基于元素直接反应的大面积钙钛矿本体异质结薄膜的原位构建、光电转换机理及器件稳定性研究

By use of the structural characteristic of interpenetrating bulk heterojunction thin film, we plan to fabricate bulk heterojunction films of perovskite/inorganic and the corresponding thin film solar cell devices through a facile elemental direct reaction route. Using elemental Pb as precursor to fabricate perovskite may facilitate the investigation of the effect of PbI2 interface structures on the device stability. This fabrication does not require a spin-coating process, which is a potential solution for thin film solar cell devices with large area. More importantly, such an in situ construction of the perovskite layer as well as the bulk heterojunction solar cell devices has many advantages. For instance, the nanostructure and morphology of the perovskite layer is well controlled with high crystallinity, so that the reproducibility of the device would be significantly improved. Secondly, the in situ formed Ag2S or CuI films can act as the transportation layers for electron or holes, respectively. Thirdly, the room temperature synthesis shows dramatic advantages for environments, cost-reduction and energy saving. Moreover, the use of narrow band-gap materials such as Ag2S may increase the absorption response of the solar cell device in the near IR region.. Taking into account of the materials fabrication, cost, spectra response, power conversion efficiencies, energy-saving and environment, the applicants will apply the surface photovoltage (SPV) and Kelvin probe and other techniques, to thoroughly study the relationships between the perovskite composition tuning, the material selection for the electron (or hole) transportation layer (requires the alignment of the band structures), the micro-interface modulation for the heterojunctions and the film deposition methods, with the charge separation, transportation, recombination, the minority charge carrier lifetime (diffusion length), as well as the device stability. Based on these studies, we aim to develop a rational fabrication route for perovskite-based bulk heterojunction thin film and the corresponding solar cell device models.

本课题旨在结合纳米互穿网络本体异质结薄膜的构造特点，采用我们成功开发的元素直接反应方法，以单质铅为前驱体，大面积原位构建基于钙钛矿结构的本体异质结薄膜太阳能电池器件，并显著提高器件重复性及稳定性。这种全新的钙钛矿制备方法无需旋涂过程，钙钛矿层结晶性好，能有效解决大尺寸器件制作问题，并有利于研究PbI2界面结构对器件稳定性的影响。室温原位生长的Ag2S、CuI等作为电子或空穴传输层，既降低成本、节能环保，又可扩展器件对近红外光谱的响应。从材料制备、光谱响应、转换效率、稳定性等因素综合考虑，运用表面光电压（SPV）及Kelvin探针等技术，分析光生载流子的传输、复合及少数载流子寿命，深入研究原位制备钙钛矿组分调控、电子或空穴传输层的选择（能带调控及能级匹配）、异质结微界面调控及成膜方式的选择等与电池器件效率及稳定性之间的关系，建立基于元素直接反应的钙钛矿本体异质结薄膜太阳能电池器件模型。

课题组圆满完成了计划书中拟定的研究任务及研究目标。基于金属表面元素直接反应方法，在低温（室温）条件下，以Pb、Cu-Pb、Bi、Cu、Ag、Cu-Bi、Cu-Ag等金属单质或合金薄膜作为前驱体，在ITO/FTO基底上原位制备了14种结晶性好、化学稳定性高、生长可控的大尺寸钙钛矿/类钙钛矿薄膜材料；获得了CH3NH3PbI3 (器件有效面积>1.0 cm2)、CH3NH3Pb(I1-xClx)3、(CH3NH3)1-xCuxPbI3、CH3NH3PbI3：AgI(QDs)、CsPbBr3等钙钛矿薄膜，以及CuBiI4、CuxAg(1-x)BiI4、Cs3Bi2I9、(CH3NH3)3Bi2l9、CuxAg1-xI等无机非铅“类钙钛矿”薄膜原位制备及电池器件性能提升的关键参数；利用瞬态表面光电压（TSPV）等技术，深入研究了ITO（FTO）/钙钛矿/空穴传输层以及 ITO/Ag2S等界面（费米能级）调控对光生载流子分离、传输及复合行为的改善及其对光电性能的提升。原位铜掺杂既可以实现钙钛矿薄膜与ITO费米能级位置的匹配，又省去了Spiro-OMeTAD等高电阻的有机层，更加有利于空穴传输，获得的大尺寸(CH3NH3)1-xCuxPbI3无空穴传输层太阳能电池PCE达到15.84%；基于CH3NH3PbI3：AgI(QDs)本体异质结PCE进一步提升至16.41%，而对应钙钛矿光伏器件的基础PCE仅为6.44%。另外，基于Cu-Pb 复合物薄膜前驱体原位制备了具有超高结晶度和（110）晶面取向以及良好稳定性的 (CH3NH3)1-xCuxPbI3 薄膜。其XRD(110)晶面衍射峰强度是见诸报道钙钛矿薄膜中最强的，比其他钙钛矿薄膜高100倍左右，为高质量金属掺杂钙钛矿薄膜的制备提供了一种全新的思路。国际上首次在室温无溶剂条件下原位合成了带隙为1.8电子伏特的新型CuBiI4-类钙钛矿薄膜，并深入研究了其本体异质结结构、光生载流子动力学与光电性能之间的关系，并实现了室温条件下的大规模可控制备。.共发表相关研究论文23篇（基金标注），其中一篇发表在《中国科学-材料》杂志（第一标注），新申请及授权国家发明专利共12件，培养博士研究生1人，硕士研究生11人，本科生8人，承办各类学术会议7次，课题组成员参加相关学术会议19次。主持人作为第一完成人获得与本课题相关省科技进步奖一等奖1项