Specific point was achieved for flexible MAPbI3 solar cells with CPTA modified SnO2 ETL.

For solar cell applications, Sn-based hybrid perovskites have drawn particular interest due to their environmental friendliness. Here, a thin layer of C 60 pyrrolidine tris-acid (CPTA) is found essential for achieving high efficiency with planar solar cells of Sn-based perovskites. As a result, a power conversion efficiency of 7.40% is achieved for {en}FASnI 3 solar cells with a planar n-i-p architecture, and the device exhibits excellent stability in air. For the first time, highly efficient Sn-based hybrid perovskite solar cells on n-i-p architecture are achieved. A V oc of 0.72 V is highlighted as the highest V oc ever reported for FASnI 3 solar cells.The ORCID identification number(s) for the author(s) of this article can be found under https://doi.org/10.1002/adfm.201903621. and sometimes even short-circuit the devices. Several strategies have been developed to protect the Sn-based perovskite, such as the adding of SnF 2 , [10] controlling the reducing atmosphere, [11] the forming of 2D/3D composite [12,13] or 3D hollow structures. [14][15][16][17] In order to achieve higher efficiency and stability, Sn-based perovskite have relied on mesoporous TiO 2 as the electron-selective layer. [18,19] The introduction of mesoporous TiO 2 makes manufacture process more complex, and the high-temperature needed for processing hampers the development of perovskitebased monolithic tandem devices and flexible wearable solar cells. [20,21] In contrast, the simplicity of the planar heterojunction indicates that a planar architecture is more technically feasible. [22] Besides, planar PSCs can be fabricated via solution processing at low temperatures (<150 °C), thus greatly reducing manufacturing costs. However, compared to the mesoporoustype PSC, its planar-type counterpart suffers from very low PCE, [23,24] probably due to the poor contact of the interfaces [25] and unsuitable charge transporting layer. [23] Here, we tried SnO 2 as the electron transport layer to fabricate a n-i-p planar-architecture, but was not successful. Then we introduced a hydrophilic derivative of fullerene, namely, the C 60 pyrrolidine tris-acid (CPTA) between SnO 2 and the perovskite. As a result, we achieved a power conversion efficiency above 7.40% for Sn-based perovskite devices with the planar architecture. This shows that not only mesoporous-architecture devices, but also n-i-p planar-architecture devices can be highly efficient in the Sn-based PSCs. Thanks to the CPTA layer in our planar Sn-based PSCs, we attained a V oc of 0.72 V, which represents the highest value ever reported for FASnI 3 solar cells. Results and DiscussionWe fabricated Sn-based PSCs with the planar n-i-p architecture (Figure 1a). A SnO 2 compact layer deposited on the fluorine-doped tin oxide (FTO) substrate was employed as an electron transport layer. C 60 pyrrolidine tris-acid (CPTA) was then deposited onto the SnO 2 -covered FTO substrate. Figure 1b shows the X-ray diffraction (XRD) pattern of the {en}FASnI 3 films. The peaks of FTO substrate are marked with black dots. ...

Porous carbons such as CMK-3 are commonly used as matrices to accommodate metal oxides for the improvement of their electrochemical performance. However, the mesostructure of CMK-3 may be destroyed gradually with the increase of metal oxide content and some particles are inevitably formed outside the pores of CMK-3, leading to a gradual decrease in capacity and poor cycling performance. Herein, graphene-encapsulated CMK-3-metal oxides (Fe3O4 and NiO) are synthesized through a stepwise heterocoagulation method and exhibit improved electrochemical performances compared to uncoated CMK-3-metal oxides. The core-shell structure of these novel composites can protect the metal oxide particles on the surface of CMK-3 and avoid the aggregation of porous carbon-metal oxides. Moreover, the introduction of graphene may stabilize the mesostructure of CMK-3 during lithiation and delithiation processes and improve the electronic conductivity of the composite, which are conducive to enhancing electrochemical performances of porous carbon-supported metal oxides.

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As a widely used substrate for flexible electronics, indium‐tin oxide‐based polymer electrodes (polymer‐ITO electrodes) exhibit poorly visible light transmittance of less than 80%. The inferior transmittance for polymer‐ITO electrodes severely limits the performance improvement of polymer‐ITO based electronics. Here, a conceptually different approach of the double‐sided antireflection coatings (DARCs) strategy is proposed to modulate both the air–polymer substrate interface and ITO–air interface refractive index gradient, to synergistically improve the transmittance of polymer‐ITO electrodes. On the basis of SiO2 nanoparticles antireflection layer on polymer substrate, a polymer–metal oxide composite antireflection film is fabricated on the ITO side. Resultantly, the transmittance of ITO‐based flexible electrodes is successfully improved from 76.8% to 89.8%, which is the highest transmittance among the reported ITO‐based flexible electrodes. Furthermore, the photoluminescence emission intensity of luminescent materials enveloped with the DARCs electrodes increases by 74% over that with reference electrodes, demonstrating the DARCs antireflection strategy can efficiently improve the performance of flexible optoelectronic devices. With DARCs electrode, the flexible perovskite solar cells exhibit an enhanced efficiency from 18.80% to 20.85%.