Luminescent crystals and manufacturing thereof

The present invention relates to the field of luminescent crystals (LCs), and more specifically to Quantum Dots (QDs) of formula A1aM2bXc, wherein the substituents are as defined in the specification. The invention provides methods of manufacturing such luminescent crystals, particularly by dispersing suitable starting materials in the presence of a liquid and by the aid of milling balls; to compositions comprising luminescent crystals and to electronic devices, decorative coatings; and to components comprising luminescent crystals.</p

Solid polymer composition

The present invention relates in a first aspect to a solid polymer component comprising luminescent crystals of 3-500 nm size, surfactant and a hardened/cured polymer. In a second aspect of the invention, a luminescent component comprises a first element comprising the solid polymer component according to the first aspect and an encapsulation enclosing the first element. In a third aspect of the invention, a luminescent component comprises a first film comprising the solid polymer composition of the first aspect. A fourth aspect of the invention relates to a light emitting device comprising the luminescent component according to the second or third aspect of the invention and a light source.</p

Opto-electronics of PbS quantum dot and narrow bandgap polymer blends

Here we report on the interaction between the narrow bandgap polymer [2,6-(4,4-bis(2-ethylhexyl)-4H-cyclopenta-[2,1-b;3,4-b]dithiophene)-alt-4,7-(2,1,3-benzothiadiazole)] (PCPDTBT) and lead sulphide (PbS) colloidal quantum dots (CQDs) upon photoexcitation. We show that the presence of both materials in a blend leads to a significant reduction of photoluminescence (PL) lifetime of the polymer. This observation is attributed, supported by transient absorption (TA) data, to an efficient electron transfer towards the QDs for excitons generated on the polymer. Furthermore, the ligand capping the QD surface exhibits a great impact on the dynamics of the PL, with the long-chain oleic acid (OA) largely suppressing any kind of interaction. By means of external quantum efficiency (EQE) measurements we find evidence that both components give rise to a contribution to the photocurrent, making this an interesting blend for future applications in hybrid organic-inorganic solar cells.</p

Organic-inorganic hybrid solution-processed H2-evolving photocathodes

Here we report for the first time an H2-evolving photocathode fabricated by a solution-processed organic inorganic hybrid composed of CdSe and P3HT. The CdSe:P3HT (10:1 (w/w)) hybrid bulk heterojunction treated with 1,2-ethanedithiol (EDT) showed efficient water reduction and hydrogen generation. A photocurrent of -1.24 mA/cm(2) at 0 V versus reversible hydrogen electrode (V-RHE), EQE of 15%, and an unprecedented V-oc of 0.85 V-RHE under illumination of AM1.5G (100 mW/cm(2)) in mild electrolyte were observed. Time-resolved photoluminescence (TRPL), internal quantum efficiency (IQE), and transient photocurrent measurements were carried out to clarify the carrier dynamics of the hybrids. The exciton lifetime of CdSe was reduced by one order of magnitude in the hybrid blend, which is a sign of the fast charge separation upon illumination. By comparing the current magnitude of the solid-state devices and water-splitting devices made with identical active layers, we found that the interfaces of the water-splitting devices limit the device performance. The electron/hole transport properties investigated by comparing IQE spectra upon front- and back-side illumination evidenced balanced electron/hole transport. The Faradaic efficiency is 80-100% for the hybrid photocathodes with Pt catalysts and similar to 70% for the one without Pt catalysts

Understanding the Surface Chemistry of SnO₂ Nanoparticles for High Performance and Stable Organic Solar Cells

In organic solar cells, the interfaces between the photoactive layer and the transport layers are critical in determining not only the efficiency but also their stability. When solution-processed metal oxides are employed as the electron transport layer, the presence of surface defects can downgrade the charge extraction, lowering the photovoltaic parameters. Thus, understanding the origin of these defects is essential to prevent their detrimental effects. Herein, it is shown that a widely reported and commercially available colloidal SnO2 dispersion leads to suboptimal interfaces with the organic layer, as evidenced by the s-shaped J–V curves and poor stability. By investigating the SnO2 surface chemistry, the presence of potassium ions as stabilizing ligands is identified. By removing them with a simple washing with deionized water, the s-shape is removed and the short-circuit current is improved. It is tested for two prototypical blends, TPD-3F:IT-4F and PM6:L8:BO, and for both the power conversion efficiency is improved up to 12.82% and 16.26%, from 11.06% and 15.17% obtained with the pristine SnO2, respectively. More strikingly, the stability is strongly correlated with the surface ions concentration, and these improved devices maintain ≈87% and ≈85% of their initial efficiency after 100 h of illumination for TPD-3F:IT-4F and PM6:L8:BO, respectively.</p

Free carrier generation and recombination in PbS quantum dot solar cells

Time Delayed Collection Field and Bias Assisted Charge Extraction (BACE) experiments are used to investigate the charge carrier dynamics in PbS colloidal quantum dot solar cells. We find that the free charge carrier creation is slightly field dependent, thus providing an upper limit to the fill factor. The BACE measurements reveal a rather high effective mobility of 2 x 10(-3) cm(2)/Vs, meaning that charge extraction is efficient. On the other hand, a rather high steady state non-geminate recombination coefficient of 3 x 10(-10) cm(3)/s is measured. We, therefore, propose a rapid free charge recombination to constitute the main origin for the limited efficiency of the PbS colloidal quantum dots cells. (C) 2016 AIP Publishing LLC

Tuning the Energetic Landscape of Ruddlesden-Popper Perovskite Films for Efficient Solar Cells

Ruddlesden-Popper perovskite films deposited with different methods show very diverse phase segregation and composition. When DMSO is used as solvent, the conventional method based on spin-coating and annealing produces very poor devices, whereas the vacuum-assisted method proposed here allows obtaining devices with efficiency up to 14.14%. The conventional method gives rise to a three-dimensional (3D)-like phase on the top of the film but dominant n = 2 phase with large domains (∼40 μm) at the bottom of the film. These n = 2 domains are oriented with their inorganic slabs parallel to the substrate and inhibit the charge transport in the vertical direction. Consequently, severe monomolecular and bimolecular charge recombination occurs in the solar cells. Conversely, the vacuum-assisted method yields films with a 3D-like phase dominant throughout their entire thickness and only a small amount of n ≤ 2 domains of limited dimensions (∼3 μm) at the bottom, which facilitate charge transport and reduce charge recombination

Tuning the Energetic Landscape of Ruddlesden-Popper Perovskite Films for Efficient Solar Cells

Ruddlesden-Popper perovskite films deposited with different methods show very diverse phase segregation and composition. When DMSO is used as solvent, the conventional method based on spin-coating and annealing produces very poor devices, whereas the vacuum-assisted method proposed here allows obtaining devices with efficiency up to 14.14%. The conventional method gives rise to a three-dimensional (3D)-like phase on the top of the film but dominant n = 2 phase with large domains (∼40 μm) at the bottom of the film. These n = 2 domains are oriented with their inorganic slabs parallel to the substrate and inhibit the charge transport in the vertical direction. Consequently, severe monomolecular and bimolecular charge recombination occurs in the solar cells. Conversely, the vacuum-assisted method yields films with a 3D-like phase dominant throughout their entire thickness and only a small amount of n ≤ 2 domains of limited dimensions (∼3 μm) at the bottom, which facilitate charge transport and reduce charge recombination.</p