ALD-Al_(2)O_(3)涂层保护的高抗湿5-氨基戊酸铰链甲胺铅溴钙钛矿薄膜

近年来,混合铅卤钙钛矿材料在光电领域引发的研究热潮引人注目。然而,钙钛矿材料对水和氧气的敏感性严重的阻碍了其实用化进程。在众多的稳定钙钛矿的方法中,利用简单的原子层沉积方法(Atomic layer deposition,ALD)在钙钛矿表面沉积一层保护层的技术具有极大的潜力。而ALD应用的困难在于,在常规的ALD过程中,做为氧源的H2O和O3对铅卤钙钛矿有着腐蚀作用。在本文,我们提出将双官能团的5-氨基戊酸(5-Aminovaleric acid,AVA)引入到CH_(3)NH_(3)PbBr_(3)(MAPbBr_(3))钙钛矿晶格层中,形成稳定的铰链结构的2D/3D钙钛矿AVA(MAPbBr_(3))2。AVA的引入可以钝化并防止ALD过程中水对钙钛矿的侵蚀,从而成功地直接在钙钛矿表面沉积了Al_(2)O_(3)保护层。覆盖了保护层的AVA(MAPbBr_(3))2钙钛矿薄膜获得了优异的热稳定性和抗水性。

Synergistic stabilization of CsPbI_(3) inorganic perovskite via 1D capping and secondary growth

Cesium lead iodide(CsPbI_(3)) perovskite has gained great attention in the photovoltaic(PV) community because of its unique optoelectronic properties, good chemical stability and appropriate bandgap for sunlight harvesting applications. However, compared to solar cells fabricated from organic-inorganic hybrid perovskites, the commercialization of devices based on all-inorganic CsPbI_(3) perovskites still faces many challenges regarding PV performance and long-term stability. In this work, we discovered that tetrabutylammonium bromide(TBABr) post-treatment to CsPbI_(3) perovskite films could achieve synergistic stabilization with both TBA+cation intercalation and Br-doping. Such TBA^(+) cation intercalation leads to onedimensional capping with TBAPb I3 perovskite formed in situ, while the Br-induced crystal secondary growth helps effectively passivate the defects of CsPbI_(3) perovskite, thus enhancing the stability. In addition, the incorporation of TBABr can improve energy-level alignment and reduce interfacial charge recombination loss for better device performance. Finally, the highly stable TBABr-treated CsPbI_(3)-based perovskite solar cells show reproducible photovoltaic performance with a champion efficiency up to 19.04%, while retaining 90% of the initial efficiency after 500 h storage without encapsulation.

Cs-content-dependent organic cation exchange in FA1-xCsxPbI3 perovskite

FA-Cs mixed-cation perovskite has been reported as a promising candidate for obtaining highly efficient and stable photovoltaic devices.Phenylethylamine iodide(PEAI)post-treatment is a widely used and effective method for surface passivation of FA-Cs perovskite layer in devices.However,it is still controversial whether the PEAI post-treatment would form two-dimensional(2D)perovskite PEA_(2)PbI_(4) capping layer or just result in PEA+terminated surface.Here in this work,the function of PEAI post-treatment on FA-Cs mixed-cation perovskite FA_(1-x)Cs_(x)PbI_(3)(x=0.1–0.9)with varied Cs contents is elucidated.With increased Cs content,the FA-Cs perovskite shows higher resistance to the cation exchange between FA+and PEA+.This Cs-content-dependent cation exchange results in the different PEAI reaction preferences with FA-Cs mixed-cation perovskites.Furthermore,higher Cs content with stronger resistance to cation exchange reaction leads to a wider processing window for post-treatment and defect passivation,which is beneficial for the fabrication of large-scale photovoltaic devices.

功能型有机阳离子诱导实现CsPbI_(3)全无机钙钛矿三维至零维晶相转化与表面重构

铅卤钙钛矿太阳能电池兼具高效率和低成本的突出优势,近年来研究进展迅速、应用前景广阔,对于进一步推进光伏产业发展、实现碳中和目标具有重要意义.相比于有机无机杂化钙钛矿,CsPbI_(3)全无机钙钛矿具有更高的化学稳定性,但同时也面临着缺陷密度较高的挑战,制约了该组分电池器件效率的进一步提升.钙钛矿表面重构是一种降低缺陷密度的有效方法,但受限于全无机结构中铅碘八面体与铯离子之间较强的离子键作用,诱发无机钙钛矿表面二次生长的困难远高于杂化钙钛矿体系.本文通过选取辛基十二烷基二甲基铵这一特殊的季铵阳离子,成功实现了CsPbI_(3)钙钛矿薄膜的表面重构与三维至零维的原位晶相转化.在这种功能型季铵溴盐的诱导作用下,零维Cs_(4)bI_(6)在CsPbI_(3)薄膜的表面晶界处原位生成,有效钝化了缺陷,提高了结构稳定性.基于表面重构与缺陷钝化的无机钙钛矿太阳能电池获得了20.63%的高光电转换效率,实现了长期的高效稳定运行.

Solution chemistry quasi-epitaxial growth of atomic CaTiO_(3)perovskite layers to stabilize and passivate TiO_(2)photoelectrodes for efficient water splitting

Perovskite oxides with unique crystal structures and high defect tolerance are promising as atomic surface passivation layers for photoelectrodes for efficient and stable water splitting.However,controllably depositing and crystalizing perovskite-type metal oxides at the atomic level remains challenging,as they usually crystalize at higher temperatures than regular metal oxides.Here,we report a mild solution chemistry approach for the quasi-epitaxial growth of an atomic CaTiO_(3)perovskite layer on rutile TiO_(2)nanorod arrays.The high-temperature crystallization of CaTiO_(3)perovskite is overcome by a sequential hydrothermal conversion of the atomic amorphous TiOx layer to CaTiO_(3)perovskite.The atomic quasi-epitaxial CaTiO_(3)layer passivated TiO_(2)nanorod arrays exhibit more efficient interface charge transfer and high photoelectrochemical performance for water splitting.Such a mild solution-based approach for the quasi-epitaxial growth of atomic metal oxide perovskite layers could be a promising strategy for both fabricating atomic perovskite layers and improving their photoelectrochemical properties.

MA Cation-Induced Diffusional Growth of Low-Bandgap FA-Cs Perovskites Driven by Natural Gradient Annealing

Low-bandgap formamidinium-cesium(FA-Cs)perovskites of FA_(1-x)CsxPbI_(3)(x<0:1)are promising candidates for efficient and robust perovskite solar cells,but their black-phase crystallization is very sensitive to annealing temperature.Unfortunately,the low heat conductivity of the glass substrate builds up a temperature gradient within from bottom to top and makes the initial annealing temperature of the perovskite film lower than the black-phase crystallization point(~150℃).Herein,we take advantage of such temperature gradient for the diffusional growth of high-quality FA-Cs perovskites by introducing a thermally unstable MA^(+)cation,which would firstly formα-phase FA-MA-Cs mixed perovskites with low formation energy at the hot bottom of the perovskite films in the early annealing stage.The natural gradient annealing temperature and the thermally unstable MA^(+)cation then lead to the bottom-to-top diffusional growth of highly orientatedα-phase FA-Cs perovskite,which exhibits 10-fold of enhanced crystallinity and reduced trap density(~3:85×10^(15) cm^(−3)).Eventually,such FA-Cs perovskite films were fabricated into stable solar cell devices with champion efficiency up to 23.11%,among the highest efficiency of MA-free perovskite solar cells.

In situ growth of ultra-thin perovskitoid layer to stabilize and passivate MAPbI_(3)for efficient and stable photovoltaics

The efficiency and stability of typical three-dimensional(3D)MAPbI_(3)perovskite-based solar cells are highly restricted,due to the weak interaction between methylammonium(MA^(+))and[PbI 6]4-octahedra in the 3D structure,which can cause the ion migration and the related defects.Here,we found that the in situ-grown perovskitoid TEAPbI_(3)layer on 3D MAPbI_(3)can inhibit the MA^(+)migration in a polar solvent,thus enhancing the thermal and moisture stability of perovskite films.The crystal structure and orientation of TEAPbI_(3)are reported for the first time by single crystal and synchrotron radiation analysis.The ultra-thin perovskitoid layer can reduce the trap states and accelerate photo-carrier diffusion in perovskite solar cells,as confirmed by ultra-fast spectroscopy.The power conversion efficiency of TEAPbI_(3)-MAPbI_(3)based solar cells increases from 18.87%to 21.79%with enhanced stability.This work suggests that passivation and stabilization by in situ-grown perovskitoid can be a promising strategy for efficient and stable perovskite solar cells.