The dyes in dye-sensitized solar cells (DSSCs) require one or more chemical substituents that can act as an anchor, enabling their adsorption onto a metal oxide substrate. This adsorption provides a means for electron injection, which is the process that initiates the electrical circuit in a DSSC. Understanding the structure of various DSSC anchors and the search for new anchors are critical factors for the development of improved DSSCs. Traditionally, carboxylic acid and cyanoacrylic acid groups are employed as dye anchors in DSSCs. In recent years, novel anchor groups have emerged, which make a larger pool of materials available for DSSC dyes, and their associated physical and chemical characteristics offer interesting effects at the interface between dye and metal oxide. This review focuses especially on the structural aspects of these novel dye anchors for TiO2-based DSSCs, including pyridine, phosphonic acid, tetracyanate, perylene dicarboxylic acid anhydride, 2-hydroxylbenzonitrile, 8-hydroxylquinoline, pyridine-N-oxide, hydroxylpyridium, catechol, hydroxamate, sulfonic acid, acetylacetanate, boronic acid, nitro, tetrazole, rhodanine, and salicylic acid substituents. We anticipate that further exploration and understanding of these new types of anchoring groups for TiO2 substrates will not only contribute to the development of advanced DSSCs, but also of quantum dot-sensitized solar cells, water splitting systems, and other self-assembled monolayer-based technologies.

Dye aggregation dictates structural and optoelectronic properties of photoelectrodes in dye-sensitized solar cells (DSSCs), thereby playing an essential role in their photovoltaic performance.

No abstract

A facile and green mechanosynthesis strategy free of solvent and high reaction temperature was developed to fabricate highly emissive cesium lead halide perovskite (CsPbX) quantum dots (QDs). Their composition can be adjusted conveniently simply through mechanically milling/grinding stoichiometric combinations of raw reagents, thereby introducing a broad luminescence tunability of the product with adjustable wavelength, line width, and photoluminescence quantum yield. Desired CsPbX QDs "library" can thus be readily constructed in a way like assembling Lego building blocks. Hence, the method offered new avenues in the preparation of multicomponent cocrystals, adding one appealing apparatus to the tool box of perovskite-type QDs synthesis. Intriguingly, photoinduced dynamic study revealed the hole-transfer process of the as-prepared QDs toward electron donors, indicative of their potential in charge-transfer-based applications such as light-harvesting devices and photocatalysis.

No abstract

Lead halide perovskites have witnessed significant progress in low-cost and high-efficiency photovoltaics, with a rapid increase in photovoltaic efficiencies from 3.8% to a certified record of 25.2% in the past decade. [1-4] However, the viability and practical scale-up implementation are limited by the stability and toxicity of the lead halide perovskites. [5,6] To circumvent these two

The relationship between the molecular structures of a series of azo dyes and their operational performance when applied to dye-sensitized solar cells (DSSCs) is probed via experimental and computational analysis. Seven azo dyes, with three different donating groups (dimethylamino, diethylamino, and dipropylamino) and carboxylic acid anchoring positions (ortho-, meta-, and para-substituted phenyl rings) are studied. Single-crystal X-ray diffraction is employed in order to analyze the effects of conformation and quantify the contribution of quinoidal resonance forms to the intramolecular charge transfer (ICT), which controls their intrinsic photovoltaic potential from an electronic standpoint. Harmonic oscillator stabilization energy (HOSE) calculations indicate that the para- and ortho-azo dyes exhibit potential for DSSC application. However, from a geometrical standpoint, the crystal structure data, proton nuclear magnetic resonance spectroscopy (1H NMR), and density functional theory (DFT) all indicate that intramolecular hydrogen bonds form in ortho-dyes within both solid and solution states, impeding their intrinsic ICT-based photovoltaic potential, and offering insights into the photostability of azo dyes and the dye···TiO2 anchoring mechanism in DSSCs. Donor effects are manifested in the packing mode and molecular planarity revealed by X-ray crystallography and in the UV/vis absorption spectra. DFT and time-dependent density functional theory (TDDFT) were performed to understand the electronic and optical properties of these azo dyes; these calculations compare well with experimental findings. Operational tests of DSSCs, functionalized by these azo dyes, show that the carboxylic acid anchoring position plays a crucial role in DSSC performance, while donating groups offer a much less obvious effect on the overall DSSC device efficiency.

With efficiencies exceeding 20% and low production costs, lead halide perovskite solar cells (PSCs) have become potential candidates for future commercial applications. However, there are serious concerns about their long-term stability and environmental friendliness, heavily related to their commercial viability. Herein, we present a theoretical investigation based on the ab initio molecular dynamics (AIMD) simulations and the first-principles density functional theory (DFT) calculations to investigate the effects of sunlight and moisture on the structures and properties of MAPbI3 perovskites. AIMD simulations have been performed to simulate the impact of a few water molecules on the structures of MAPbI3 surfaces terminated in three different ways. The evolution of geometric and electronic structures as well as the absorption spectra has been shown. It is found that the PbI2-terminated surface is the most stable while both the MAI-terminated and PbI2-defective surfaces undergo structural reconstruction, leading to the formation of hydrated compounds in a humid environment. The moisture-induced weakening of photoabsorption is closely related to the formation of hydrated species, and the hydrated crystals MAPbI3·H2O and MA4PbI6·2H2O scarcely absorb the visible light. The electronic excitation in the bare and water-absorbed MAPbI3 nanoparticles tends to weaken Pb-I bonds, especially those around water molecules, and the maximal decrease of photoexcitation-induced bond order can reach up to 20% in the excited state in which the water molecules are involved in the electronic excitation, indicating the accelerated decomposition of perovskites in the presence of sunlight and moisture. This work is valuable for understanding the mechanism of chemical or photochemical instability of MAPbI3 perovskites in the presence of moisture.