The defect control of polycrystalline perovskite films is essential for achieving an efficient and stable perovskite solar cell (PSC). However, existing methods of reducing defects suffer from their complex processes, low durability, and limited effects by using molecular materials in terms of passivation mechanisms. Herein, a hybrid film composed of SnO 2 nanoparticles/Ti 3 C 2 T x MXene nanoflakes is used as the electron transport layer (ETL) in a planar regular-structure PSC. The results indicate that by changing the Ti 3 C 2 T x /SnO 2 ratios (0−2.2 wt %) in ETLs, the film qualities of top perovskite layers are controllable, including the compactness, crystal size, surface roughness, crystallinity, optical absorption, defect density, and so forth. The defect density in perovskite films is substantially reduced from 5.65 × 10 15 to 2.25 × 10 15 cm −3 using an optimized hybrid ETL (1.4 wt %) compared with the pristine SnO 2 , while the electrical conductivity of the hybrid ETL is decreased probably due to the geometric factor of the incorporated MXene. As a result, the power conversion efficiency of PSCs is significantly increased from 16.28 to 20.35%, and the environmental stability of the unencapsulated devices is greatly improved. This work provides a facile, robust, and effective way to reduce defects in perovskite films by using emerging MXene nanomaterials and might also be useful to other perovskite-based (opto)electronic devices such as light-emitting diodes and photodetectors.

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Since its discovery in 2011, the Ti3C2Tx MXene has attracted more and more attentions in diverse fields such as photocatalysis, energy storage, and electromagnetic shielding interference etc., due to its unique layered structure, high specific surface area, high conductivity, catalytic activity and easy functionalization. In recent years, attributed to its excellent light-to-heat conversion property, good selective adsorption and effective reduction feature for heavy metal ions, the Ti3C2Tx MXene has appealed new attentions in water treatment. This review mainly summarizes the latest research progresses on Ti3C2Tx MXene in water treatment. Firstly, the synthesis methods in recent years, characterizations and surface modifications of Ti3C2Tx MXene are briefly summarized. Then the application progresses and mechanisms of Ti3C2Tx MXene in solar desalination, removal of heavy metal ions, organic dyes, radionuclides and bacteria are introduced. Finally, the main challenges and prospects of Ti3C2Tx MXene based nanomaterials are proposed. This review provides a reference for further research on water treatment, and might promote the practical application of nanomaterials in water treatment from the laboratory research.

The composition and crystallization process are essential for high-quality perovskite films. Cesium (Cs) and methylammonium chlorine (MACl) were found to affect the crystallization kinetics of perovskite, and the performance and stability of corresponding devices were greatly improved. We adopted an ion exchange method to remove MACl vapor and add Cs to form a multiple-cation-based perovskite film. With the increase of annealing time, Cl − from cesium chloride (CsCl) and MA from methylammonium bromide (MABr) formed gradually MACl vapor, and the porosity of surface morphology improved accordingly. The highly crystallized and compact Cs y MA x − y FA 1 − x PbI 3 − x Br x perovskite film with different compositions was eventually obtained. The effects of the amount of MABr on the property of perovskite films and on the performance of the corresponding perovskite solar cells (PerSCs) were systematically studied. The PerSCs derived from 12 mg of MABr exhibit the best photovoltaic performance with a power conversion efficiency of 21.57% under 1 sun illumination.

: In the past decade, organic-inorganic perovskite solar cells (PSCs) have received great attentions due to their high efficiencies and low costs. However, the commercialization of PSCs is stilled hindered by several issues such as device performance (especially for large-area cells) and stability. Recently, two-dimensional (2D) transition metal disulfides (TMDs) show great potentials in solving aforementioned problems due to their unique morphological structure and electrical properties. Herein, we summarize the advancements in the recent applications of various TMDs materials as charge transport layers in PSCs. Although some progresses have been made, there are considerable issues to be tackled in this field. The challenges and development directions of these 2D TMDs materials for PSCs are also clarified. Lastly, the most recent advancements about TMDs materials in some other electronic (or optoelectronic) fields are also summarized and discussed.