Revisiting Solvent Additives for the Fabrication of Polymer:Fullerene Solar Cells: Exploring a Series of Benzaldehydes

The power conversion efficiencies of organic solar cells delicately depend on the morphology of the light-harvesting bulk heterojunctions (BHJ). Upon deposition from solution, the formation of tailored bicontinuous networks of polymers and fullerenes is often achieved using combinations of solvents and solvent additives. Common wisdom infers that best solar cell performances are achieved when the solvent additives exhibit excellent fullerene solubility. Herein, this concept is revisited based on the investigation of a series of structurally similar, substituted benzaldehydes. It is concluded that the solvent additives do not only have to feature the commonly accepted good fullerene solubility, but must also exhibit lowest polymer solubility to suppress liquid–liquid demixing and hence achieve best solar cell performance. Thus, this study adds an important item to the list of selection criteria of solvent additives toward the production of polymer:fullerene solar cells with optimized power conversion efficiencies. The microscopic picture of the resulting domain configurations within the light-harvesting layers is developed around comprehensive multiscale investigations of the BHJ morphology, using atomic force microscopy, scanning transmission electron microscopy, and nano-infrared microscopy. The latter is operated in two complementary modes, one of which is more bulk sensitive, whereas the other mode is surface sensitive

Lack of evidence for a causal role of CALR3 in monogenic cardiomyopathy

The pathogenicity of previously published disease-associated genes and variants is sometimes questionable. Large-scale, population-based sequencing studies have uncovered numerous false assignments of pathogenicity. Misinterpretation of sequence variants may have serious implications for the patients and families involved, as genetic test results are increasingly being used in medical decision making. In this study, we assessed the role of the calreticulin-3 gene (CALR3) in cardiomyopathy. CALR3 has been included in several cardiomyopathy gene panels worldwide. Its inclusion is based on a single publication describing two missense variants in patients with hypertrophic cardiomyopathy. In our national cardiomyopathy cohort (n = 6154), we identified 17 unique, rare heterozygous CALR3 variants in 48 probands. Overall, our patient cohort contained a significantly higher number of rare CALR3 variants compared to the ExAC population (p = 0.0036). However, after removing a potential Dutch founder variant, no statistically significant difference was found (p = 0.89). In nine probands, the CALR3 variant was accompanied by a disease-causing variant in another, well-known cardiomyopathy gene. In three families, the CALR3 variant did not segregate with the disease. Furthermore, we could not demonstrate calreticulin-3 protein expression in myocardial tissues at various ages. On the basis of these findings, it seems highly questionable that variants in CALR3 are a monogenic cause of cardiomyopathy

Dendrimer-cyclodextrin assemblies as stabilizers for gold and platinum nanoparticles

Aqueous assemblies of adamantyl-derivatized poly(propylene imine) (PPI) dendrimers and B-cyclodextrin (B-CD) have been used as nanoreactors in the preparation of gold and platinum nanoparticles in water. These particles have been formed by the reduction of aurate or platinate anions in the presence of the generation 4 (4·(B-CD)32) and 5 ( 5·(B-CD)40) assemblies. Lower generation assemblies did not provide stable nanoparticles. A kinetic model is proposed in which the particles form inside the dendrimer assemblies owing to preferred nucleation as a result of the electrostatic attraction between the polycationic core and the metallate anions. The persistent shape of the adamantyl-derivatized dendrimers and the dense shell of adamantyl-B-CD complexes provide a kinetic barrier for nanoparticle escape thus prolonging their lifetime. Exchange of the dendrimers for a cationic disulfide provided stable, water-soluble metal nanoparticles without change of their size distribution.\u

Short-circuit prevention strategies in organic light-emitting diodes and solar cells

Short-circuit prevention and repair strategies are essential to allow for upscaled production of organic electronic devices based on thin-film production technology. Occurrence of short circuits is a consequence of manufacturing imperfections and particle contamination. After giving a concise review of short-circuit prevention methods for organic thin-film devices in the open literature of the past decade, this overview article summarizes our recent work on short-circuit prevention in organic light-emitting diodes and organic solar cells by chemical oxidation methods. Our main strategy is based on self-aligned disruption of the conductivity of exposed areas of the typically applied hole transport material poly(3,4-ethylenedioxythiophene): poly (styrene sulfonate) by aqueous sodium hypochlorite, prior to cathode deposition. The ten orders of magnitude decrease in local conductivity obtained proves sufficient to let deliberately flawed devices operate at pristine performance levels. We next show that in the case of organic solar cells based on a lithium fluoride/aluminium cathode the shunting junctions can be made sufficiently resistive to allow for near unflawed operation, without applying wet treatment

Probing the interactions of calix[4]arene-based amphiphiles and cyclodextrins in water

The surfactant behavior of the water-soluble calix[4]arene 1, which has carboxylate groups at the upper rim and two phenyl groups at the lower rim, and its complexation to -cyclodextrin were studied. The critical micelle concentration (cmc) of 1 and of tetrapropoxycalix[4]arenetetracarboxylate 2 are 35 and 650 M, respectively. The stabilities of the 1:1 inclusion complexes of -cyclodextrin with 1 and 2 are 1.3 × 104 and 1.5 × 103 M-1, respectively. The stability of the former complex was derived from a calorimetric titration under conditions where 1 is largely micellized. A minimization routine is described for determining the heat contributions of demicellization and complexation. The association of 1 to -cyclodextrin is enthalpy-driven, which, together with the high K value and the 1:1 binding stoichiometry, indicates that both pendant phenyl rings of 1 are included in the y-cyclodextrin cavity

Complexation of porphyrin-appended guests by calix[4]arene-appended cyclodextrins

A calix[4]arene based β-cyclodextrin dimerand tetramer (1 and2, Figure 1) were synthesized by covalentattachment of amono(2-O-xylylamino)-β-cyclodextrinderivative to calix[4]areneplatforms, bi- or tetrafunctionalized withcarboxylic acid groups at their upperrims. The complexation of porphyrin-basedguest molecules by these hosts inwater was studied using microcalorimetry.Tetrakis(4-phenylsulfonato)porphyrin(TsPP) binds to 2 in a 1 : 2 (host : guest)fashion with enhanced bindingstrength (K1 = 6.6 × 106 M -1) ascompared to the monomeric TsPP–CDinteraction (K = 8.8 × 105 M -1). Thisenhancement is attributed tothe involvement of two cyclodextrin units in theaccommodation of one TsPP guest.Increase of the number of 4-sulfonatophenyl siteson the guest by generating theμ-oxo-dimer of the iron(III) complex of TsPPled to further increase of thebinding strength owing to participation of threeβ-cyclodextrin cavities of2 (K = 1.5 × 107 M -1). The geometricincompatibility betweenhost and guest, stemming from the fact that both TsPPand its μ-oxo-dimer arefairly small compared to the multi-cyclodextrin hosts,probably explains why theenhancement is still moderate. A much more pronouncedincrease in complexationstrength was achieved with p- and m-pyridylporphyrinextended withp-tert-butylbenzyl guest sites. Theseguests are large enough to accommodatethree to four β-cyclodextrin units. The bettermatch in size between host and guestgave association constants up 108 and 109 M -1for the β-cyclodextrindimer and tetramer, respectively. In fact, the 1 : 1complex betweentetrakis(p-tert-butylbenzyl)-p-pyridylporphyrinand 2(K = 5 × 109 M -1) is the strongestreported for cyclodextrin–porphyrininteractions