various morphologies into electron-transporting-layer of organic-inorganic halide perovskite solar cell increase the PCE as compared to the cell constructed without the addition of Au nanostructures. The increment is around 10% in the power conversion efficiency (PCE) of the devices. The method of fabricating organic-inorganic halide perovskite solar cells by sequential deposition and process of ZnO compact layer with low temperature is simple. Additionally, it can be easily integrated into low-temperature and cost-effective fabrication processes, providing a new route for advancing flexible organic-inorganic halide perovskite solar cell development.

並列關鍵字

hybrid solar cell ； ZnO ； interface modification ； FePt ； Si based solar cell ； Perovskite solar cell

參考文獻

5. Green, M. A. Solar cells: Operating Principles, Technology and System Applications; The University of New SouthWales: Sydney, Australia, 1998.

7. Nelson, J. The Physics of Solar Cells; Imperial College Press: London, 2003.

9. Green, M. A. Third generation photovoltaics: advanced solar energy conversion; Berlin; New York: Springer, 2003.

13. T. C. Sum , and N. Mathews, Energy Environ. Sci., Advance Article (2014).

14. Gary Hodes, Perovskite-Based Solar Cells, Science 342, 317 (2013)