【作者】 王伟；

【导师】 李品将； 董帅；

【作者基本信息】 河南大学 ， 电子信息（专业学位）， 2023， 硕士

【摘要】 经过多年来的发展,有机-无机杂化钙钛矿作为吸光层的太阳能电池的光电转换效率已经达到了25.7%,但钙钛矿中的有机成分在高温下易挥发、容易与氧气发生反应、还会受到紫外线的影响,这些都阻碍了其商业发展的进程。通过铯离子（Cs⁺）取代有机离子（MA⁺）制备成的全无机CsPbBr₃钙钛矿太阳能电池（PSCs）具有制造简单和良好稳定性的优点而受到关注,但CsPbBr₃钙钛矿材料晶体缺陷和离子的非辐射复合现象会导致电池的光电转换效率（PCE）较低。在光照条件下,PSCs的内建电场将光激子提取之后分离,然而相对较小的内建电场无法提供足够的强度将光生激子完全分离并使电荷从深能级缺陷态逃脱,所以增强电池的内建电场以促进电子和空穴的分离和传输是实现高效率CsPbBr₃PSCs的有效办法。为此,本论文的研究主要是通过在电子传输材料Ti O₂和CsPbBr₃之间加入超薄铁电氧化物PbTiO₃层,使其极化后产生的额外电场来增强电池的内建电场、抑制电池内载流子之间的非辐射复合、提高载流子的分离效率,从而提高电池的开路电压(V_oc)和短路电流(J_sc)。随后通过锶（Sr）掺杂PbTiO₃进一步改善Ti O₂/PbTiO₃层的费米能级和电荷传输特性,因为Sr可以增加PbTiO₃的电导率和熔点,同时还可以提高PbTiO₃薄膜的耐久性、稳定性以及晶体的相变温度和结构,最终达到改善CsPbBr₃PSCs光电性能的目的。具体的研究内容如下:（1）铁电PbTiO₃层改善CsPbBr₃PSCs性能的研究:通过乙酸铅溶液（Pb C₄H₆O₄）在450°C环境中与致密二氧化钛（Ti O₂）薄膜的Ti源原位反应生长出四方相铁电PbTiO₃薄膜,然后利用多步旋涂法制备了具有FTO/Ti O₂/PbTiO₃/CsPbBr₃/C结构的全无机CsPbBr₃PSCs。各项光电性能测试表明,在具有薄铁电PbTiO₃层的器件中,载流子的传输特性得到了改善,电池的开路电压(V_oc)和短路电流(J_sc)都更为优越,V_oc从Ti O₂器件的1.42V增加到Ti O₂/0.02MPT器件的1.48 V,J_sc从7.01 m A/cm²增加到7.50 m A/cm²,PCE从7.70%增加到9.05%,增幅比率约为17%。通过UPS和Mott-Schottky对电池能带结构和内置电场的分析,由于铁电PbTiO₃层的掺入,CsPbBr₃ PSCs的能带结构在极化电场的影响下发生改变,使得CsPbBr₃吸光层和电子层的费米能级差变大,电池的内置电场获得了增强,抑制了载流子之间的非辐射复合,从而提高了电池器件的光电性能。（2）Sr掺杂PbTiO₃薄膜对CsPbBr₃ PSCs的影响:在PbTiO₃薄膜改善CsPbBr₃PSCs性能的研究工作基础下,选取获得最佳性能的0.02M PT器件,向其前驱体溶液中加入不同含量的乙酸锶（（C₂H₃O₂）₂Sr）,在高温下与Ti O₂层表面反应形成Pb-Sr Ti O₃薄膜。通过XPS和EDS证实了Sr成功掺杂进PbTiO₃薄膜之中。通过对Ti O₂/Pb-Sr（5%）Ti O₃的UPS测试表明,少量的Sr再次减小了Ti O₂/PbTiO₃层的功函数、扩大了吸光层和电子层费米能级差,进而可以进一步提高CsPbBr₃ PSCs器件的V_oc。对电池器件进行J-V测试发现,在Sr的含量为Pb的5%时,电池的V_oc和PCE在0.02M PT器件的基础上提升到了1.50 V和9.25%,但当Sr的浓度继续增加时,PbTiO₃薄膜质量和铁电性受到影响,进而导致电池的J_sc和PCE下降,PL和TSPV等光电测试显示的载流子分离和传输能力也和J-V的规律一致。更多还原

【Abstract】 In the past decade,the photoelectric conversion efficiency of organic-inorganic hybrid perovskite as a solar cell with light absorption layer has reached 25.7%.However,the organic components in perovskite are prone to volatilization at high temperatures,susceptible to oxidation by oxygen,and also influenced by ultraviolet radiation,which have hindered the process of commercial development.All inorganic CsPbBr₃perovskite solar cells（PSCs）,which are prepared by cesium ion（Cs⁺）replacing organic ion（MA⁺）,have attracted attention because of easy preparation and good stability.Nevertheless,crystal defects of CsPbBr₃perovskite materials and non-radiative recombination of carriers lead to low power conversion efficiency（PCE）of the cells.Furthermore,the relatively small built electric field cannot provide enough intensity to completely separate the photoexcitons and make the charge escape from the deep-level defect state.Therefore,enhancing the intensity of built-in electric field of the cell to promote the separation and transmission of electrons and holes is an effective way to achieve high efficiency of CsPbBr₃ PSCs.In this paper,the study mainly aims to enhance the built-in electric field of the cells,inhibit the non-radiative recombination between the carriers,and improve the carrier separation efficiency by inducing an ultra-thin ferroelectric oxide PbTiO₃layer between the electron transport material Ti O₂ and CsPbBr₃,which could generate additional electric field after polarization to increase the open circuit voltage(V_oc)and short circuit current(J_sc)of the cells.Subsequently,the Fermi level and charge transport characteristics of Ti O₂/PbTiO₃ layer had been investigated by doping PbTiO₃ thin film with strontium（Sr）,which could increase the conductivity and melting point of PbTiO₃,and also improve the durability and stability of the PbTiO₃ film,as well as the crystal phase transition temperature and structure,and finally achieve the purpose of improving the photoelectric performance of CsPbBr₃ PSCsThe specific research contents are as follows:（1）Improvement of the performance of CsPbBr₃ PSCsby ferroelectric PbTiO₃ layer:ferroelectric PbTiO₃ thin films were grown by in-situ reaction of lead acetate solution（Pb C₄H₆O₄）with the Ti source of titanium dioxide（Ti O₂）dense films at 450°C.Then using multi-step spin coating method for the preparation of the FTO/Ti O₂/PbTiO₃/CsPbBr₃/C structure of the inorganic CsPbBr₃ PSCs,the photoelectric performance tests show that the transmission properties of carrier have been improved in the ferroelectric PbTiO₃ thin layer device.and of the cell are better.The open circuit voltage(V_oc)had been increased from 1.42 V of Ti O₂devices to 1.48 V of Ti O₂/0.02M-PT devices,the short circuit current(J_sc)had been increased from 7.01m A/cm² to 7.50 m A/cm²,and PCE had been increased from 7.70%to 9.05%（The conversion efficiency of the cell had been improved about 17 percent）.UPS and Mott-Schottky were used to analyze the energy band structure and internal electric field of the cell.It was found that the energy band structure of CsPbBr₃ PSCscould be changed under the influence of polarization electric field due to the incorporation of ferroelectric PbTiO₃ layer,which enlarged the Fermi energy level difference between the absorptive layer and the electron layer of CsPbBr₃ and enhanced the internal electric field of the cell.The result indicated that the non-radiative recombination between carriers have been inhibited and the photoelectric performance of the cell device have been improved.（2）Effect of Sr-doped PbTiO₃thin film on CsPbBr₃ PSCscells:Based on the research of PbTiO₃ thin film improving the performance of CsPbBr₃ PSCs,0.02M PT device with the best performance was selected,and strontium acetate(（C₂H₃O₂）₂Sr with different contents was added to its precursor solution to react with the surface of Ti O₂ layer at high temperature to form Pb-Sr Ti O₃ thin film.The successful doping of Sr into PbTiO₃ thin films was confirmed by XPS and EDS.The UPS test of Ti O₂/Pb-Sr（5%）Ti O₃ showed that a small amount of Sr again reduced the work function of Ti O₂/PbTiO₃ layer and expanded the Fermi energy level difference between the light-absorbing layer and the electron layer,which could further improve the V_oc of CsPbBr₃ PSCsdevices.The J-V test on the cell device shows that when the content of Sr is 5%of Pb,the V_oc and PCE of the cell increase to 1.50 V and 9.25%on the basis of 0.02M PT device.However,when the concentration of Sr continues to increase,the quality and ferroelectricity of PbTiO₃ film are affected.As a result,the J_scand PCE of the cell are decreased,and the carrier separation and transmission capability shown by PL and TSPV are also consistent with the law of J-V.更多还原