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杂化钙钛矿[(CH3)2NH2]3[BiI6]的合成、表征及性能研究
赵赫
学位类型硕士
导师王传义
2017-05-28
学位授予单位中国科学院大学
学位授予地点北京
学位专业材料物理与化学
关键词[(Ch3)2nh2]3[Bii6] 无铅 太阳能电池 1d 光催化
摘要

有机无机杂化材料是由无机骨架和有机半部组成的一类材料,兼具无机半部的可控电子性能、优异电子传输性能、稳定性以及有机组分低生产成本、结构多样性的双重优点,因此有机无机杂化材料在催化、传感器、药物传输系统发光器件以及太阳能电池领域具有广泛的研究和潜在的应用前景。有机无机杂化材料,特别是钙钛矿体系,短时间内在太阳能电池领域取得了巨大的进步。特别是以CH3NH3PbI3为代表的钙钛矿光吸收层材料,在太阳能转化效率方面取得了惊人的成绩;由于其低的载流子复合、低的缺陷态密度、高的吸收系数和优异的电子传输性能,其太阳能转化效率由最初的3.8%飙升至22.1%。再者,鉴于钙钛矿太阳能电池低的生产成本和高的能量转化效,从而使其成为第三代太阳能电池中具有代表性的高性能太阳能电池。然而,铅元素的毒性以及CH3NH3PbI3类钙钛矿的本征不稳定性,限制了其大规模开发和商业化步伐。在本论文中,以无毒的铋元素代替铅元素,制备了有机无机杂化铋基单晶[(CH3)2NH2]3[BiI6]。以该材料为基础,研究了其作为太阳能电池光活性层、晶体形貌演化过程以及作为均相光催化剂分解HI制备氢气的性能,在太阳能电池、催化领域具有研究价值。具体总结如下:(1)本章工作中,首次以溶剂热的方法制备了[(CH3)2NH2]3[BiI6]单晶,单晶尺寸达到毫米级别,且晶体纯度高。进而系统的研究了[(CH3)2NH2]3[BiI6]的光电性能。实验表明[(CH3)2NH2]3[BiI6]具有本征稳定性,就有较高的热稳定性、光稳定性和空气稳定性。通过能级分析,选择二氧化钛作为电子传输层,首次将[(CH3)2NH2]3[BiI6]作为光活性层,组建了太阳能电池器件,所得电池性能为开路电压0.58 V,短路电流0.12 mA cm-2,填充因子31.76%,电池转化效率0.025%。这为设计无铅、高稳定性的有机无机杂化材料作为光活性层提供一种新思路。(2)本章工作中,针对于第一部分制备出不同形貌的[(CH3)2NH2]3[BiI6]晶体,研究了晶体由六边形到纤维状的机理和演变过程。实验发现,碘化甲胺的存在能够提高晶体的结晶性和尺寸,其机理可能是碘离子增加体系的结晶度,甲胺离子提高晶体的尺寸。由六边形到纤维状的演化是甲胺阳离子和甲酸共同作用的结果,即甲酸促进晶体以垂直于六边形面的方向生长,而甲胺阳离子使晶体的尺寸增加,两者共同作用下,使六边形晶体演化为纤维状晶体。进一步通过光学显微镜观察了晶体由六边形到纤维状演变过程。再者,通过时间分辨荧光光谱,发现纤维状晶体具有更高的荧光寿命(1.95 ns)。这为可控合成不同形貌晶体提供一种新思路,同时此方法可以拓展到在太阳能电池电子传输层上,原位生长有机无机杂化材料。(3)本章工作中,利用简单的溶液法合成了[(CH3)2NH2]3[BiI6]晶体,通过XRD分析表明,此方法和溶剂热方法所得材料为同一物质;同时,此方法较第一章中的溶剂热方法更加简单和快捷。再者,以[(CH3)2NH2]3[BiI6]作为均相催化剂,研究了其光催化分解HI制备氢气的活性,而均相的CH3NH3PbI3无分解HI产氢性能。在此基础上,通过引入共催化剂铂,很大程度提高了其产氢性能,提高了其在550 nm到900 nm范围的吸收。研究发现,引入的铂离子并未还原为铂单质,而是以四价铂和二价铂离子的形式存在。最后,长期稳定性实验表明,该材料具有长期产氢稳定性。

其他摘要

Organic-inorganic hybrid material, constituted by the inorganic framework and the organic component, are widely researched considering the superb properties, such as the controllable electronic properties, high electron transfer, high stability as well as the low processing cost. Thus it attracts numerous focus on these hybrid material, showing significant research value and application potentiality in catalysis, sensors, drug delivery system, luminescent devices and solar cells. The hybrid organic-inorganic materials, particular the perovskite family, have achieved astounding progress in solar cells in a short time span. The typical CH3NH3PbI3 perovskites have exhibited a surge of the efficiencies from 3.8% to 22.1%. Perovskite solar cells based on CH3NH3PbI3 have exhibited a potential to supplant the silicon-based solar cells in view of the impressive efficiency-to-cost ratio. However, despite the spectacular success respect to the efficiencies, the toxicity and instability issues of lead-based perovskites still severely plague their application, which are the adverse factors to the public acceptance and commercial viable implementation. In this thesis, a lead-free organic-inorganic hybrid material, namely [(CH3)2NH2]3[BiI6], were synthesized to address the toxicity and stability issues upon the CH3NH3PbI3. Based on this material, we systematically investigated its physicochemical and optoelectronic properties as well as its growth and the course of the evolution from hexagonal to fibrous. We also focus on its potential application in solar cells and photo catalysis as a lead-free alternative of CH3NH3PbI3. Specifically, this dissertation covers the following three parts:(1) A dimethylammonium-based semiconductor [(CH3)2NH2]3[BiI6] was synthesized via a solvothermal route, in which the product of dimethylamine derived from the decomposition of N, N-dimethylformamide (DMF) under solvothermal atmosphere acts as the organic moiety after protonation. The physicochemical and optoelectronic properties as well as the stability of the material were studied in detail. We find that the synthesized [(CH3)2NH2]3[BiI6] exhibits a fluorescence lifetime of 1.95 ns, which demonstrates that it is a potential material for solar cell applications. It is interesting to note that the as-synthesized material shows long-term stability upon exposure to air and sunlight for four weeks, as well as better intrinsic thermal stability. The as-synthesized [(CH3)2NH2]3[BiI6] is used as the light-harvesting active layer to assemble a photovoltaic device for the first time and the photovoltaic parameters are determined as Jsc = 0.12 mA cm?2, Voc = 0.58 V, FF = 31.76%, and PCE = 0.025%, respectively, suggesting the [(CH3)2NH2]3[BiI6] is a promising candidate to address the issues related to toxicity and instability of lead-based perovskites. (2) Due to the excellent carrier transfer property, wire-based hybrid materials show higher optoelectronic property. The evolution about the crystal morphology of [(CH3)2NH2]3[BiI6] from hexagonal to fibrous are investigated. We find that the existence of CH3NH3I can improve the crystallinity as well as the crystal size, which are originated from the effect of I- and CH3NH3+. The evolution from the hexagonal to fibrous are the synergic effect of formic acid and CH3NH3I, which are confirmed by the fact that the introduction of N- methylformamide can induce this evolution. In addition, the evolution is studied via in situ optical microscopy. Time-resloved photoluminence spectra show that the fibrous crystals of [(CH3)2NH2]3[BiI6] obtain a higher average lifetime than that of hexagonal one. This work can hold a promise to synthesize crystal material with controllable morphology, and a potential to be applied in solar cells.(3) Using a simple and efficient solvent method, the same product of [(CH3)2NH2]3[BiI6] are obtained. This material can form a homogeneous solution with a catalytic property upon the dissociation of HI with the aid of solar. We develop an organic-inorganic hybrid Pt/[(CH3)2NH2]3[BiI6] as homogeneous photocatalyst for harvesting the full spectrum of visible light and demonstrate its highly efficient for hydrogen production from hydriodic acid splitting. Under irradiation at 465 nm, the photocatalytic system achieves apparent quantum yield of ~82.8% for photocatalytic hydrogen production along with a stable activity for at least 100 hours. The Pt ions (Pt2+ and Pt4+) are the active species rather than the Pt (0) in this case. Our findings indicate that the introduction of Pt can not only improve the photocatalytic activity but also increase the light absorption of the photocatalyst from 550 nm to 900 nm, which opens an approach for designing and fabricating organic-inorganic semiconductors with improved performance in photocatalysis and optoelectronic devices.

文献类型学位论文
条目标识符http://ir.xjipc.cas.cn/handle/365002/4981
专题环境科学与技术研究室
作者单位中国科学院新疆理化技术研究所
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赵赫. 杂化钙钛矿[(CH3)2NH2]3[BiI6]的合成、表征及性能研究[D]. 北京. 中国科学院大学,2017.
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