【作者】 王浩然；

【导师】 段羽；

【作者基本信息】 吉林大学 ， 微电子学与固体电子学， 2020， 博士

【摘要】 原子层沉积是一种基于气相前驱体与衬底表面基团间化学反应的薄膜制备技术,其前驱体交替通入的生长方式使得产物以原子级别的厚度被逐层化学吸附在衬底上。原子层沉积制备的薄膜因此具有致密无针孔、保型性高、厚度高度可控、成分高度可控等优点。近年来,原子层沉积制备的封装薄膜成为解决钙钛矿太阳能电池在空气中稳定性问题的重要方法之一。然而,金属卤化物钙钛矿结构的热解温度和化学稳定性极低,封装钙钛矿太阳能电池过程中过高的温度或活性前驱体的使用会导致器件损伤,使性能大幅下降。所以在低温下通过原子层沉积制备高性能封装薄膜至关重要。本文主要围绕基于低温原子层沉积的钙钛矿太阳能电池薄膜封装展开研究,从低温原子层沉积中的反应机制和位阻效应着手,提高制备薄膜的封装性能。最后,在高质量低温原子层沉积薄膜的基础上,针对钙钛矿太阳能电池设计了独特的无损封装结构,首次将等离子增强原子层沉积应用于钙钛矿电池的薄膜封装,成功的解决了钙钛矿电池的高性能封装薄膜制备问题,未来有望大幅提高钙钛矿光伏器件在空气中的稳定性。本论文的主要研究内容和成果概括如下:1、基于原位四极杆质谱仪测试与分析,总结低温下三甲基铝和活性前驱体（氧气等离子体和臭氧）的反应机制,确定一种三甲基铝和氧气等离子反应时氧原子嵌入碳氢键之间的反应路径,认为反应路径的区别是造成薄膜性能差异的主要原因。2、使用原位石英晶体天平表征原子层沉积的自限制特性。具体为使用每循环质量增加的标准差系数表示每循环生长量的离散程度,从而表征自限制生长的稳定性。并据此研究原子层沉积自限制特性与生长的薄膜性能之间的关系。3、研究低温原子层沉积中分子动力学对表面吸附的影响,通过控制脉冲方式、脉冲时间和清洗时间控制前驱体分压和暴露时间,进而研究分子运动对暂态空间位阻、饱和吸附和物理吸附的影响。使用多步短脉冲法在大幅提高低温原子层沉积薄膜密度的同时降低了一半吸附平衡所需的吹扫时间。4、使用低活性前驱体乙二醇无损伤封装钙钛矿电池,并作为等离子增强原子层沉积封装过程中的保护层。低温分子层沉积的薄膜中残留着未反应基团消耗穿透薄膜的活性等离子,避免对电池器件的损伤。分子层沉积/等离子增强原子层沉积复合结构的水汽透过率高达1.3×10^-5g/m²/day,封装后器件保持最初效率的99.91%,实现钙钛矿电池的高性能无损伤封装。更多还原

【Abstract】 Atomic layer deposition is a thin film fabricationtechnology based on chemical reactions between gas-phase precursors and groups on the surface of substrates.The precursors are dosed in an alternating manner so that the product is chemically adsorbed on the substrates layer by layer at the atomic level.The films prepared by atomic layer deposition,therefore,have the advantages of being dense,pinhole-free,conformal,highly controllable in thickness and components.In recent years,encapsulation films prepared by atomic layer deposition have become one of the important methods to solve the problem of stability of perovskite solar cells.However,the metal halide perovskite structure shows extremely low pyrolysis temperature and chemical stability.Excessive temperatures or the use of active precursors in the encapsulation process of perovskite solar cells usually cause damage,which significantly reduces device performance.This paper mainly focuses on the research of perovskite solar cell thin-film encapsulation based on low-temperature atomic layer deposition.It starts from the reaction mechanism and steric effect in low-temperature atomic layer deposition to improve the films’barrier performance.Finally,based on the preparation of high-quality low-temperature films,a new encapsulation structure is designed for metal halide perovskite solar cells with inferior stability.Plasma-enhanced atomic layer deposition consequently is applied for the first time in thin-film encapsulation of perovskite solar cells.This novel strategy successfully solved the problem of preparing high-performance encapsulation films for perovskite solar cells,and it is expected to significantly improve the stability of perovskite solar cells in the future.The research contents and results of this thesis mainly include the following aspects:1、Based on the in-situ quadrupole mass spectrometer monitoring,the reaction paths of trimethylaluminum and active precursors（oxygen plasma and ozone）at low temperature are summarized,and a reaction path between trimethylaluminum and oxygen plasma that oxygen atomics inserted into the carbon-hydrogen bonds is determined.It is believed that the difference in reaction paths is the main reason for the difference in film properties.2、In-situ quartz crystal balances were used to characterize the self-limiting properties of atomic layer deposition.Correctly,the standard deviation coefficient of the mass increase per cycle is used to represent the degree of dispersion of the growth amount per cycle,thus characterizing the stability of self-limiting growth.Based on this,the relationship between the self-limiting characteristic of atomic layer deposition and the properties of the grown thin films was studied.3、Investigate the effects of low kinetic on film properties in low-temperature atomic layer deposition.By controlling the pulse mode,pulse time and purge time to control the precursor partial pressure and exposure time,the effects of molecular motion on transient steric hindrance,saturation adsorption and physical adsorption were studied.It was found that the multiple short pulse method significantly reduces the low-temperature atomic layer deposition film density while reducing half of the purge time required for the adsorption equilibrium.4、Perovskite solar cells were encapsulated without damage using low-activity precursor ethylene glycol.It also acted as a protective layer in the plasma-enhanced atomic layer deposition encapsulation process.Unreacted groups remained in the film fabricated by the low-temperature molecular layer deposition,which consumed active plasma that penetrates the film,thereby avoiding damage to the solar cells.The molecular layer deposition/plasma-enhanced atomic layer deposition composite structure shown a water vapor transmission rate as high as 1.3×10^-5g/m²/day.After encapsulation,the devices maintained 99.91%of the original efficiency,achieving high-performance and non-damaging encapsulation of the perovskite solar cells.更多还原