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標題: | 染料敏化太陽能電池製程優化與金屬螯合物添加劑對鈣鈦礦太陽能電池的影響探討 Facile Solution Dropping Method for Dyeing TiO2 Electrode of Dye Sensitized Solar Cells (DSSCs) with Enhanced Power Conversion Efficiency and the Effects of New Metal Chelates as Additives for Perovskite Solar Cells (PSCs) |
作者: | Shih-Chieh Yeh 葉世傑 |
指導教授: | 鄭如忠 |
關鍵字: | 二氧化鈦層,染料敏化太陽能電池,浸泡式,液滴式,光電轉換效率,錨定基,鈣鈦礦太陽能電池,金屬螯合物,氮??,一般型,反式,空間電流電荷,載子遷移率, TiO2,dye sensitized solar cells (DSSCs),immersion method,dropping method,anchoring group,perovskite solar cells (PSCs),metal chelates,4-methyl-[1.5]-naph- thyridin-8-ol (HmND),regular,inverted,space charge limited current (SCLC),charge carrier mobility, |
出版年 : | 2017 |
學位: | 博士 |
摘要: | 本論文以氟摻氧化錫透明導電膜 (FTO) 製作太陽能電池元件,研究主題分為兩部份。第一部份開發新型液滴式 (solution dropping method) 快速染料附著製程,製作高效率染料敏化太陽能電池 (dye-sensitized solar cells; DSSCs)。第二部份研究以氮喹啉 (4-methyl-[1.5]-naph- thyridin-8-ol; HmND) 配位基形成的金屬螯合物,作為鈣鈦礦太陽能電池添加劑 (perovskite solar cells; PSCs) ,並分析此類添加劑對元件效率的影響。
首先,第一部份以新型液滴式 (new solution dropping method) 進行染料附著,達到染料敏化太陽能電池效能優化的目的。有別於傳統的浸泡式 (dipping method) 的方法,需長時間浸泡 (2-24小時) 才能得高效率的元件。本論文液滴式的方法,以高極性及高濃度的溶液將染料快速附著於二氧化鈦 (TiO2) 表面上,製備元件的時間將縮短至10分鐘以內,染料附著的程序更只需5分鐘。以一個0.16 cm2的元件為列,所需的染料量將為傳統浸泡式的1/10。除此之外,液滴式的方法可以避免染料浪費及節省溶劑讓製程更環保。 液滴式快速染料附著法,選擇三種典型的染料製作元件,光電轉換效率 (power conversion efficiency; PCE) 皆可以達到很好的效果。包括第一種釕 (Ru) 金屬錯合物N719,平均光電轉換效率可達8.5% (浸泡式8.1%)、第二種有機推拉式分子 1P-PSS,平均效率可達6.6% (浸泡式5.9%)。效果最好的大環分子ATT,其平均相對於浸泡式更增加了60% (從4.1% 增加到6.7%)。經過一系列的分析,例如染料附著密度測試 (dye loading density)、電子顯微鏡碳/鈦原子訊號比值偵測 (SEM EDS for C/Ti) 分析,可發現新型液滴式的方法使染料高密度分散,並且更深入TiO2層。利用暫態光電壓/光電流衰減訊號 (Transient Photovoltage/Photocurrent; TPV/TPC) 量測,證明液滴式的元件有比較長的電子/電洞再結合的時間及較快的載子傳輸速度,如此能減少光電流的損失。為了進一步液滴式的優勢,以新開發的2,6取代的BODIPY染料進行液滴式元件的製作,其中MPBTTCA的液滴式元件效率最高效率可達6.4%。其中含有新錨定團基 (anchoring group) 的 MPBT-pyO,液滴式的元件效率達3.3 %,足足高出浸泡式元件的0.3%有10倍之多。其他的BODIPY染料利用液滴式製作元件,也呈現了相當好的效果。這也顯示此液滴式的方法,對於測試新的染料是相當快速且便宜實用的篩選方式。 第二部份,利用本實驗室已開發的一系列的金屬螯合物做為鈣鈦礦薄膜添加劑,製備一般式 (regular) 及反式 (inverted) 兩種型式的鈣鈦礦太陽能電池。此類添加劑以氮喹啉 (4-methyl-[1.5]-naph- thyridin-8-ol; HmND) 的配位基製備金屬螯合物,其中金屬中心包括鋅 (ZnII), 鎂 (MgII), 鋁 (AlIII), 鎵 (GaIII), 銦 (InIII) 及 鉿 (HfIV) 等。此類螯合物金屬螯合物上的氮原子會與鈣鈦礦結構薄膜產生作用力,達到修飾鈣鈦礦薄膜的效果。 本研究中將0.4 wt% 金屬螯合物 (重量百分比於碘化鉛(PbI2)) 的濃度加入碘化鉛的溶液中,以二步法製備鈣鈦礦薄膜。各金屬螯合物對於鈣鈦礦薄膜性的影響可包括: (1) 含有不同金屬原子,(2) 氮喹啉上的氮 (N) 具有孤對電子,及(3) 不同的分子構形 (meridional or facial) 都是造成鈣鈦礦薄膜及元件電性上的差異的原因。其中,鈣鈦礦結構中的鉛離子 (Pb2+) 或碘離子 (I-) 離子與各金屬螯合物之間的作用力,可透由比對金屬螯合物有無加入PbI2或甲基碘胺 (MAI) 的氫核磁共振光譜 (1H-NMR spectra) 及螢光光譜 (photoluminescence spectra; PL) 証明了作用力的存在並了解發生的位置。利用場發射電子顯微鏡 (FE-SEM) 與 X射線繞射光譜儀 (X-ray diffraction patterns) ,鑑定添加金屬螯合物的鈣鈦礦薄膜在表面形態及結晶組成都與未添加的薄膜不同程度的差異。此外,藉由鈣鈦礦薄膜的吸收光譜及低功率光電光譜儀 (AC2) 測得的數據定義此類鈣鈦礦薄膜的能階,薄膜的電子最高占有軌域 (HOMO) 能階從5.44 eV降低至5.5-5.6不等。 此一系列含有金屬螯合物鈣鈦礦太陽能電池,提升了一般式及反式的元件光電轉換效率都有提升。其中以MgmND2-based的元件有最好的效果。一般式元件最高轉換效率來到12.12% (無添加為9.95%)。主要是MgmND2-based的鈣鈦礦元件VOC增加至1.06V ,較無添加的元件0.94V高。另一方面,MgmND2-based反式的元件也可達14.54% (無添加為12.32%)。其他的金屬螯合物添加劑所製作的元件,也有增加的效果。本研究亦利用空間電流電荷 (space charge limited current; SCLC) 的方法評估此一系列的鈣鈦礦薄膜的載子遷移率 (charge carrier mobility)。初步了解,不同的金屬螯合物添加劑產生的作用,的確對於鈣鈦礦薄膜電性造成的相當程度的影響。鈣鈦礦太陽能電池的效率高,則電子/電洞的遷移率比較接近。最後,為了了解各金屬螯合物添加劑對元件穩定性的影響。以反式元件放置於常溫下儲存350小時,觀察添加劑長時間對鈣鈦礦薄膜是否有利。可以發現在350小時後,元件的遲滯效應有緩和的趨勢。其中又以分子對稱性高的fac-InmND3的元件長時間穩定性表現較佳。 A simple solution dropping method was established for sensitizing TiO2 in the fabrication of dye-sensitized solar cells (DSSCs). Comparing with conventional solution dipping (or immersion) method, solution dropping method is very fast, less than ~5 minutes vs >2~24 hours typically required in solution dipping method. There are much less organic solvent and dye substance (95% less) used in the dyeing TiO2 process and hence significantly less disposal of chemical waste from the device fabrication. Therefore, our facile and very fast solution dropping method is a greener and more sustainable process than conventional dropping method. Moreover, the solution dropping method is superior to solution dipping method in terms of power conversion efficiency (PCE) of the device. We have acquired compelling evidences, dye uptake assessment of TiO2 electrode, depth profile assay by SEM-EDX, and charge dynamic characteristics from transient photocurrent/photovoltage analysis, indicating the elevated dye loading of TiO2 electrode is the main cause of increasing short-circuit current and hence the PCE of DSCs. Three types of dye were used in this study to demonstrate the superiority of solution dropping method. They are classical N719 (ruthenium transition metal complex), 1P-PSS (metal free organic dye), and the newly synthesized ATT (a -pyrrole carbon-conjugated zinc tetraphenylporphyrin). With solution dropping method, the average PCEs (from thirty or forty tested devices of each dye) are all improved, 8.1% to 8.5%, 5.9% to 6.6%, and 4.1% to 6.7% for N719, 1P-PSS, and ATT, respectively. Further more, high performance 2,6-subsititute BODIPYs were also developed by solution dropping method. The best PCE of MPBTTCA could be achieved to 6.4%. Especially for the PCE of MPBT-pyO device by dropping method was ten times higher than it by dipping method. This indicates the new solution dropping method could be a feasible method for all dying process. On the other hand, the incorporation of additives to perovskite layers is one of the most effective strategies to optimize perovskite solar cells (PSCs). Herein, we developed a series of 8-methyl-1,5-naphtyridin-4-ol (HmND) metal chelates as additives for both regular (mesoporous TiO2-based) and inverted (nickel oxide; NiOx-based) PSCs. These metal chelate additives including Zn(II), Mg(II), Al(III), Ga(III), In(III), and Hf(IV) metal cations, and the free ligand HmND were respectively incorporated into CH3NH3PbI3 films by a two-step method. The interaction of naphtyridine on metal chelates with lead and iodine ions in DMSO solution was first investigated by 1H-NMR and photoluminescence (PL) spectra. Moreover, the morphology of CH3NH3PbI3 affected by the chemical structure of metal chelates was investigated by field emission scanning electron microscopy (FE-SEM). A featureless morphology was found for the pristine CH3NH3PbI3 films. For the films incorporated with metal chelates, leaf-like or rose petal-like morphologies were observed on mesoporousTiO2 scaffold substrates, whereas coral reef-like morphologies were found on NiOx substrates. Apart from that, HOMO level shifts and microstructure phases of these modified CH3NH3PbI3 films were also thoroughly investigated. These metal chelate-based PSCs exhibited a significant enhancement in open-circuit voltage (VOC) (maximum 1.06 V vs 0.94 V for the pristine sample). The maximum power conversion efficiency (PCEmax) of Mg chelate-based devices were 12.12% and 14.54% for regular and inverted PSCs, respectively. In addition, the charge transport properties of metal chelate-based devices were evaluated by space-charge-limited-current (SCLC) method. To understand the long-term stability of respective metal chelate-based devices, these photovoltaic parameters were recorded for 350 h. The facial form in chelate-based solar cells were able to exhibit 12% of PCE increase when compared to their original values. |
URI: | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/20358 |
DOI: | 10.6342/NTU201704274 |
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顯示於系所單位: | 高分子科學與工程學研究所 |
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