混成型太陽能電池之光物理與物理性質研究

Photophysical and physical properties of hybrid solar cells

楊博帆(Po-Fan Yang)

指導教授 ： 林皓武

國立清華大學/工學院/材料科學工程學系/碩士(2014年)

摘要

本論文主要研究方向為有機/無機混成型太陽能電池的物理與光物理性質探討，其中包括以有機染料作為吸光材料的染料敏化太陽能電池、無機矽晶作為主要吸光層的矽晶有機/無機混成太陽能電池，以及使用有機/無機混成晶體材料CH3NH3PbI3作為吸光層的新穎鈣鈦礦有機/無機混成太陽能電池，進行元件的基本光電性質與瞬態光電壓電流的量測分析，探討內部載子反應機制與效率表現之關聯性。此外，我們也關心鈣鈦礦薄膜在不同底部材料上的表面結構變化與元件效率表現。
　　第一章部分，介紹近代太陽能電池的發展史，其中包括混成型太陽能電池的研究回顧、所遭遇的瓶頸與未來發展方向。
　　第二章部分，概述混成型太陽能電池的工作原理與元件基本光電特性，並介紹元件的電流密度-電壓量測與外部量子效率頻譜分析，以及瞬態光電壓電流量測系統。
　　第三章部分，為染料敏化太陽能電池的基本光電性質與瞬態光物理性質分析，我們使用瞬態光電壓電流量測系統來分析釕金屬、鋨金屬錯合物染料，以及純有機D-A-π-A型染料，並發現到染料分子結構引入立障基團能有效抑止TiO2表面電子與電解質發生再覆合反應，然而，過低的染料吸附量也可能降低染料分子對TiO2表面的保護效果，當兩項因素達到平衡後，才會有效的提升元件效率表現。
　　第四章部分，我們使用瞬態光電壓電流量測系統來分析矽晶有機/無機混成太陽能電池中SiOx的鈍化效果與元件效率表現的關係，其中，發現SiOx會降低元件中trap-state density的發生，並與元件效率表現有很大的對應關係，然而，過厚的SiOx也會降低載子傳輸能力，影響效率表現。
　　第五章部分，對於新穎鈣鈦礦有機/無機混成太陽能電池的研究，我們使用自行合成的前驅反應物CH3NH3I，並以溼式旋塗製程高效率的鈣鈦礦有機/無機混成元件，效率能有10 %以上的表現。此外，我們選擇ZnO作為電子傳輸層與under-layer材料，但鈣鈦礦薄膜的表面結構較為粗糙且有孔洞產生，因此元件效率表現不佳。為改善鈣鈦礦薄膜的表面結構，我們使用真空蒸鍍製程，ZnO仍然是不適合鈣鈦礦的under-layer材料，但觀察到在MoO3、TiO2、PEDOT上，鈣鈦礦都能有覆蓋完整且平整的薄膜表現，預期未來以此製程元件能有不錯的效率表現。

關鍵字

瞬態光物理分析 ； 染料敏化太陽能電池 ； 鈣鈦礦太陽能電池

並列摘要

In this thesis, we focus on the photophysical and physical properties of hybrid solar cells, including dye-sensitized solar cells (DSSCs), Poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS)/Si organic/inorganic hybrid solar cells and novel perovskite solar cells. We utilized a series of measurement systems to analyze the charge recombination process and carrier concentration in DSSCs and organic/inorganic hybrid solar cells. We investigated the detailed physical properties of perovskite thin films deposited on different under-layer materials. The relationship between surface morphology of perovskite thin films and the device power conversion efficiencies is also discussed.
In the first chapter, we briefly review the history of photovoltaics, especially recent development of hybrid solar cells.
In the second chapter, the operation mechanisms and photovoltaic characteristics of the hybrid solar cells are described in detail. The measurement setups and principles of current-voltage curve, external quantum efficiency analysis, and transient photovoltage/photocurrent measurements are also shown in this chapter.
In the third chapter, the photophysical measurement systems were employed to analyze the Ruthenium(II)-based, Osmium(II)-based and metal-free organic sensitizers in DSSCs. We find that the addition of spacial barrier in molecular structures can slow down the charge recombination from TiO2 to the electrolyte and enhance photovoltage. Besides, dye loading also affects the charge recombination. These two factors need to be considered in the future molecular design of high efficiency dye sensitizer.
In the fourth chapter, the transient photovoltage/photocurrent measurements were utilized to investigate the influence of trap-state density on power conversion efficiency of PEDOT:PSS/Si organic/inorganic hybrid solar cells. We find that the SiOx passivation layer decreases the amount of trap-state density. However, thicker SiOx becomes a barrier for carrier transportation due to its non-conducting property.
In the fifth chapter, we manufactured perovskite solar cells from the home-made precursor reactant CH3NH3I. We used planar ZnO thin films as an electron transporting under-layer layers. Poor efficiency was found in solution casted devices with the ZnO under-layer due to the non-uniform surface morphology of perovskite thin films. The surface morphology and surface coverage can be largely improved by vacuum evaporation of perovskite thin films on MoO3, TiO2, and PEDOT:PSS under-layers. We believe that efficient perovskite hybrid solar cells can be realized by utilizing these perovskite/under-layer pairs.

參考文獻

96 A. Ibrahim, Analysis of Electrical Characteristics of Photovoltaic Single Crystal Silicon Solar Cells at Outdoor Measurements, Smart Grid and Renewable Energy, 2011, 02, 169.

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