Chunxiang Dall’Agnese

Bio: Chunxiang Dall’Agnese is an academic researcher from Jilin University. The author has contributed to research in topics: Perovskite (structure) & MXenes. The author has an hindex of 13, co-authored 30 publications receiving 519 citations. Previous affiliations of Chunxiang Dall’Agnese include Shinshu University & Centre national de la recherche scientifique.

SnO2–Ti3C2 MXene electron transport layers for perovskite solar cells

Abstract: MXenes, a class of two-dimensional (2D) transition metal carbides and nitrides, have a wide range of potential applications due to their unique electronic, optical, plasmonic, and other properties. Herein, we explore the use of the Ti3C2 MXene in organic–inorganic lead halide perovskite solar cells (PSCs). SnO2–Ti3C2 MXene nanocomposites with different contents of Ti3C2 (0, 0.5, 1.0, 2.0, and 2.5 wt‰) were used as electron transport layers (ETLs) in low-temperature processed planar-structured PSCs. Mixing SnO2 with 1.0 wt‰ Ti3C2 effectively increases the power conversion efficiency (PCE) from 17.23% to 18.34%, whereas the device prepared with pristine Ti3C2 as the ETL achieves a PCE of 5.28%. Photoluminescence and electrochemical impedance spectroscopy results reveal that metallic Ti3C2 MXene nanosheets provide superior charge transfer paths, enhancing electron extraction, electron mobility, and decreasing the electron transfer resistance at the ETL/perovskite interface, and thus leading to higher photocurrents. This work proposes a new field of application for MXenes and a promising method to increase the efficiency of solar cells.

2D MXenes as Co-catalysts in Photocatalysis: Synthetic Methods

Abstract: Since their seminal discovery in 2011, two-dimensional (2D) transition metal carbides/nitrides known as MXenes, that constitute a large family of 2D materials, have been targeted toward various applications due to their outstanding electronic properties. MXenes functioning as co-catalyst in combination with certain photocatalysts have been applied in photocatalytic systems to enhance photogenerated charge separation, suppress rapid charge recombination, and convert solar energy into chemical energy or use it in the degradation of organic compounds. The photocatalytic performance greatly depends on the composition and morphology of the photocatalyst, which, in turn, are determined by the method of preparation used. Here, we review the four different synthesis methods (mechanical mixing, self-assembly, in situ decoration, and oxidation) reported for MXenes in view of their application as co-catalyst in photocatalysis. In addition, the working mechanism for MXenes application in photocatalysis is discussed and an outlook for future research is also provided.

Chlorophyll Derivative-Sensitized TiO2 Electron Transport Layer for Record Efficiency of Cs2AgBiBr6 Double Perovskite Solar Cells.

Abstract: The power conversion efficiency (PCE) of Cs2AgBiBr6-based perovskite solar cells (PSCs) is still low owing to the inherent defects of Cs2AgBiBr6 films. Herein, we demonstrate a carboxy-chlorophyll derivative (C-Chl)-sensitized mesoporous TiO2 (m-TiO2) film as an electron transport layer (ETL) to enhance and extend the absorption spectrum of Cs2AgBiBr6-based PSCs. The C-Chl-based device achieves a significantly improved PCE, exceeding 3% for the first time, with an increase of 27% in short-circuit current density. Optoelectronic investigations confirm that the introduction of C-Chl reduces the defects, accelerates the electron extraction, and suppresses charge recombination at the interface of ETL/perovskite. Moreover, the unencapsulated PSCs display restrained hysteresis and great stability under ambient conditions.

Surface-Modified Metallic Ti3C2Tx MXene as Electron Transport Layer for Planar Heterojunction Perovskite Solar Cells

Abstract: MXenes are a large and rapidly expanding family of 2D materials that, owing to their unique optoelectronic properties and tunable surface termination, find a wide range of applications including energy storage and energy conversion. In this work, Ti3C2Tx MXene nanosheets are applied as a novel type of electron transport layer (ETL) in low‐temperature processed planar‐structured perovskite solar cells (PSCs). Interestingly, simple UV‐ozone treatment of the metallic Ti3C2Tx that increases the surface TiO bonds without any change in its bulk properties such as high electron mobility improves its suitability as an ETL. Improved electron transfer and suppressed recombination at the ETL/perovskite interface results in augmentation of the power conversion efficiency (PCE) from 5.00% in the case of Ti3C2Tx without UV‐ozone treatment to the champion PCE of 17.17%, achieved using the Ti3C2Tx film after 30 min of UV‐ozone treatment. As the first report on the use of pure MXene layer as an ETL in PSCs, this work shows the great potential of MXenes to be used in PSCs and displays their promise for applications in photovoltaic technology in general.

Emerging 2D MXenes for supercapacitors: status, challenges and prospects.

Abstract: MXenes refer to a family of 2D transition metal carbides/nitrides that are rich in chemistry. The first member of the family, Ti3C2Tx, was reported in 2011. Since then MXenes have opened up an exciting new field in 2D inorganic functional materials by virtue of their intrinsic electronic conductivity, superior hydrophilicity, rich surface chemistry and layered structure, as evidenced by the fact that the number of papers on MXenes has increased exponentially. The unique properties and ease of processing have positioned them as promising materials for a variety of applications including energy storage, especially for supercapacitors. In this review, we aim to summarize the current advances in MXene research on supercapacitors. We begin by reviewing various fabrication routes and their influence on the structure and surface chemistry of MXenes. The structure, properties, stability, and species of layered MXenes are then introduced. The focus then turns to the capacitive energy-storage mechanisms and the factors determining the electrochemical behavior and performance in supercapacitors. Besides, various types of MXene-based supercapacitors are summarized to highlight the significance of MXenes in constructing energy storage devices. Finally, challenges and prospects in this booming field are proposed to promote further development of MXenes in supercapacitors.

Titanium-carbide MXenes for work function and interface engineering in perovskite solar cells.

Abstract: To improve the efficiency of perovskite solar cells, careful device design and tailored interface engineering are needed to enhance optoelectronic properties and the charge extraction process at the selective electrodes. Here, we use two-dimensional transition metal carbides (MXene Ti3C2Tx) with various termination groups (Tx) to tune the work function (WF) of the perovskite absorber and the TiO2 electron transport layer (ETL), and to engineer the perovskite/ETL interface. Ultraviolet photoemission spectroscopy measurements and density functional theory calculations show that the addition of Ti3C2Tx to halide perovskite and TiO2 layers permits the tuning of the materials’ WFs without affecting other electronic properties. Moreover, the dipole induced by the Ti3C2Tx at the perovskite/ETL interface can be used to change the band alignment between these layers. The combined action of WF tuning and interface engineering can lead to substantial performance improvements in MXene-modified perovskite solar cells, as shown by the 26% increase of power conversion efficiency and hysteresis reduction with respect to reference cells without MXene. Addition of MXenes in the halide perovskite film, in the electron transport layer and at the interface between these layers is shown to enhance the efficiency of and reduce hysteresis in perovskite solar cells.