用於光電應用的鹵化物和無鉛鈣鈦礦的設計、合成和製造

Design, Synthesis and Fabrication of Halide and Lead Free Based Perovskites for Optoelectronics Applications

雷默漢(Mohammad Rameez)

指導教授 ： 刁維光 ； 洪政雄

國立交通大學/理學院/永續化學科技國際研究生博士學位學程/博士(2020年)

摘要

儘管現有鈣鈦礦太陽能電池擁有創紀錄的效率，但阻礙鈣鈦礦太陽能電池商業化關鍵點在於製造過程所使用的前驅物(鉛及其鹵化物)具有毒性。其毒性會致癌是眾所周知的事。另外，鉛基鈣鈦礦的穩定性是另一個值得關注的領域，鈣鈦礦穩定性容易受到水氣和氧氣所影響。為了解決這些問題，本論文關注於開發無鉛鈣鈦礦，如擬鹵化物或超鹵化物鈣鈦礦，此新型鈣鈦礦不僅可以提高穩定性還可用於太陽能電池或是催化反應。
本論文第一部分著眼於開發擬鹵化物硫氰酸根離子（SCN-）的新型鈣鈦礦，硫氰酸根離子（SCN-）的角色是取代鹵化物並作為Sn4 +的抑制劑。由於Sn–I鍵是最弱的鍵結，很容易受到空氣中水分和氧的影響。而擬鹵化物硫氰酸根離子已被證實可增加錫基鈣鈦礦的穩定性。本篇論文中我們使用無電洞傳輸層的碳電極作為元件，使用基礎材料FASnI3的最佳元件效率為0.9％，而FASnI（SCN）2的最佳元件效率是2.4％，提升了將近三倍，並具有更好的穩定性。優異的性能和穩定性是因為抑制Sn2 +氧化為Sn4 +，因為有了更強的鍵結強度，增強疏水性，進而抑制了元件中的電子電洞再結合。此外，在溶劑萃取（SE）+ 5％EDAI2方法中加入10％苯乙基碘化銨（PEAI）後，PEA0.1FA0.9SnI（SCN）2最佳元件的數據為JSC = 20.17 mA cm–2，VOC = 322 mV，FF = 0.572，光電轉換效率η= 3.73％。此元件還表現出優異可忽略的光電流-電壓遲滯現象和高再現性。
在第二部分中我們延伸了一部分的概念，合成了具有不同比例的四氟硼酸根、碘酸根的新型超鹵化物鈣鈦礦，並應用於介觀碳電極結構太陽能電池。我們根據平面波密度泛函理論（DFT）進行了量子化學計算，並探索鈣鈦礦系列FASnI3-x（BF4）x（x = 0、1、2和3）的結構和電子性質。阻抗和X射線光電子光譜指出，添加四氟硼酸錫取代SnI2可降低Sn4 +含量來抑制陷阱的再結合。與標準FASnI3太陽能電池相比，具有FAI和Sn（BF4）2等莫耳數的FASnI3-x（BF4）x元件的光電轉換效率提高了72％，並環境空氣條件下具備良好的光穩定性。
最後，我們運用了無鉛低能帶隙Cu-Sb雙重鈣鈦礦，透過C-H鍵的活化來催化苯的氧化。這是首次報導雙重鈣鈦礦催化苯的氧化。
我們預測這些研究有助於更了解鈣鈦礦太陽能電池，並為無鉛和擬鹵素鈣鈦礦材料提供可行的替代方案。

關鍵字

鈣鈦礦 ； 太陽能電池 ； 無鉛 ； 偽鹵素 ； 超鹵素 ； 催化反應

並列摘要

The key issues preventing the commercialization of the perovskite solar cells in spite of their record-breaking efficiencies is the toxicity of precursors employed in their fabrication. Carcinogenic effects of lead and lead based halide is well known. Additionally, stability of the lead based perovskite is another area of concern. It is easily affected by the presence of moisture and oxygen. To address these issues, this thesis focuses on developing novel perovskite employing lead free halides, pseudo-halides or superhalides perovskites that can improve the stability and can be employed for different applications such as solar cell or catalysis.
The first part focuses on novel perovskites employing pseudo-halide thiocyanate ion (SCN-) as replacement for halides and as an inhibitor of Sn4+. As the Sn–I bonds are the weakest link which is easily affected by the presence of moisture and oxygen, pseudo-halide thiocyanate ion has been demonstrated to alleviate the stability issues of Sn based perovskite. Hole transport material (HTM) free carbon (C) based devices fabricated with novel perovskite FASnI(SCN)2 showed about 3-fold rise in device efficiency (2.4%) with enhanced stability as that of the best FASnI3 (0.9%) based devices reported for the same device structure. The superior performance and stability are attributed to suppression of Sn4+ oxidation, stronger bond strength, enhanced hydrophobicity, and consequently inhibition of recombination process in the devices. Furthermore, after incorporation of 10% phenylethyl ammonium iodide with the solvent extraction (SE) + 5% EDAI2 approach, the PEA0.1FA0.9SnI(SCN)2 device gave the best photovoltaic performance with JSC = 20.17 mA cm–2, VOC = 322 mV, FF = 0.572, and overall efficiency η = 3.73%. The solar cells also exhibited remarkably negligible photocurrent–voltage hysteresis and high reproducibility.
Further we extended this concept to superhalides in 2nd part and synthesized novel superhalide-based tin perovskites with different tetrafluoroborate/iodide ratios and implemented them into solar cells based on mesoscopic carbon electrode architecture. We carried out quantum-chemical calculations based on plane-wave density-functional-theory (DFT) methods and explored the structural and electronic properties of the series tin perovskites FASnI3-x(BF4)x (x = 0, 1, 2 and 3). The impedance and X-ray photoelectron spectra indicate that the addition of tin tetrafluoroborate instead of SnI2 suppressed the trap-assisted recombination through decreasing the Sn4+ content. The efficiency of power conversion of the FASnI3-x(BF4)x device with equimolar ratio of FAI and Sn(BF4)2 improved 72 % relative to a standard FASnI3 solar cell, with good photostability under ambient air conditions.
We also employed lead free low bandgap Cu-Sb double perovskite for catalytic oxidation of Benzene via C-H bond activation. This is first report on double perovskite catalyzing Benzene oxidation.
It is expected that these works may contribute to existing knowledge of the perovskite solar cells and might provide a viable alternative for a lead-free and pseudo-halogen based perovskite materials.

並列關鍵字

Perovskites ； Solar cells ； Lead free ； pseudohalide ； superhalide ； catalysis

參考文獻

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