【作者】 李骏；

【导师】 陈红征；

【作者基本信息】 浙江大学 ， 高分子材料， 2021， 博士

【摘要】 有机-无机杂化钙钛矿具有吸收可调、激子扩散距离长、缺陷态密度低等特性,是目前光电领域的研究热点。该类材料可以溶液法加工,制备成质量轻的柔性器件,在光电领域具有明显的优势。经过十多年的研究发展,三维有机-无机杂化钙钛矿太阳电池器件在效率上实现了从3.8%到25.5%的飞跃,能够与商业化应用的硅太阳电池器件相媲美。然而,三维有机-无机杂化钙钛矿太阳电池器件在稳定性上仍存在缺陷,对光、热、水、氧等敏感,这也制约了钙钛矿太阳电池的商业化应用。为了解决这一问题,研究者通过在三维钙钛矿中引入间隔阳离子胺盐,形成层状钙钛矿结构,即准二维钙钛矿。利用二维钙钛矿较高的形成能和疏水特性,可以制备得到稳定的钙钛矿光伏器件。然而,由于间隔阳离子胺盐上有机长链的绝缘性和空间位阻效应,其形成的有机层成为钙钛矿无机层之间电荷传输的阻隔。因此,本论文拟通过合成具有分子间氢键作用的新型间隔阳离子胺盐,利用氢键作用缩短钙钛矿无机层间距,改善无机层之间的电荷传输性能。然后,我们将这种新型间隔阳离子胺盐引入三维钙钛矿体系构建二维/三维钙钛矿体系,研究并分析新型间隔阳离子胺盐在三维钙钛矿体系中的作用及机理。最后,我们在反型三维钙钛矿器件中系统研究了间隔阳离子胺盐界面修饰的作用及其机理。在论文的第二章中,我们设计并合成了具有分子间氢键作用的新型间隔阳离子胺盐4-氨基乙基吡啶氢碘酸盐（4-AEPI）,并基于4-AEPI构建了新型二维钙钛矿体系,（4-AEP）₂MA_n-1Pb_nI_3n+1,并以n=9的体系制备了二维钙钛矿太阳电池器件。我们通过对（4-AEP）₂Pb I₄和PEA₂Pb I₄钙钛矿薄膜进行X射线衍射（XRD）表征以及对（4-AEP）₂MA₈Pb₉I₂₈和（PEA）₂MA₈Pb₉I₂₈钙钛矿器件性能和钙钛矿薄膜载流子迁移率的表征和对比证明4-AEPI的分子间氢键作用缩短了二维钙钛矿薄膜中钙钛矿无机层间距,改善了无机层之间的电荷传输性能,可以获得1.94%的效率。我们通过硫氰酸甲铵（MASCN）添加剂进一步优化二维钙钛矿电池器件性能,并通过扫描电子显微镜（SEM）表征发现添加剂可以使晶粒增大,改善了钙钛矿薄膜形貌,并成功将器件效率从1.94%进一步提高至9.07%,并具有很好的水氧稳定性。在论文的第三章中,我们尝试将新型间隔阳离子胺盐4-AEPI以添加剂的形式掺入到三维钙钛矿太阳电池器件中以钝化钙钛矿薄膜中的缺陷。我们系统的研究了4-AEPI掺入摩尔比对器件性能的影响,在掺入摩尔比为0.3%时成功将器件效率从17.37%提高至18.27%,并且水氧稳定性也得到了改善。我们通过空间电荷限制电流（SCLC）的方法证明器件性能改善的主要原因是4-AEPI钝化了钙钛矿薄膜中的缺陷,降低了缺陷密度。在论文的第四章中,我们采用了间隔阳离子胺盐底表面修饰的方法改善反型三维钙钛矿器件的性能,并发现在采用不同类型的间隔阳离子胺盐（包括R-P类型苯乙胺氢碘酸盐（PEAI）、D-J类型对苯二甲胺二碘盐（PDMAI₂）和具有强配位作用的4-AEPI）时,器件效率均可以从20.65%提高至21.6%以上,器件的水氧稳定性和热稳定性也得到了改善。在研究过程中,我们创新性的采用了lift-off方法将钙钛矿薄膜剥离下来,可以对钙钛矿薄膜底表面直接进行表征,这对钙钛矿器件界面研究具有重要意义。通过表征和分析,我们认为器件性能改善的主要原因是界面形成的二维/三维异质结结构有效钝化了界面缺陷、改善了空穴提取和抑制了载流子复合,从而降低了开路电压损失,并提高了填充因子。更多还原

【Abstract】 Organic-inorganic hybrid perovskite solar cells(PVSCs)have drawn tremendous attention due to their merits such as tunable absorption profile,long exciton diffusion length,low defect density and so on.It can also be easily prepared by solution method to fabricate light-weight flexible devices at low cost.After more than ten years of research and development,the efficiency of 3D organic-inorganic hybrid perovskite has surged from 3.8% to 25.5%,which is comparable to that of commercial siliconbased solar cells.However,the stability of 3D organic-inorganic hybrid perovskite solar cells is still inferior,and the PVSCs has been demonstrated sensitive to light,heat,water and oxygen.This constitutes the major limitation for commercialization of PVSCs.To address this issue,researchers intend to incorporate spacer ammonium salts into 3D perovskite systems to form the layered perovskite systems,namely quasi-2D perovskite.However,due to the wide band gap and steric hindrance effect of the organic long chain of the spacer ammonium salts,charge transport between inorganic perovskite slabs is hindered.To address this issue,we synthesized novel spacer ammonium salts featuring strong intermolecular hydrogen bonding,in order to shorten the interlayer distance of the inorganic perovskite slabs and improve the charge transport property between inorganic slabs.Besides,this novel spacer ammonium salt was introduced into 3D perovskite devices,and the effect and mechanism of the spacer ammonium salt in 3D perovskite system were studied.Further,we incorporate spacer ammonium salts on top/bottom of the 3D layer to form the 2D/3D heterojunction.The effects and underlying mechanism of 2D/3D interface modification sites and types of spacer ammonium salts on the performance of the inverted 3D perovskite devices were comprehensively studied.In the second chapter,we synthesized a novel spacer ammonium iodide salt,i.e.,4-amino ethyl pyridine iodide(4-AEPI),with intermolecular hydrogen bonding,and constructed the quasi-2D perovskite system,(4-AEP)2MAn-1Pbn I3n+1,and fabricated quasi-2D PVSCs based on n=9 2D system.The results of X-ray diffraction(XRD)of(4-AEP)2Pb I4 and(PEA)2Pb I4 films and the device performance and carrier mobilities based on(4-AEP)2MA8Pb9I28 and(PEA)2MA8Pb9I28 films show that the intermolecular hydrogen bonding of 4-AEPI shortens the distance between inorganic slabs in the 2D perovskite films,which improves the charge transport between inorganic slabs and enables an efficiency of 1.94%.The device performance of 2D PVSCs was further optimized by using ammonium thiocyanate(MASCN)additive,and the scanning electron microscope(SEM)characterization shows that the additive could effectively increase the grain size and improve the morphology of perovskite films,leading to improved efficiency from 1.94% to 9.07%.In the third chapter,we tried to incorporate the novel spacer ammonium salts 4-AEPI into the 3D perovskite system as an additive to passivate the defects in bulk perovskite films.We systematically studied the effect of 4-AEPI content on the performance of the device.With 0.3% molar ratio of 4-AEPI,the efficiency of the devices was improved from 17.37% to 18.27%.Space charge limited current(SCLC)method proves that 4-AEPI passivates the defects in perovskite films and decreases the defect density,and this contributes to the enhancement of device performance.In the fourth chapter of this paper,we used different spacer ammonium salts,including R-P type phenyl ethyl ammonium iodide(PEAI),D-J type 1,4-phenyl dimethyl ammonium iodide(PDMAI2)and strong-complexation type 4-AEPI,to modify the bottom interface of 3D perovskite films.With the different types of spacer ammonium salts,the device efficiency can be universally improved from 20.65% to over 21.6%.Further,we used the lift-off method to peel off the perovskite films,and for the first time,the mechanism of bottom interface modification with spacer ammonium salts is directly studied and identified.Through the direct characterization and analysis,we demonstrate that the improvement of device performance with different types of spacer ammonium salts is universally attributed to 2D/3D heterojunction formed at the interface,which passivates the defects at the interface,improves the hole collection and suppresses the charge recombination,which reduces the open circuit voltage loss and improves the fill factor.更多还原