【作者】 李娜；

【导师】 陈岗；

【作者基本信息】 吉林大学 ， 凝聚态物理， 2022， 博士

【摘要】 当前社会面临的首要任务是开发和利用可再生能源以解决能源与环境问题,这也是实现经济社会可持续发展的关键之处。太阳能作为广泛应用的清洁能源之一,能够极大程度缓解能源紧缺现况,改变现有的以煤、石油、天然气为主的能源消费体系,实现能源替换。光伏器件是太阳能开发及应用的重要手段,可以高效的将光能转换为可用于生产生活的电能,确保人类生活质量,积极推动太阳能大规模发展。钙钛矿太阳能电池因具有较宽的光谱响应、优良的光电性能及可调的晶体结构等独特的优势在光伏器件中脱颖而出。自2009年钙钛矿太阳能电池的神秘面纱被揭开以后,器件的光电转换效率一路飙升,展现出惊人的应用前景,钙钛矿太阳能电池也被认为是最具潜能的新型可再生能源电池。尽管钙钛矿太阳能电池近年来发展迅猛,但要向商业化迈进仍然面临许多挑战,比如器件对湿度和温度的耐受性、各功能层性能、光电转换效率、制作成本及毒性等问题。空穴传输层是钙钛矿太阳能电池的重要组分之一,可用于定向转运吸光层内产生的空穴,使其可以高效的被外侧电极收集,减少界面处因光生载流子复合而造成的能量损失,对电池性能的提升起到至关重要的作用。叶绿素作为自然界不可或缺的天然色素,在光合作用中充当关键角色,其功效主要表现在对太阳光的高效捕获以及实现电荷的分离和转移。此外,绿色材料叶绿素还具有资源丰富、结构简单、易于调控等特点,这些性质均有利于该材料在钙钛矿太阳能电池中发挥出出色的电荷抽取及转移能力,从而制备出高效率的钙钛矿光伏器件。鉴于此,本文通过对天然色素叶绿素进行分子工程,合成一系列叶绿素衍生物,将其用作钙钛矿太阳能电池中的空穴传输层,以此设计出性能优良的光伏器件。首先,以天然细菌叶绿素-a为原材料,我们合成五种在C17位具有不同取代基的细菌叶绿素衍生物BChls-1~5,将其作为空穴传输材料用于基于CH3NH3Pb I3的钙钛矿太阳能电池中。连有不同酯化基团的BChls-1~5可通过简单旋涂制备出表面形貌各异的聚集体薄膜,并展现出各不相同的电荷抽取以及转移能力。其中,基于十二烷基的BChl-2可为器件内部的电荷转移提供最有效的运输路径以及最佳的界面环境,实现了13.6%的器件光电转换效率。该工作助力于开发低廉环保有效的绿色材料,为光伏领域的可持续发展提供思路与途径。为进一步挖掘叶绿素小分子在光伏器件中的应用潜力,我们设计出与BChls-1~5结构相似的含锌叶绿素衍生物Zn Chls-1~4,其结构中的中心金属、C3l位的羟基以及C13位的羰基可以产生较强的分子间相互作用,促进叶绿素分子自组装形成J-聚集,这种高度有序的结构有利于载流子的运输。此外,Zn Chls-1~4在C17位连有不同长度且不直接与叶绿素π系统共轭的烃链,这种结构差异不影响Zn Chls-1~4单体的电子吸收光谱和能级,但会使其聚集体薄膜呈现出不同的光物理化学性质,这主要体现在基于不同材料的钙钛矿太阳能电池的性能差距。使用Zn Chls-2,3作空穴传输层的器件实现最优的光伏性能,这可归因于Zn Chls-2,3较低的HOMO能级以及电池内部最有效的电荷传输,此外,长链烃基的存在提高了Zn Chls-2,3的溶解度,使其形成表面光滑的聚集体薄膜,这对器件性能也有积极影响。在之前的工作中,我们一直致力于开发和应用单层叶绿素衍生物,探究其分子结构对器件性能的影响。但伴随着研究的深入,单层传输层在结构及功能上的不足之处也逐渐暴露,其薄膜形态及在空穴传输等方面的表现不尽如人意。由此我们尝试使用两种叶绿素衍生物(Zn Chl-1和H2Chl)将其用作平面钙钛矿太阳能电池的双层空穴传输层,制备出结构为ITO/Sn O2/MAPb I3/Zn Chl-1/H2Chl/Ag的电池,旨在结合两种材料的性能优势以提升器件效率。虽然H2Chl因过低的HOMO能级对空穴的层间传输起到阻碍作用,导致基于双层结构的器件的Jsc下降,但双层空穴传输层依然展现出其特有优势,在界面处能够有效的抑制载流子复合,减少光生载流子的损失,进而实现最高14.1%的光电转换效率,并获得良好稳定性。随后,考虑到H2Chl分子不匹配的能级分布及较差的空穴传输能力,我们在双层结构中引入具有优异光电性能的并五苯小分子替换掉H2Chl,制备出基于叶绿素的双层有机空穴传输层(并五苯/Zn Chl-1),并将其用在钙钛矿太阳能电池中,以进一步验证基于叶绿素的双层空穴传输层在光伏器件中的可能性。其中,并五苯和Zn Chl-1可通过不同的成膜方式分别制得排列有序的晶体薄膜和聚集体薄膜,这意味着载流子可在其内部高效运输,使得基于单层并五苯和单层Zn Chl-1的器件分别获得9.25%和11.5%的效率,而双层有机传输层完美复刻了双层叶绿素衍生物抑制电荷重组的功效,降低界面处的能量损失,最终得到了最高的填充因子和光电转换效率。以上关于叶绿素型空穴传输层的研究既符合绿色经济的发展需求,又使我们对天然材料叶绿素在光伏器件中的应用潜能有了更加深入的了解和认识,有利于实现可再生清洁能源的高效利用。更多还原

【Abstract】 The primary task facing the current society is to develop and utilize renewable energy to solve energy and environmental issues,which is also the key to achieving sustainable development of economic social.As one of the widely used clean energy sources,solar energy can greatly alleviate the current situation of energy shortage,change the existing energy consumption system dominated by coal,oil and natural gas,and then realize energy replacement.Photovoltaic devices are an important method of solar energy development and application,which can efficiently convert light energy into electrical energy that can be used for production and life,ensure the quality of human life,and actively promote the large-scale development of solar energy.Perovskite solar cells stand out among photovoltaic devices due to their unique advantages such as wide spectral response,excellent photoelectric properties,and tunable crystal structure.Since the mystery veil of perovskite solar cells(PSCs)was uncovered in 2009,the power conversion efficiency(PCE)of devices has been soaring,showing amazing application prospects,PSCs are regarded as the most potential new renewable energy cells.Despite the rapid development of PSCs in recent years,there are still many challenges ahead for commercialization,such as the tolerance of devices to humidity and temperature,the performance of each functional layer,PCE,fabrication cost,and toxicity.The hole transport layer(HTL)is one of the important components of PSCs.It can be used to directionally transport the holes generated in the light absorption layer,so that they can be efficiently collected by the outer electrodes,reduces the energy loss caused by the recombination of photogenerated carriers at the interface,and plays a crucial role in improving the performance of cells.Chlorophylls,as indispensable natural pigments in nature,act a key role in photosynthesis.Their efficacy is mainly reflected in the efficient capture of sunlight and the separation and transfer of charges.Besides,the green material chlorophylls also have the characteristics of rich resources,simple structure and easy regulation.These properties are conducive to their excellent charge extraction and transfer capabilities in PSCs,thereby preparing high-efficiency perovskite photovoltaic devices.In view of this,in this paper,a series of chlorophyll derivatives are synthesized by molecular engineering of natural pigment chlorophylls,and are used as HTLs in PSCs,so as to design photovoltaic devices with excellent performance.First,using natural bacteriochlorophyll-a as raw material,we synthesized five bacteriochlorophyll derivatives BChls-1~5 with different substituents at C17 position,and used them as hole transport materials(HTMs)for CH3NH3 Pb I3-based PSCs.BChls-1~5 with various esterifying groups can form aggregate films with different surface morphologies through simple spin coating,and exhibit distinct charge extraction and transfer capabilities.Among them,dodecyl-based BChl-2 can provide the most efficient transport path and the best interface environment for charge transfer inside the device,achieving a PCE of 13.6%.This work contributes to the development of low-cost,environmentally friendly,effective green materials,and provides ideas and ways for sustainable development in photovoltaic field.In order to further explore the application potential of chlorophyll molecules in photovoltaic devices,we designed zinc-chlorophyll derivatives Zn Chls-1~4,which are similar in structure to BChls-1~5.The central zinc ion,31-hydroxy group,and 131-carbonyl group in their structure can produce strong intermolecular interaction and promote the self-assembly of chlorophyll molecules to form J-aggregation.This highly ordered structure is beneficial to the transport of carriers.In addition,Zn Chls-1~4 have hydrocarbon chains with different lengths at the C17 position that are not directly conjugated with the chlorophyll π system.This structural difference does not affect the electronic absorption spectra and energy levels of Zn Chls-1~4 monomers,but will make their aggregate films exhibit various photophysical and chemical properties,which are mainly reflected in the performance disparity of PSCs based on different materials.The devices using Zn Chls-2,3 as HTLs achieve the best photovoltaic performance,which can be attributed to the lower HOMO energy levels of Zn Chls-2,3 and the most efficient charge transport in PSCs.Besides,the existence of long-chain hydrocarbon groups improves the solubility of Zn Chls-2,3,thus forming aggregate films with smooth surfaces,which also have positive effects on device performance.In the previous work,we have been committed to developing and applying monolayer chlorophyll derivatives and investigating the impact of their molecular structure on device performance.However,with the in-depth research,the deficiencies of monolayer transport layer in structure and function are gradually exposed,and its film morphology and hole transport performance are not satisfactory.Therefore,we tried to use two chlorophyll derivatives(Zn Chl-1 and H2Chl)as bilayer HTL for planar PSCs,and prepared cells with ITO/Sn O2/MAPb I3/Zn Chl-1/H2Chl/Ag structure,aiming to improve devices efficiency by combining the performance merits of these two materials.Although H2 Chl hinders the interlayer transport of holes due to its too low HOMO energy level,resulting in a decrease in Jsc of the device based on bilayer structure,the bilayer HTL still shows its unique advantages,which can effectively suppress carrier recombination at the interface and reduce the loss of photogenerated carriers,thus achieving a maximum PCE of 14.1% and obtaining good stability.Subsequently,considering the mismatched energy level distribution and poor hole transport ability of H2 Chl molecule,we introduced pentacene with excellent photoelectric properties into the bilayer structure to replace H2 Chl,prepared a chlorophyll-based bilayer organic HTL(pentacene/Zn Chl-1),and used it in PSCs to further verify the possibility of chlorophyll-based bilayer HTL in photovoltaic devices.Among them,pentacene and Zn Chl-1 can be respectively prepared into ordered crystal film and aggregate film by different film-forming methods,which means that carriers can be efficiently transported inside them.Therefore,devices based on monolayer pentacene and monolayer Zn Chl-1 can obtain the PCE of 9.25% and11.5%,respectively.While the bilayer organic transport layer perfectly replicates the effect of bilayer chlorophyll derivatives in inhibiting charge recombination and reduces the energy loss at the interface.Finally,the PSCs based on pentacene/Zn Chl-1obtained the highest fill factor(FF)and PCE.The above research on chlorophyll-type HTL not only meets the development requirements of green economy,but also enables us to have a deeper understanding and cognition of the application potential of natural material chlorophyll in photovoltaic devices,which is conducive to realizing the efficient utilization of renewable clean energy.更多还原