As the most promising lead‐free one, tin‐halides based perovskite solar cells still suffer from the severe bulk‐defect due to the easy oxidation of tin from divalent to tetravalent. Here, a general and effective strategy is delivered to modulate the microstructure of 2D/3D heterogeneous tin‐perovskite absorber films by substituting FAI with FPEABr in FASnI3. The introduction of 2D phase can induce highly oriented growth of 3D FASnI3 and it is revealed in the optimal 2D/3D film that 2D phase embraces 3D grains and locates at the surfaces and grain boundaries. The FPEA+ based 2D tin‐perovskite capping layer can offer a reducing atmosphere for vulnerable 3D FASnI3 grains. The unique microstructure effectively suppresses the well‐known oxidation from Sn2+ to Sn4+, as well as decreasing defect density, which leads to a remarkable enhanced device performance from 9.38% to 14.81% in conversion efficiency. The certified conversion efficiency of 14.03% announces a new record and moves a remarkable step from the last one (12.4%). Besides of this breakthrough, this work definitely paves a new way to fabricate high‐quality tin‐perovskite absorber film by constructing effective 2D/3D microstructures.

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Wearable and portable devices contribute to a rapidly growing emerging market for electronics and can find wide applications for wireless communications, multifunctional entertainments, personal healthcare monitoring, etc. [1][2][3][4][5] Typically, wearable devices with attractive attributes such as flexibility, long cruising time, and operation safety are highly desirable. [6][7][8][9][10][11] Recent advances in fields of power generation devices enable sustainable energy harvesting from the environment, such as solar energy, mechanical vibrations and frictions, biofluid and thermal energy from human body, and converted into electricity without external power sources, which introduces the concept of "self-powered" systems. [12][13][14][15][16][17] To realize continuous operation of the entire self-powered devices without interruption from surrounding conditions variation, such as insufficient solar illumination, fully integrated self-powered systems that consist of energy harvesting/conversion devices (e.g., solar cells, nanogenerators, biofuel cells), energy storage devices as intermediate energy storage units (e.g., rechargeable batteries, supercapacitors) and functional devices (e.g., sensors, transistors, biomedical implants) are highly desirable. [18] Planar supercapacitors with interdigitated electrodes constructed on single substrate emerged as one of the highly competitive energy storage devices to complement/replace batteries, offering merits of high power density, separator-free architectures for device miniaturization, and favorable operational safety without using flammable electrolytes. [19][20][21][22] Especially for integration with energy harvesting devices dealing with highly volatile energy input, particularly in wearable applications, supercapacitors possess an appealing capability to accommodate fast and high charging current fluctuation. [23][24][25][26] Although self-sufficient energy modules (e.g., photovoltaic-batteries, nanogenerator-supercapacitors) and selfpowered sensors (e.g., nanogenerator-sensors, battery-sensors) have been reported previously, [12,23,[26][27][28][29][30][31][32] to our best knowledge, demonstration of a fully integrated self-powered sensor system on flexible substrate implemented via additive printable strategy is rarely achieved, mainly due to the challenges on fabrication procedures compatibility and system integration of different device components.Wearable and portable devices with desirable flexibility, operational safety, and long cruising time, are in urgent demand for applications in wireless communications, multifunctional entertainments, personal healthcare monitoring, etc. Herein, a monolithically integrated self-powered smart sensor system with printed interconnects, printed gas sensor for ethanol and acetone detection, and printable supercapacitors and embedded solar cells as energy sources, is successfully demonstrated in a wearable wristband fashion by utilizing inkjet printing as a proof-of-concept. In such a "wearable wristband", the harvested so...

The promising tin perovskite solar cells (PSCs) suffer from the oxidation of Sn2+ to Sn4+, leading to a disappointing conversion efficiency along with poor stability. In this work, phenylethylammonium bromide (PEABr) was employed to form an ultrathin, low‐dimensional perovskite layer on the surface of the FASnI3 (FA=formamidinium) absorber film to improve the interface of perovskite/PCBM ([6,6]‐phenyl‐C61‐butyricacid methyl) in the inverted planar device structure of the ITO (indium‐doped tin oxide)/PEDOT:PSS [poly(3,4‐ethylenedioxythiophene)/polystyrene sulfonate]/perovskite/[6,6]‐phenyl‐C61‐butyricacid methyl (PCBM)/BCP (2,9‐dimethyl‐4,7‐diphenyl‐1,10‐phenanthroline) electrode. The device efficiency was enhanced from 4.77 to 7.86 % by this PEABr treatment. A series of characterizations proved that this modification could improve the crystallinity of the FASnI3 perovskite by incorporating Br and forming an ultrathin, low‐dimensional perovskite layer at the interface, which led to the effective suppression of Sn2+ oxidation, improved band level alignment, and decreased defect density. These effects contributed to the clear enhancement of conversion efficiency. Moreover, this treatment also led to remarkably enhanced device stability, with approximately 80 % of the initial efficiency retained after 350 h light soaking, whereas the control device failed within 140 h. This work deepens our understanding of the suppression effect of PEABr on the oxidation of Sn2+ and paves a new way to fabricate promising tin halide PSCs by facile interface engineering.

Phase transition driven bandgap aberration of Cs3Bi2I9−xBrx perovskites by varying x was discovered for the first time.

As the most promising lead‐free branch, tin halide perovskites suffer from the severe oxidation from Sn2+ to Sn4+, which results in the unsatisfactory conversion efficiency far from what they deserve. In this work, by facile incorporation of methylammonium bromide in composition engineering, formamidinium and methylammonium mixed cations tin halide perovskite films with ultrahighly oriented crystallization are synthesized with the preferential facet of (001), and that oxidation is suppressed with obviously declined trap density. MA+ ions are responsible for that impressive orientation while Br‐ ions account for their bandgap modulation. Depending on high quality of the optimal MA0.25FA0.75SnI2.75Br0.25 perovskite films, their device conversion efficiency surges to 9.31% in contrast to 5.02% of the control formamidinium tin triiodide perovskite (FASnI3) device, along with almost eliminated hysteresis. That also results in the outstanding device stability, maintaining above 80% of the initial efficiency after 300 h of light soaking while the control FASnI3 device fails within 120 h. This paper definitely paves a facile and effective way to develop high‐efficiency tin halide perovskites solar cells, optoelectronic devices, and beyond.

No abstract

Perovskite solar cells (PSCs) commonly exhibit significant performance degradation due to ion migration through the top charge transport layer and ultimately metal electrode corrosion. Here, we demonstrate an interfacial management strategy using a boron chloride subphthalocyanine (Cl6SubPc)/fullerene electron-transport layer, which not only passivates the interfacial defects in the perovskite, but also suppresses halide diffusion as evidenced by multiple techniques, including visual element mapping by electron energy loss spectroscopy. As a result, we obtain inverted PSCs with an efficiency of 22.0% (21.3% certified), shelf life of 7000 hours, T80 of 816 h under damp heat stress (compared to less than 20 h without Cl6SubPc), and initial performance retention of 98% after 2000 hours at 80 o C in inert environment, 90% after 2034 h of illumination and MPP tracking in ambient for encapsulated devices and 95% after 1272 h outdoor testing ISOS-O-1, which is among the top device performance for the inverted PSCs.