【作者】 王欢；

【导师】 陈炜；

【作者基本信息】 华中科技大学 ， 光学工程， 2017， 博士

【摘要】 有机/无机杂化卤化物钙钛矿材料ABX₃（A=CH₃NH₃（MA）,HC（NH₂）₂（FA）,Cs;B=Pb,Sn;X=Cl,Br,I）具有高摩尔消光系数、可调的带隙、较低的激子束缚能和载流子双极性传输等特性,在电学、光学等领域的应用前景十分广阔。基于卤化物钙钛矿材料的太阳能电池具有效率高、成本低、可低温溶液制备、透明多彩等特点和优势,从而受到了学术界和产业界的广泛关注。尽管实验室认证效率已达到22.1%,但如何在实现高效率的同时保持稳定性是其产业化应用的关键。本论文从液态钙钛矿敏化太阳能电池出发,过渡到多种结构的全固态钙钛矿太阳能电池,围绕着提升器件效率和稳定性,开展了以下几个方面的研究工作:（1）本论文从基于液态电解质的p型敏化太阳能电池入手,对比研究了钙钛矿敏化和有机染料敏化太阳能电池的工作机理和性能差异。相较于传统p型染料敏化电池,钙钛矿敏化电池具有更高的器件效率（0.71%>0.15%）,表现在显著提高的的开路电压（205 mV）和短路电流密度（9.47 mA cm-2）。机理研究表明:在p型钙钛矿敏化太阳能电池中,喷雾热解形成的NiO致密层决定了电荷的流向。介孔NiO薄膜的存在,可以有效地抽取钙钛矿产生的光生电荷。但其自身的光吸收对电池的光捕获效率造成不利竞争,介孔孔洞对液态电解质的扩散传输也存在一定的限制作用。基于高效的p型钙钛矿敏化半电池,本论文进一步将其与n型染料敏化半电池构建成pn叠层电池,实现了消光范围的拓宽和开路电压的叠加,开路电压达到1050mV,同时电池光电转换效率达4.31%,显著超过同期国际pn叠层染料敏化太阳能电池1.91%的效率记录。（2）鉴于液态钙钛矿太阳能电池的不稳定性和介孔NiO自身颜色造成的光学损失,进一步开展固态反式平面型钙钛矿太阳能电池（结构为FTO玻璃/致密NiO/钙钛矿/PCBM/Bis-C60/Ag）的研究。通过两步连续法调控FAI_0.85MABr_0.15浓度从而制备高质量FA1-xMAxPb（I1-yBry）3混合钙钛矿薄膜。研究发现,当FAI_0.85MABr_0.15的浓度为40 mg mL-1,得到的钙钛矿薄膜的物相最纯、晶粒尺寸最大、荧光寿命最长。相应的最优化器件开路电压为1101 mV,短路电流密度为21.45 mA cm-2,填充因子为0.76,光电转换效率达到17.95%。而当FAI_0.85MABr_0.15浓度过低或过高时,钙钛矿薄膜中会残留一定量的PbI2或δ-FAPbI₃杂质相,这些杂质相对器件效率和稳定性有不同的影响。（3）针对有机空穴传输材料Spiro-MeOTAD导电性低、稳定性差、价格昂贵等缺点,采用无机铜铁矿结构的CuGaO₂纳米片取代Spiro-MeOTAD,构建“FTO玻璃/c-TiO₂/钙钛矿/CuGaO₂/Au”顺式结构太阳能电池。CuGaO₂纳米片作为空穴传输材料具有可低温涂布、空穴迁移率高(10-2¹01 cm² V^-1 s^-1)、化学稳定性高等优点,基于该材料,在获得更高的效率的同时,大幅提高了器件的稳定性。相比Spiro-MeOTAD的17.14%的效率,CuGaO₂器件的效率达到18.51%。由于CuGaO₂自身良好的化学稳定性和屏蔽作用,将CuGaO₂器件在室内空气中放置30天进行老化,器件的效率仍能保持初始值的80%。（4）基于印刷介孔电池结构“FTO玻璃/c-TiO₂/m-TiO₂/m-Al₂O₃/m-Carbon”,发展了一种MAPb I₃（SrCl2）x混合钙钛矿材料体系。与MAPbI₃相比,混合钙钛矿材料不仅减少有毒Pb的用量,而且可以改善混合钙钛矿在介孔电极中的填充状态,且形成一种特殊的结晶形态,能够有效钝化钙钛矿缺陷态,使得钙钛矿中载流子复合寿命显著延长（180 ns>67 ns）。器件的光电转换效率由MAPbI₃的12.63%提高至MAPb I₃（SrCl₂）_0.1混合钙钛矿的15.90%。同时,混合钙钛矿器件的稳定性也得到进一步的改善,该器件在不封装情况下在白光LED照射1000 h后,效率仍保留了初始值的90%。更多还原

【Abstract】 Organic-inorganic halide perovskites,denoted as ABX₃ [A = Cs+,CH₃NH₃⁺（MA⁺）,or NH=CHNH₃⁺（FA+）;B = Pb or Sn;X = Br,I or Cl],have recently attracted researchers’ great interest owning to their outstanding advantages as light absorbers for photovoltaic applications,such as direct and appropriate band gap,large absorption coefficient,high carrier mobility as well as ambipolar charge transport.Organic-inorganic halide perovskite solar cell（PSC）encourages even more efforts of the research community from both academia and industry to expedite the commercialization process because of its high efficiency,low-cost,low temperature process,transparency and mutiple color.Although the certified power conversion efficiency（PCE）for PSC have yeiled to 22.1%,the major challenge for bringing this technology for commercialization lies in its long-term environmental stability.In this thesis,we firstly explored p type perovskite sensitized solar cell.To improve efficiency and stability of PSC,four main approaches has been used:（1）In this work,we demonstrated effective photocathodes based on novel organometal halide perovskites sensitized mesoporous NiO in liquid electrolyte based p-type solar cells.A decent Voc and Jsc up to 205 mV and 9.47 mA cm^-2 have been achieved based on the MAPb I₃/NiO solar cell at 100 mW cm^-2 light intensity,which is significantly higher than any of previously reported liquid electrolyte based p-type solar cells based on sensitizers of organic dyes or inorganic quantum dots.The dense blocking layer made by spray pyrolysis of nickel acetylacetonate holds the key on determining the current flow direction of the solar cells.The good research basis allows us to firstly design a novel pn tandem solar cell by combination of organic dye（N719）sensitized n-type TiO₂ photoanode and organometal halide（MAPb I₃-xClx）sensitized p-type NiO photocathode,by sharing the same iodine liquid electrolyte.The Voc of our tandem cell reached 1050 mV with efficiency up to 4.31% which is also superior to most of previously reported pn dye sensitized tandem solar cells with efficiency of 1.91%.（2）However a rapid degradation of performance was witnessed due to dissolution of the perovskite in the I₃-/I-electrolyte.Considering the structure of solid-state dye sensitized and organic solar cells,many researchers developed a new solid-state solar cells（FTO glass/c-NiO/perovskite/PCBM/Bis-C60/Ag）employing FA1-xMAxPb（I1-yBry）3 perovskite as a light absorber.FA1-xMAxPb（I1-yBry）3 compositional perovskite recently was frequently reported in high efficiency PSCs,benefiting from their high quality crystal,tunable bandgaps,wide absorption spectrum and stability.In this work,a two-step method by inter-diffusion of spin-coated stacking layers of PbI2 and FAI_0.85MABr_0.15 has been implemented to fabricate high quality FA0.85MA0.15Pb（I0.85Br0.15）3 films.By optimizing the concentrations of FAI_0.85MABr_0.15 to 40 mg mL-1,high quality FA0.85MA0.15Pb（I0.85Br0.15）3 films are formed with pure perovskite phase,larege scale crystal and long lifetime.Applied this compositional perovskite into inverted FTO glass/c-NiO/ PCBM/perovskite/Bis-C60/Ag,Voc,Jsc and FF have reached 1101 mV,21.45 mA cm-2 and 0.76 with high efficiency with 17.95%.We also found unreacted Pb I2 and δ-FAPb I₃ had effect on the stability of PSC.（3）For the regular n-i-p configuration PSC,the hole-transporting layer（HTL）used so far is mainly based on p-type organic semiconductors such as Spiro-OMeTAD,which is relative high cost,low conductivity and tend to interact with water.CuGaO₂ shows low-temperature solution process,higher mobility and stability,which is very promising hole transport layer candidate for improving photovoltaic performance,device stability,and fabrication cost of PSC.By applying CuGaO₂ into FTO glass/c-TiO₂/perovskite/CuGaO₂/Au structure,high efficiency with 18.51% has reached.Moreover,the CuGaO₂ layer with high hole mobility and environmental stability helps isolate the perovskite and Au layers to significantly enhance device’s photovoltaic performance and long-term stability（with > 80% of its initial PCE remained after 30-days storage in air at room temperature）.（4）Full printable processed mesoscopic perovskite solar cell with carbon as cathode has draw wide concern for its’ long-term stability.In this work,a new compositional perovskite MAPbI₃（SrCl₂）_x thereafter has been introduced into this architecture.We chemically modify the MAPbI₃ perovskite by substituting PbI₂ with SrCl₂ in the precursor solution.Structural,elemental,and morphological analyses show that the incorporation of SrCl₂ affords the formation of MAPbI₃（SrCl₂）_x perovskites endowed with lower defect concentration and better pore filling in the derived mesoscopic PSCs.By employing MAPb I₃（SrCl₂）_0.1 into FTO glass/c-TiO₂/m-TiO₂/m-Al₂O₃/m-Carbon structure showed PCE of 15.90%.Besides enhanced PCE,the MAPbI₃（SrCl₂）_0.1 based PSC also affords an improved stability.Exposing unencapsulated MAPb I₃（SrCl₂）_0.1 based PSC to 10 mW cm^-2 light intensity using white LED for 1000 h,the PCE remained 90% of the initial value.更多还原