ABSTRACT
Direct observation of organic molecular nanocrystals and their evolution using electron microscopy is extremely challenging, due to their radiation sensitivity and complex structure. Here, we introduce 4D-scanning confocal electron diffraction (4D-SCED), which enables direct in situ observation of bulk heterojunction (BHJ) thin films. 4D-SCED combines confocal electron optic setup with a pixelated detector to record focused spot-like diffraction patterns with high angular resolution, using an order of magnitude lower dose than previous methods. We apply it to study an active layer in organic solar cells, namely DRCN5T:PC71BM BHJ thin films. Structural details of DRCN5T nano-crystallites oriented both in- and out-of-plane are imaged at ~5 nm resolution and dose budget of ~5 e-/Å2. We use in situ annealing to observe the growth of the donor crystals, evolution of the crystal orientation, and progressive enrichment of PC71BM at interfaces. This highly dose-efficient method opens more possibilities for studying beam sensitive soft materials.
ABSTRACT
Crystalline organic semiconducting thin films from the benchmark molecule C8-BTBT-C8 were obtained using physical vapor deposition and various solution-based methods. Utilizing atomic force microscopy and X-ray spectromicroscopy, we illustrate the influence of the underlying growth mechanism and determine the highly preparation-dependent orientation of the thiophene backbone. We observe a continuous trend for crystalline C8-BTBT-C8 thin film domains to extend into the square millimeter-range under near-equilibrium growth conditions. For such well-defined systems, electron diffraction tomography allows us to precisely determine the unit cell directly after film deposition and to reveal an 8° molecular tilt angle with respect to the surface normal. This finding is in almost perfect accordance with the values derived from near-edge X-ray absorption fine structure linear dichroism. Within this work, we shine a light on both the successes and challenges connected to the realization of potent, thiophene-based semiconducting films, paving the way toward square centimeter-sized ultrathin organic crystals and their application in organic circuitry.
ABSTRACT
The molecular self-organization of α,ω-dihexylsexithiophene (α,ω-DH6T) monolayers prepared at the solvent-water interface is investigated by complementary microscopy techniques. Our study focuses on the influence of solvents and initial droplet volume on the resulting film morphology. Long-range extended domains in the monolayer regime are detected by visible light microscopy only for toluene. Small-area electron diffraction (SAED) proves the formation of single-crystalline monolayers with structural parameters identical to the organic bulk crystals. In comparison with conventional vacuum sublimated thin films a deviant molecular orientation, derived from near-edge-X-ray absorption fine structure (NEXAFS) in combination with a lower step height measured by atomic-force-microscopy (AFM), indicates a different behaviour of the flexible terminal hexyl chains during growth in a liquid surrounding. Furthermore, a structural degradation over time is observed which is caused by residual solvent molecules that are incorporated during the transfer procedure.
ABSTRACT
The ability of a series of bridged triarylamines, so-called N-heterotriangulenes, to form multilayer-type 2D-extended films via a solution-based processing method was examined using complementary microscopic techniques. We found that the long-range order, crystallinity, and layer thickness decisively depend on the nature of the substituents attached to the polycyclic backbone. Owing to their flat core unit, compounds exhibiting a carbonyl unit at the bridge position provide a superior building block as compared to thioketone-bridged derivatives. In addition, nature and length of the peripheral substituents affect the orientation of the aromatic core unit within highly crystalline films. Hence, our results stress the significance of a suitable molecular framework and provide deeper understanding of structure formation in 2D-confined surroundings for such compounds.
ABSTRACT
Objetivo: Presentar esta anomalía de migración testicular ectópica en tres niños de diferentes edades y revisar la literatura. Pacientes y Métodos. Presentamos el caso de tres niños de diferentes edades (2 años 1 m, 5 años, 1 años 7 m) portadores de testículos ectópicos, diagnosticados y operados por el autor. Resultados. El motivo de consulta en los tres casos fue de una masa en el área de los genitales externos. El examen físico permitió comprobar que la masa era el testículo ectópico ubicados en el área perineal y en el pene, en los 2 niños que presentaron el testículo perineal tenían cada uno de ellos criptorquidia contra lateral. En ninguno de los tres pacientes hubo dificultad para realizar la orquidopexia.
Objective: Presenting this anomaly of ectopic testicular migration in three children of different ages and review literature. Patients and methods. We present the case of three children of different ages (2 years 1 m, 5 years, 1 years 7 m) carriers of ectopic testicles, diagnosed and operated by the author. Results. The reason for consultation in all three cases was of a mass in the area of the external genitalia. Examination allowed checking that the mass was ectopic testicle located in the perineal area and in the penis; the 2 children who presented the perineal testicle had each cryptochidismagainst side. In none of the three patients there difficulty to perform the orchidopexy.
