【作者】 李丹；

【导师】 魏茂彬；

【作者基本信息】 吉林师范大学 ， 材料物理与化学， 2023， 硕士

【摘要】 钙钛矿材料具有可调的带隙、高的吸收系数、高载流子迁移率和长载流子扩散长度等优异的光电性能,基于这种材料所制备的钙钛矿太阳电池（PSCs）,具有低成本、简单的制备工艺和出色的功率转换效率,已成为一种极具前景的光伏器件。钙钛矿吸收层和电荷传输层的结晶质量和光电性质是决定器件光伏性能的关键所在。对于钙钛矿吸收层来说,常用的液相旋涂法制备过程中,钙钛矿薄膜结晶速度极快,导致钙钛矿结晶质量低、晶粒尺寸小。伴随而来的大量晶界缺陷会成为载流子非辐射复合中心诱导电荷复合,增大器件的迟滞效应。而电子传输层的质量则直接决定着电子的提取与传输,薄膜存在针孔和光损失都限制了器件光伏性能的提升。目前,添加剂工程是提升钙钛矿吸收层和电子传输层结晶质量和光电性质、进而提升钙钛矿太阳电池光伏性能的有效手段之一。碳基材料以其结构多样、表面化学性质丰富、可调控性强、优异的电输运特性等优点成为可应用在PSCs中的一类优异添加剂。本论文选取功能化碳基材料修饰钙钛矿吸收层,研究不同功能化碳基材料对吸收层晶体结构、光电性质以及光伏性能的影响规律,揭示其对钙钛矿太阳电池光伏性能和稳定性的影响规律,并在钙钛矿层优化的基础上,在电子传输层引入下转换发光材料提高紫外光利用率,进一步提高器件的光伏性能,并阐明相关物理机制。取得的创新性成果如下:1.同时增大钙钛矿晶粒尺寸和钝化晶界缺陷是提高PSCs光伏性能的有效手段。我们将氨基功能化碳纳米管（NH₂-CNT）作为晶体生长模板和晶界钝化剂,引入到钙钛矿前驱体溶液中,调控钙钛矿膜的晶粒生长和载流子传输行为。研究结果表明,氨基可以将钙钛矿晶核固定在NH₂-CNT骨架上,得到晶粒尺寸较大的钙钛矿薄膜。NH₂-CNT主要存在于晶界,其-NH₂可以与Pb²⁺发生Lewis酸碱反应,能够有效钝化深能级缺陷,形成更快的载流子输运通道,加速电子的提取和转移。最终基于NH₂-CNT修饰的MAPbI₃基太阳电池的功率转换效率达到21.01%。2.为了在调控钙钛矿薄膜结晶质量的同时,同步提升器件环境稳定性,我们设计并利用水热法合成了F-g-C₃N₄量子点材料,并将其添加到钙钛矿薄膜中,调控钙钛矿薄膜的结晶过程以及PSCs的光伏性能和稳定性。结果表明:F-g-C₃N₄为钙钛矿的晶粒生长提供了成核位点,延缓了钙钛矿的结晶速率,增大了晶粒尺寸,降低了缺陷态密度。F-g-C₃N₄修饰后钙钛矿薄膜的价带向上移动,与Spiro-OMe TAD空穴传输层的HOMO能级更加匹配,加速了载流子的分离与提取。当F-g-C₃N₄添加浓度为0.05 wt%时,MAPbI₃基太阳电池的功率转换效率达到了21.18%,而且疏水F基团的存在提高了薄膜的湿度稳定性,器件在大气环境中稳定性也得到了提升。3.为了提高紫外光利用率,在利用F-g-C₃N₄优化钙钛矿薄膜的基础上,我们将具有下转换发光能力的EuBr₂掺到电子传输层中,优化电子传输层及界面,进一步提高PSCs的光伏性能。研究表明EuBr₂可以将不被钙钛矿薄膜吸收的紫外光转换为可被其吸收的可见光,有效提高了器件的光利用率,提高了器件的J_sc。同时,Eu²⁺氧化了界面处的零价铅（Pb⁰）缺陷,同时减少了零价碘（I⁰）缺陷,抑制了界面载流子复合。EuBr₂的存在还使得SnO₂电子传输层的导带向上偏移,与钙钛矿薄膜的导带更加匹配,加速了载流子的分离和传输。当EuBr₂添加浓度为3 mg/ml时,MAPbI₃基太阳电池的的功率转换效率提高到21.49%,并表现出良好的紫外光和湿度稳定性。综上,本论文提出了两种利用环境友好的功能化碳材料来调节钙钛矿吸收层实现高效稳定PSCs的策略,为功能化碳基材料的设计与开发提供了新思路,也为PSCs光伏性能的提升提供了后备技术方案。更多还原

【Abstract】 Perovskite materials have excellent photoelectric properties such as adjustable band gaps,high absorption coefficient,high carrier mobility,and long carrier diffusion length.Perovskite solar cells（PSCs）fabricated based on this material have become a promising photovoltaic device due to their low cost,simple fabrication process,and excellent power conversion efficiency.The crystalline quality and photoelectric properties of the perovskite absorption layer and charge transfer layer are key factors determining the photovoltaic performance of devices.For perovskite absorption layers,the crystallization speed of perovskite thin films in the commonly used liquid phase spin coating process is extremely fast,resulting in low crystal quality and small crystal size of perovskite.The accompanying large number of grain boundary defects then turns into carrier nonradiative recombination centers to induce charge recombination and increase the hysteresis effect of PSCs.The quality of the electron transport layer directly determines the extraction and transportation kinetics of electrons.But the existence of pinholes and light loss wihin it usually limit the improvement of the photovoltaic performance of the device.At present,additive engineering is one of the effective means to improve the crystalline quality and photoelectric properties of perovskite absorption and electron transport layers,thereby improving the photovoltaic performance of perovskite solar cells.Carbon-based materials have become an excellent additive for PSCs due to their diverse structures,various surface chemical properties,strong controllability,and excellent electrical transport properties.In this thesis,functionalized carbon-based materials are selected to modify the perovskite absorption layer,and their effects on the crystal structure,photoelectric properties,and photovoltaic performance are studied.The influence of these materials on the photovoltaic performance and stability of PSCs are investigated.Based on the above optimization of perovskite layer,downward conversion luminescence materials are introduced into the electron transport layer to improve the utilization of ultraviolet light,further improving the photovoltaic performance of the device,and clarifying the relevant physical mechanisms.The obtained innovative achievements are as follows:1.Increasing the grain size of perovskite and passivating grain boundary defects simultaneously are one of effective means to improve the photovoltaic performance of PSCs.We introduced amino functionalized carbon nanotubes（NH₂-CNT）as crystal growth templates and grain boundary passivators into perovskite precursor solutions to regulate the crystal growth and carrier transport behavior of perovskite films.The results show that the amino group can fix the perovskite crystal nucleus on the NH₂-CNT skeleton,and obtain perovskite thin films with larger grain sizes.NH₂-CNT mainly exists at grain boundaries,and its-NH₂ can react with Pb²⁺in a Lewis acid base reaction,effectively passivating deep level defects,forming faster carrier transport channels,and accelerating the extraction and transfer of electrons.Finally,the power conversion efficiency of MAPbI₃ based solar cells modified with NH₂-CNT reached 21.01%.2.In order to simultaneously improve the environmental stability of devices while regulating the crystalline quality of perovskite films,we designed and synthesized F-g-C₃N₄quantum dot materials by hydrothermal method,and added them to perovskite films to regulate the crystallization process of perovskite films and the photovoltaic performance and stability of PSCs.The results show that F-g-C₃N₄ provides a nucleation site for the crystal growth of perovskite,delays the crystallization rate of perovskite,increases the grain size,and reduces the density of defect states.The valence band of the F-g-C₃N₄ modified perovskite thin film moves upward,which better matches the HOMO level of the Spiro-OMe TAD hole transport layer,accelerating the separation and extraction of carriers.When the concentration of F-g-C₃N₄ was 0.05 wt%,the power conversion efficiency of MAPbI₃-based solar cells reached 21.18%.Moreover,the presence of hydrophobic F groups improved the humidity stability of the perovskite film and the stability of the device in the atmospheric environment.3.In order to improve the utilization of ultraviolet light,on the basis of optimizing perovskite films with F-g-C₃N₄,we introduced EuBr₂ with downconversion luminescent capability into the electron transport layer to optimize the electron transport layer and interface,and further improve the photovoltaic performance of PSCs.The results show that EuBr₂ can convert ultraviolet light that is not absorbed by perovskite films into visible light that can be absorbed by them,so that effectively improves the light utilization of the device and improving the J_sc.At the same time,Eu²⁺oxidizes the zero valent lead（Pb⁰）defects at the interface,while reducing the zero valent iodine（I⁰）defects,inhibiting the interfacial carrier recombination.The presence of EuBr₂ also shifts the conduction band of SnO₂ electron transport layer upward,which makes it well match with the conduction band of the perovskite film so that accelerating the charge separation and transportation.When the concentration of EuBr₂ was 3 mg/ml,the power conversion efficiency of MAPbI₃ based solar cells increased to 21.49%with exhibiting good UV and humidity stability.In summary,this thesis proposes two strategies for using environmentally friendly functionalized carbon-based materials to adjust the perovskite absorption layer to achieve efficient and stable PSCs,which not only provides new concept for the design and development of functionalized carbon-based materials,but also provides backup technique for improving the photovoltaic performance of PSCs.更多还原