Herein the authors report the experimental application of a powerful light trapping scheme, the textured photonic crystal ͑TPC͒ backside reflector, to thin film Si solar cells. TPC combines a one-dimensional photonic crystal as a distributed Bragg reflector with a diffraction grating. Light absorption is strongly enhanced by high reflectivity and large angle diffraction, as designed with scattering matrix analysis. 5 m thick monocrystalline thin film Si solar cells integrated with TPC were fabricated through an active layer transfer technique. Measured short circuit current density J sc was increased by 19%, compared to a theoretical prediction of 28%.

Accurate measurement of interfacial properties is critical any time two materials are bonded-in composites, tooth crowns, or when biomaterials are attached to the human body. Yet, in spite of this importance, reliable methods to measure interfacial properties between dissimilar materials remain elusive. Here we present an experimental approach to quantify the interfacial fracture energy Γ i that also provides unique mechanistic insight into the interfacial debonding mechanism at the nanoscale. This approach involves deposition of an additional chromium layer (superlayer) onto a bonded system, where interface debonding is initiated by the residual tensile stress in the superlayer, and where the interface can be separated in a controlled manner and captured in situ. Contrary to earlier methods, our approach allows the entire bonded system to remain in an elastic range during the debonding process, such that Γ i can be measured accurately. We validate the method by showing that moisture has a degrading effect on the bonding between epoxy and silica, a technologically important interface. Combining in situ through scanning electron microscope images with molecular simulation, we find that the interfacial debonding mechanism is hierarchical in nature, which is initiated by the detachment of polymer chains, and that the three-dimensional covalent network of the epoxy-based polymer may directly influence water accumulation, leading to the reduction of Γ i under presence of moisture. The results may enable us to design more durable concrete composites that could be used to innovate transportation systems, create more durable buildings and bridges, and build resilient infrastructure. molecular mechanics | bimaterial systems | superlayer | energy release | biomedical I nterfaces exist whenever materials are bonded together and can be found frequently in both natural and synthetic bonded systems, for instance, the mineral-protein interfaces in animals, interfaces between different phases in composite materials, the enamel-polymer interfaces involved in dental treatment, or the cell-substrate interfaces in biomedical applications (1−7). The integrity of the interface under various environmental conditionsincluding different temperature and moisture levels-is critical to many applications (8−10). Meanwhile, because of the advancement and development in technology, a large number of bonded systems in various engineering applications are needed, possessing increasingly higher accuracy in design and manufacturing process in a very small length scale. However, currently, a robust and generally applicable methodology to quantify the fracture energy at these interfaces from a microscopic perspective is lacking.Several straightforward measurement methods for quantifying the interfacial fracture energy on large specimens, such as direct peel/shear specimen (11, 12), Brazilian disk specimen (13), and sandwiched beam specimen (14, 15), have been reported. However, it has been difficult to directly measure this parameter for microscale...

Dark-field microscopy is a standard imaging technique widely employed in biology that provides high image contrast for a broad range of unstained specimens 1. Unlike bright-field microscopy, it accentuates high spatial frequencies and can therefore be used to emphasize and resolve small features. However, the use of dark-field microscopy for reliable analysis of blood cells, bacteria, algae, and other marine organisms often requires specialized, bulky microscope systems, and expensive additional components, such as dark-field-compatible objectives or condensers 2,3. Here, we propose to simplify and downsize dark-field microscopy equipment by generating the high-angle illumination cone required for dark field microscopy directly within the sample substrate. We introduce a luminescent photonic substrate with a controlled angular emission profile and demonstrate its ability to generate high-contrast dark-field images of micrometre-sized living organisms using standard optical microscopy equipment. This new type of substrate forms the basis for miniaturized lab-on-chip dark-field imaging devices, compatible with simple and compact light microscopes.

We have demonstrated a new photonic structure to achieve strong optical coupling between nanoparticle and photonic molecule by utilizing a notched micro ring resonators. By creating a notch in the ring resonator and putting a nanoparticle inside the notch, large spectral shifts and splittings at nm scale can be achieved, compared to only pm scale observed by fiber tip evanescently coupled to the surface of microsphere, thereby significantly lowered the quality factor requirement for single nanoparticle detection. The ability for sorting the type of nanoparticles due to very different mode shift and splitting behavior of dielectric and metallic nanoparticles is also emphasized. *