Towards light-trapping free amorphous Si only multi-junction solar cells

We propose a thin film solar cell structure that enables ultrathin film absorber application and single material multi-junction structure. This proposal is targeting amorphous Si only multi-junction solar cells on a patterned transparent electrode, which might perform high light harvesting efficiency and high output voltage at the same time. In addition, photon management of this proposed structure does not rely on traditional light trapping scheme but rather on lateral collection scheme with sidewall solar cells. To implement the proposed solar cells, a suitable process sequence is suggested, where a challenging node separation process between sidewall solar cells is included. In this work, we present a-Si solar cell on patterned TCO without node separation. We found the signature of absorption path elongation by sidewall solar cells, which is one of the essential principles of our proposed solar cell. This proposal would provide a promising route to a high performance and low cost a-Si only photovoltaics

Detection of the acupuncture points in skin by differential path-length spectroscopy

An optical fiber-based diagnostic system was developed to detect the acupuncture points (Bonghan Corpuscle) with small depth in human skin. A split fiber with 600 micrometer diameter was used in contact with the skin to deliver and detect the light to yield backscattered signal, which took information from both small and deep layers. The effect of backscattered signal from deep layer of skin was removed by another single fiber with the same diameter as the split fiber. Both fibers were arranged as close as possible to each other to detect the optical properties of tissue in a very small volume. The optical properties of the acupuncture point and its surrounding tissue in the skin were measured separately in the visible wavelength range (400–700nm), and significant difference was found between them. To control the consistency and reproduction of the experimental conditions of the fiber on the skin, a precise pressure sensor was employed

Stress-strain curves of flip-chip solder balls based on finite-element modeling of thermal displacements measured by electronic speckle pattern interferometry

Electronic speckle pattern interferometry (ESPI) was applied to noncontact, real-time evaluation of thermal deformation in a flip-chip solder joint. To measure the deformation of such tiny components as the solder balls in the flip-chip, the spatial resolution of ESPI was increased to submicron scale by magnifying the areas studied. Experimental-computational procedures were developed to obtain stress-strain curves for solder balls in the flip-chip based on finite-element modeling (FEM) of in-plane ESPI thermal displacement data. The stress-strain curve obtained for the flip-chip solder was compared with those for bulk solder. The microstructure was also studied to clarify the stress-strain curve results.open2