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.

Recent Progress in Large-Area Perovskite Photovoltaic Modules

Perovskite solar cells(PSCs)have undergone a dramatic increase in laboratory-scale effi ciency to more than 25%,which is comparable to Si-based single-junction solar cell effi ciency.However,the effi ciency of PSCs drops from laboratory-scale to large-scale perovskite solar modules(PSMs)because of the poor quality of perovskite fi lms,and the increased resistance of large-area PSMs obstructs practical PSC applications.An in-depth understanding of the fabricating processes is vital for precisely controlling the quality of large-area perovskite fi lms,and a suitable structural design for PSMs plays an impor-tant role in minimizing energy loss.In this review,we discuss several solution-based deposition techniques for large-area perovskite fi lms and the eff ects of operating conditions on the fi lms.Furthermore,diff erent structural designs for PSMs are presented,including the processing technologies and device architectures.

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.

Microcavity top-emission perovskite light-emitting diodes

Light-emitting diodes(LEDs)based on perovskites show great potential in lighting and display applications.However,although perovskite films with high photoluminescence quantum efficiencies are commonly achieved,the efficiencies of perovskite LEDs are largely limited by the low light out-coupling efficiency.Here,we show that high-efficiency perovskite LEDs with a high external quantum efficiency of 20.2% and an ultrahigh radiant exitance up to 114.9mWcm^(−2) can be achieved by employing the microcavity effect to enhance light extraction.The enhanced microcavity effect and light outcoupling efficiency are confirmed by the study of angle-dependent emission profiles.Our results show that both the optical and electrical properties of the device need to be optimized to achieve high-performance perovskite LEDs.

The formation of perovskite multiple quantum well structures for high performance light-emitting diodes

Recent works showed that high efficient perovskite light-emitting diodes can be achieved from solution-processed,self-organized multiple quantum wells(MQWs)with an energy cascade.We investigate how the mixing of QWs with different band gaps can affect the perovskite LED device performance.We find that the annealing process can significantly affect the constitution of the MQWs films,where the dominant phase can evolve from large band gap QWs to small band gap QWs.The optimal constitution for LED application lies in a transition point of small-n QWs dominant phase to large-n QWs dominant phase,when the MQW film presents highest photoluminescence while still remains uniform film morphology.

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.