Search results for "Kite"
showing 10 items of 1123 documents
Dibenzoquinquethiophene- and Dibenzosexithiophene-Based Hole-Transporting Materials for Perovskite Solar Cells
2018
Fused oligothiophene-based π-conjugated organic derivatives have been widely used in electronic devices. In particular, two-dimensional (2D) heteroarenes offer the possibility of broadening the scope by extending the π-conjugated framework, which endows enhanced charge transport properties due to the potential intermolecular π–π stacking. Here, the synthesis and characterization of two new small-molecule hole-transporting materials (HTMs) for perovskite solar cells (PSCs) are reported. The newly custom-made compounds are based on dibenzoquinquethiophene (DBQT) and dibenzosexithiophene (DBST) cores, which are covalently linked to triphenylamine moieties to successfully afford the four-armed …
Tuning the Optical Absorption of Sn-, Ge-, and Zn-Substituted Cs2AgBiBr6 Double Perovskites: Structural and Electronic Effects
2021
Lead-free halide double perovskites (DPs) are highly tunable materials in terms of chemical composition and optical properties. One of the most widely reported DPs is Cs2AgBiBr6, which is envisaged as a promising absorber for photovoltaics. Nevertheless, its bandgap (around 1.9−2.3 eV) remains too large for common tandem solar cells. In this work, we report the mechanochemical synthesis of Sn-, Ge-, and Zn-substituted Cs2AgBiBr6 in powder form; their bandgaps reach 1.55, 1.80, and 2.02 eV, respectively. These differences are rationalized through density functional theory calculations, demonstrating combined electronic and structural (disorder) effects introduced by the divalent metal-cation…
Colloids of naked CH 3 NH 3 PbBr 3 Perovskite Nanoparticles: Synthesis, Ssability, and thin solid film deposition
2018
A novel preparation of lead halide, CH3NH3PbBr3, perovskite nanoparticle solid films from colloidal "naked" nanoparticles, that is, dispersible nanoparticles without any surfactant, is reported. The colloids are obtained by simply adding potassium ions, whose counterions are both more lipophilic and less coordinating than bromide ions, to the perovskite precursor solutions (CH3NH3Br/PbBr2 in dimethylformamide) following the reprecipitation strategy. The naked nanoparticles exhibit a low tendency to aggregate in solution, and they effectively self-assembled on a substrate by centrifugation of the colloid, leading to homogeneous nanoparticle solid films with arbitrary thickness. These results…
Heteroatom Effect on Star-Shaped Hole-Transporting Materials for Perovskite Solar Cells
2018
The Intrinsic Defects, Disordering, and Structural Stability of BaxSr1–xCoyFe1–yO3−δ Perovskite Solid Solutions
2012
First principles density functional theory modeling of point defects and structural disordering in BaxSr1–xCoyFe1–yO3−δ (BSCF) perovskites reveals that the material tends to decompose at low temperatures into a mixture of cubic and hexagonal perovskite and/or oxide phases. Special attention is paid to elucidating the effects of oxygen nonstoichiometry on cubic and hexagonal phase stability, decomposition energies, and oxygen vacancy formation energies. The observed lattice instability is likely to negate the advantages of the fast oxygen transport chemistry and impede the applicability of BSCF in solid oxide fuel cells and oxygen separation ceramic membranes. The general methodology present…
Hole-Transporting Materials for Perovskite Solar Cells Employing an Anthradithiophene Core
2021
A decade after the report of the first efficient perovskite-based solar cell, development of novel hole-transporting materials (HTMs) is still one of the main topics in this research field. Two of the main advance vectors of this topic lie in obtaining materials with enhanced hole-extracting capability and in easing their synthetic cost. The use of anthra[1,9-bc:5,10-b'c']dithiophene (ADT) as a flat π-conjugated frame for bearing arylamine electroactive moieties allows obtaining two novel highly efficient HTMs from very cheap precursors. The solar cells fabricated making use of the mixed composition (FAPbI3)0.85(MAPbBr3)0.15 perovskite and the novel ADT-based HTMs show power conversion effi…
Use of Hydrogen Molybdenum Bronze in Vacuum‐Deposited Perovskite Solar Cells
2019
Herein, the dehydration of a hydrogen molybdenum bronze (HYMoO3), converting it to molybdenum oxide (MoOX), is explored toward the development of perovskite solar cells (PSCs) for the first time. H0.11MoO3 bronze is synthesized, characterized, and deposited on indium tin oxide (ITO) under different concentrations and annealing conditions for in situ conversion into MoOX with appropriate oxygen vacancies. Vacuum‐deposited PSCs are fabricated using the as‐produced MoOX hole injection layers, achieving a power conversion efficiency of 17.3% (average) for the optimal device. The latter has its stability and reproducibility tested, proving the robustness and affordability of the developed hole t…
Quantifying the Composition of Methylammonium Lead Iodide Perovskite Thin Films with Infrared Spectroscopy
2019
Lead halide perovskites (ABX3) are generally formed from a reaction of the lead halide salt (BX2) with the halide salt of the A cation (AX). The effects of varying film compositions as result of non-stoichiometric precursor ratios on electronic properties of halide perovskites are currently under debate. It is imperative, but experimentally challenging, to determine the chemical composition of thin films as a function of precursor ratio for a full understanding of the effect. Herein we report a precise quantification of the methylammonium (MA) content in differently fabricated films of MAPbI3 via infrared (IR) spectroscopy. We compare the thin film data to the first high quality dielectric …
External quantum efficiency measurements used to study the stability of differently deposited perovskite solar cells
2020
The instability exhibited by perovskite solar cells when exposed to the environment under illumination is one of the major obstacles for the entry of perovskite technology in the photovoltaic market. In this work, we use the external quantum efficiency (EQE) technique to study the photoinduced degradation of two types of solar cells having CH3NH3PbI3 as an absorber layer: one deposited by spin coating with an n-i-p architecture and the other deposited by evaporation with an inverted p-i-n structure. We also study the effect of different encapsulants to protect the cells against atmospheric agents. We find that EQE provides information regarding the areas of the cell most susceptible to degr…
Radiation Induced Defects in Yttrium Aluminium Perovskite
2000
The yttrium aluminium perovskite single crystals YAlO3 (YAP) doped with rare -earth ions belong to the most prospective materials of solid-state laser engineering. Laser based of YAlO3 crystals have the advantage in comparison with yttrium aluminium garnet (YAG). The main of them consists in anisotropy of optical properties [1], which are stipulated by the low symmetry of orthoaluminate crystals. Continuos wave (CW) laser action at 549.6 nm was achieved in 1% Er:YAP crystal at below 77 K [2]. The YAP:Nd allows to obtain a CW generation at 1079 nm, 1340 nm and 1440 nm [3, 4]. It is known, that the color center can completely suppress laser generation in the crystal.