Organic Dye/Cs2AgBiBr6 Double Perovskite Heterojunction Solar Cells.

The photovoltaic performance of Cs2AgBiBr6 perovskite is limited by its light-harvesting ability owing to its broad bandgap. Here, we introduced three indoline dyes, D102, D131, and D149, to sensitize the TiO2 electron transport layer that was employed in the Cs2AgBiBr6 perovskite solar cells (PSCs). The perovskite-indoline dye hybrid cells worked with higher power conversion efficiencies (PCEs) than the corresponding dye-sensitized solar cells and the PSC. Extended absorption resulted in a higher short-circuit current density, up to 8.24 mA cm-2, and a maximum PCE of 4.23% in the case of D149, for instance. The double perovskite worked as a p-type interlayer between the dyes and spiro-OMeTAD to convey the holes from the former to the latter, resulting in enhancement in the overall performance.

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

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.

Chlorophyll-Based Organic Heterojunction on Ti3 C2 Tx MXene Nanosheets for Efficient Hydrogen Production.

The Z-scheme process is a photoinduced electron-transfer pathway in natural oxygenic photosynthesis involving electron transport from photosystem II (PSII) to photosystem I (PSI). Inspired by the interesting Z-scheme process, herein a photocatalytic hydrogen evolution reaction (HER) employing chlorophyll (Chl) derivatives, Chl-1 and Chl-2, on the surface of Ti3 C2 Tx MXene with two-dimensional accordion-like morphology, forming Chl-1@Chl-2@Ti3 C2 Tx composite, is demonstrated. Due to the frontier molecular orbital energy alignments of Chl-1 and Chl-2, sublayer Chl-1 is a simulation of PSI, whereas upper layer Chl-2 is equivalent to PSII, and the resultant electron transport can take place from Chl-2 to Chl-1. Under the illumination of visible light (>420 nm), the HER performance of Chl-1@Chl-2@Ti3 C2 Tx photocatalyst was found to be as high as 143 µmol h-1 gcat -1 , which was substantially higher than that of photocatalysts of either Chl-1@Ti3 C2 Tx (20 µmol h-1 g-1 ) or Chl-2@Ti3 C2 Tx (15 µmol h-1 g-1 ).

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

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.

Electrochemical Behavior of Ti3 C2 Tx MXene in Environmentally Friendly Methanesulfonic Acid Electrolyte.

Two-dimensional transition metal carbides, nitrides, and carbonitrides, called MXenes, have gained much attention as electrode materials in electrochemical energy storage devices. In particular, Ti3 C2 Tx has shown outstanding performance in common sulfuric acid (H2 SO4 ) electrolyte. In this work, a more environmentally friendly alternative acidic electrolyte, methanesulfonic acid (MSA), is proposed. The energy storage performance of Ti3 C2 Tx in aqueous and neat MSA ionic liquid electrolytes is investigated. The specific capacitance of 298 F g-1 was obtained at a scan rate of 5 mV s-1 in 4 m MSA and it exhibits excellent cycle stability with retention of nearly 100 % over 10 000 cycles. This electrochemical performance is similar to that of Ti3 C2 Tx in H2 SO4 , but using a greener electrolyte. In situ X-ray diffraction analysis reveals the intercalation charge storage mechanism. Specifically, the interlayer spacing changes by up to 2.58 Šduring cycling, which is the largest reversible volume change observed in MXenes in aqueous electrolytes.