Polarization-Type Potential-Induced Degradation in Front-Emitter p-Type and n-Type Crystalline Silicon Solar Cells.

For SiO2 layers underneath the SiN x antireflection/passivation layers of front-emitter p-type c-Si solar cells, this paper presents an investigation into their effects on polarization-type potential-induced degradation (PID), in addition to a comparison of polarization-type PID behavior in front-emitter p-type c-Si cells and front-emitter n-type c-Si cells. After PID tests with a bias of +1000 V, p-type c-Si cells without SiO2 layers underneath the SiN x layers showed no degradation, although p-type c-Si cells with approx. 10 nm thick SiO2 layers showed polarization-type PID, which is characterized by a reduction of the short-circuit current density and the open-circuit voltage. This result implies that highly insulating layers such as SiO2 layers play an important role in the occurrence of polarization-type PID. Comparison of polarization-type PID in p-type and n-type c-Si cells with SiO2 layers indicated that degradation in the n-type cells is greater and saturates in a shorter time than in the p-type cells. This result is consistent with an earlier proposed model based on the assumption that polarization-type PID is caused by charge accumulation at K centers in SiN x layers. The findings described herein are crucially important for elucidating polarization-type PID and verifying the degradation model.

Biological activity of peptide-conjugated polyion complex matrices consisting of alginate and chitosan.

Peptide-conjugated polysaccharide matrices using bioactive laminin-derived peptides are useful biomaterials for tissue and cell engineering. Here, we demonstrate an easy handling preparation method for peptide-polysaccharide matrices using polyion complex with both alginate and chitosan. First, aldehyde-alginate was synthesized by oxidization of alginate using NaIO4 , and then, reacted with Cys-peptides. Next, the peptide-alginate solution was added to a chitosan-coated plate, and the peptide-polyion complex matrices (peptide-PCMs) were prepared. The peptide-PCMs using an integrin αvß3-binding peptide (A99a: ALRGDN, mouse laminin α1 chain 1145-1150) and an integrin α2ß1-binding peptide (EF1XmR: RLQLQEGRLHFXFD, X = Nle, mouse laminin α1 chain 2751-2763) showed strong cell attachment activity in a dose-dependent manner. When we examined the effect of various spacers on the biological activity of A99a-PCM, hydrophobic and long spacers enhanced the cell attachment activity. Further, the A99a-PCM with the spacers strongly promoted neurite outgrowth. The polyion complex method is an easy way to obtain insolubilized matrix and is widely applicable for various polysaccharides. The peptide-PCM is useful as a biomaterial for cell and tissue engineering.

Mixed Fibronectin-Derived Peptides Conjugated to a Chitosan Matrix Effectively Promotes Biological Activities through Integrins, α4ß1, α5ß1, αvß3, and Syndecan.

Mimicking the biological function of the extracellular matrix is an approach to developing cell adhesive biomaterials. The RGD peptide, derived from fibronectin (Fn), mainly binds to integrin αvß3 and has been widely used as a cell adhesive peptide on various biomaterials. However, cell adhesion to Fn is thought to be mediated by several integrin subtypes and syndecans. In this study, we synthesized an RGD-containing peptide (FIB1) and four integrin α4ß1-binding-related motif-containing peptides (LDV, IDAPS, KLDAPT, and PRARI) and constructed peptide-chitosan matrices. The FIB1-chitosan matrix promoted human dermal fibroblast (HDF) attachment, and the C-terminal elongated PRARI (ePRARI-C)-conjugated chitosan matrix significantly promoted HDF attachment through integrin α4ß1 and syndecan binding. Next, we constructed a mixed ePRARI-C- and FIB1-chitosan matrix to develop a Fn mimetic biomaterial. The mixed ePRARI-C/FIB1-chitosan matrix promoted significantly better cell attachment and neurite outgrowth compared to those of either ePRARI-C- or FIB1-chitosan matrices. HDF adhesion to the ePRARI-C/FIB1-chitosan matrix was mediated by integrin, α4ß1, α5ß1, and αvß3, similar to HDF adhesion to Fn. These data suggest that an ePRARI-C/FIB1-chitosan matrix can be used as a tool to analyze the multiple functions of Fn and can serve as a Fn-mimetic biomaterial.