高效率高分子/奈米粒子太陽能電池

High Efficiency Polymer/Nanoparticle Solar Cells

廖學中(Hsueh-Chung Liao)

指導教授 ： 林唯芳

共同指導教授 ： 陳永芳 ； 曹正熙(Cheng-Si Tsao)

國立臺灣大學/工學院/材料科學與工程學研究所/博士(2013年)

https://doi.org/10.6342/NTU.2013.01312

摘要

高分子太陽能電池具備有溶液製程，低成本，可撓曲，質輕，半透明等優點，成為極具潛力的替代能源，提升高分子太陽能電池的元件效率以及元件穩定性為現階段最重要的目標，為了達成此目標，本論文研究重點包高分子/奈米粒子的異質接面薄膜的三維奈米結構的調控以及量化分析，高穩定性高分子/無機奈米粒子之開發，新型低能階差奈米粒子的合成與開發，以及串疊型太陽能池的製程與研究。
調控高分子/奈米粒子的異質接面薄膜的三維奈米結構，可以有效的提升元件的能量轉換效率，文獻中在製程上對於效率增加的調控已相當成熟，但相關的基礎知識，包括奈米結構的變化機制以及其與元件效率量化性關係至今仍非常有限，因此，本研究工作利用掠角廣角/小角散射技術，建立一套對於異質接面薄膜結構的量化分析技術，我們利用此技術分析P3HT/PC61BM異質接面薄膜在熱退火，溶劑退火，以及導入無機奈米粒子等製程處理上的結構變化，以及PCPDTBT/PC71BM異質接面薄膜在溶劑添加劑影響下的奈米結構變化，此技術之建立以及相關基礎知識的研究將有助於往後元件製程參數調控以及相關合成工作的設計。
然而，富勒烯衍伸物仍有熱穩定性較差的問題，因此，為了增加異質接面薄膜的穩定度，我們製作高分子/二氧化鈦粒子的混摻薄膜，並且將其用於反式的元件結構上，我們成功的製程出一個高效率，並且在大氣下無封裝狀態中極為穩定的混摻太陽能電池。最後，由於二氧化鈦奈米粒子對於可見光以及近紅外光無法進行吸收，因此我們合成具有低能階差的半導體奈米粒子銅鋅錫硫，我們開發出一套單鍋直接升溫的合成法製備銅鋅錫硫奈米粒子溶液，我們有系統地研究此種特殊奈米粒子成長的機制及其性質，並期望其可應用在相關能源領域。
串疊型太陽能電池可克服單電池在電流以及電壓上的限制，以達到更高效率，我們在此研究中對於串疊型電池的製程以及元件物理進行探討，我們首先由前子電池的製程開始研究，並且了解中間連階層與異質接面層的相容性，我們並且開發出利用銫化合物摻雜於氧化鋅奈米粒子與高分子的複合物中，作為串疊型電池的中間層，我們最終成功堆疊出能量轉換效率達6.5%之串疊型電池，此研究成果對未來欲達更高效率為重要的基底。我們期望藉由研究論文，可以整合形態學研究，材料合成開發，以及元件製程等三方面，對於朝向高效率以及高穩定性的高分子太陽能電池有突破性的貢獻。

關鍵字

高分子太陽能電池 ； 塊狀異質接面 ； X光散射 ； 串疊型太陽能電池 ； 無機奈米粒子 ； 有機無機混摻材料 ； 無機奈米粒子

並列摘要

Polymer solar cell has attracted considerable attentions for tackling the energy problem owing to the advantages of solution process, flexibility, light weight, low cost, semi-transparency, etc. Improving power conversion efficiency (PCE) and device stability are the general goals for competing with fossil energy source and other photovoltaic (PV) technologies. In order to achieve the goals, the present research focuses on the topics of control and quantitative characterization of three dimensional nanostructures in polymer/nanoparticle bulk heterojunction (BHJ) solar cells, development of high stability polymer/inorganic hybrid BHJ solar cells, synthesis and development of novel low band gap inorganic nanocrystals, and investigations of tandem device structure.
Various processing strategies have been developed for improving PCE by controlling the 3-D nanostructures of BHJ. However, how the BHJ nanomorphology is tailored and the quantitative correlations to the enhanced PCEs are still limited. We aim to establish a quantitative evaluating methodology with associated fundamental knowledge of BHJ nanostructures. We developed an improved simultaneous grazing incidence wide/small angle X-ray scattering (GIWAXS/GISAXS) analysis technique. This method has been applied to resolve the structural evolutions of self-organized P3HT/PC61BM blends tuned by thermal annealing, solvent-vapor annealing, incorporation of inorganic nanoparticles (INPs) respectively and PCPDTBT/PC71BM blends tuned by solvent additives. We present quantitative studies of the BHJ nanostructures and an evaluating methodology which is helpful for further improving solar cell performance and associated processing design and materials synthesis.
The fullerene based solar cell has the disadvantages of low physical and thermal stability. In order to improve the device stability, the P3HT/TiO2 hybrids are alternatively employed as the BHJ layer that is implemented in inverted device architecture. An all solution processed and air-stable P3HT/TiO2 hybrid inverted hybrid solar cell is successfully developed, showing PCE of 1.2% and significant stability in ambient condition without encapsulation (less than 10% loss over 1000 hours). Furthermore, for addressing the issue of no absorption of TiO2 nanocrystals in visible and near infrared regions, we tried to develop copper zinc tin sulfide (CZTS) nanocrystals with low bandgap. We developed a facile one-pot heat up process to prepare the CZTS nanocrystal suspension which is potential for practical photovoltaic applications.
The tandem structure is promising for further improving the device performance overcoming the trade-off between output current and voltage in single junction devices. Herein the processing and device physics of tandem cells were systematically studied. We started with the fabrication of front sub-cell and addressing the problem of compatibility between inter-connection layer and BHJ layer. Additionally, composites of ZnO nanoparticles and PVP doped by CsCO3 was developed and applied in single and tandem solar cell to reduce the carrier recombination and increase the device performances. A 6.5% PCE of tandem cell was attained with little loss in output voltages from the sub-cells which indicated the successful fabrication of a tandem cell with efficient inter-connection layer. The established processing for tandem cell in the present work is extremely important for the following work aiming on higher power conversion efficiency. It is our hope that the results demonstrated in this dissertation will contribute to the advance of polymer based photovoltaics in the aspects of morphological investigation, materials development and device processing toward practically realizing the organic photovoltaic technology.

並列關鍵字

polymer solar cell ； bulk heterojunction ； X-ray scattering ； tandem cell ； orgnanic/inorganic hybrid ； inorganic nanocrystal

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