High Open-Circuit Voltage Wide-Bandgap Perovskite Solar Cell with Interface Dipole Layer.

Wide-bandgap perovskite solar cells (PSCs) with high open-circuit voltage (Voc) represent a compelling and emerging technological advancement in high-performing perovskite-based tandem solar cells. Interfacial engineering is an effective strategy to enhance Voc in PSCs by tailoring the energy level alignments between the constituent layers. Herein, n-type quinoxaline-phosphine oxide-based small molecules with strong dipole moments is designed and introduce them as effective cathode interfacial layers. Their strong dipole effect leads to appropriate energy level alignment by tuning the work function of the Ag electrode to form an ohmic contact and enhance the built-in potential within the device, thereby improving charge-carrier transport and mitigating charge recombination. The organic interfacial layer-modified wide-bandgap PSCs exhibit a high Voc of 1.31 V (deficit of <0.44 V) and a power conversion efficiency (PCE) of 20.3%, significantly improved from the device without an interface dipole layer (Voc of 1.26 V and PCE of 16.7%). Furthermore, the hydrophobic characteristics of the small molecules contribute to improved device stability, retaining 95% of the initial PCE after 500 h in ambient air.

Fate of E-cadherin in early RPE cultures: transient accumulation of truncated peptides at nonjunctional sites.

PURPOSE: E-cadherin is known to accumulate variably and slowly at junctions of cultured human RPE cells. The intent of this investigation was to determine what limits E-cadherin protein accumulation in RPE cells by analyzing cultures at early postplating intervals when junctions of the dominant cadherin (N-cadherin) are first forming. METHODS: RPE cell lines hTERT-RPE1 and ARPE-19 and RPE cultures established from human donors were analyzed within 48 hours after plating for E-cadherin gene and protein expression (by RT-PCR and Western blotting, respectively) and for protein distribution (by immunofluorescence and immuno-electron microscopy), including codistribution with markers for organelles. Cell surface localization was analyzed by biotinylation and trypsin cleavage of extracellular cadherin domains. RESULTS: The E-cadherin gene was constitutively expressed by RPE cultures, but the protein did not accumulate substantially in early RPE cultures. Instead small amounts of newly synthesized E-cadherin were detectable only transiently, peaking within a few hours after plating, at which time the protein was in the form of peptides of variable size rather the predicted 120-kDa molecular mass. Immunoreactive E-cadherin peptides did not traffic to the cell surface and localize to junctions. Rather they codistributed with several organelles including the endoplasmic reticulum (ER; but not the Golgi), sites of protein degradation (proteasomes, lysosomes, and autophagosomes) and unusual compartments (centrosomes and apposed to subdomains of the mitochondrial network). CONCLUSIONS: The results suggest that in RPE cells posttranscriptional mechanisms involving altered protein processing and rapid turnover exist to limit E-cadherin accumulation. The consequence may be to limit E-cadherin-specific inductive properties in the RPE, a cell type in which N-cadherin is the normal dominant cadherin.

Cell phenotype in normal epithelial cell lines with high endogenous N-cadherin: comparison of RPE to an MDCK subclone.

PURPOSE: Unlike most monolayer epithelial cells, cultured RPE are competent to form a zonular adhesion of N- rather than E-cadherin. To determine whether other normal epithelial cells do likewise, cells with high endogenous N-cadherin were cloned from the typically E-cadherin dominant epithelial line Madin-Darby canine kidney cells (MDCK) to analyze cell and junction phenotype in the presence of N-cadherin. METHODS: A MDCK subclonal line, clone-YH, was selected for high endogenous N-cadherin and was compared with the RPE line hTERT-RPE1 with regard to cell phenotype, cadherin gene expression and cadherin protein distribution, glycosylation state, and catenin complex composition. RESULTS: In early cultures, hTERT-RPE1 cells are moderately epithelioid with junctional N-cadherin, but clone-YH cells are initially highly fusiform with N-cadherin in multiple sites. With time, N-cadherin in clone-YH becomes deglycosylated, resistant to detergent extraction, and zonular, and cells become epithelioid. Treatment with the N-glycosylation inhibitor tunicamycin induces an epithelioid phenotype in clone-YH, like time in culture but disrupts the hTERT-RPE1 phenotype. N-cadherin traffics to surface membranes and complexes with catenins regardless of cell type or glycosylation state, although catenin complex composition varied, showing enriched alpha-catenin under the cell-type-specific conditions in which N-cadherin was junctional. Clone-YH continued to express E-cadherin as a very minor cadherin, which trafficked to membranes but did not accumulate at junctions. CONCLUSIONS: RPE cells are not unique in localizing N-cadherin to a zonular adhesion typical of a monolayer epithelium, because even epithelial cells derived from a typically E-cadherin dominant line (clone-YH) form a zonular N-cadherin junction if the protein is abundant. However, there are cell and cadherin differences in mechanisms of cadherin accumulation in a zonular pattern, and a previously unrecognized cell-type-specific role for protein glycosylation in epithelial phenotype development.

Endogenous N-cadherin in a subpopulation of MDCK cells: distribution and catenin complex composition.

Epithelial (E)-cadherin plays a critical role in developing a normal epithelial phenotype but neural (N)-cadherin can disrupt epithelial shape, at least in carcinoma-derived cells. Here the normal epithelial cell line MDCK was used to select for a trypsin-sensitive (TS-MDCK) subpopulation that expresses low levels of endogenous N-cadherin. Similar amounts of E-cadherin and all catenins are found in both TS-MDCK and trypsin-resistant cells (TR-MDCK), but TS-MDCK are less phenotypically epithelioid and more motile, and junctional proteins are more detergent soluble. In TS-MDCK, N-cadherin is largely nonjunctional; a similar N-cadherin distribution and mesenchymal phenotype are found in TR-MDCK transfected to express low levels of exogenous N-cadherin. Little N-cadherin was attracted to junctions between TS-MDCK and hTERT-RPE1 cells, a retinal pigment epithelium-derived line that expresses dominantly N-cadherin. No differences were seen in E-cadherin-catenin complexes in TS- and TR-MDCK, but N-cadherin-catenin complexes in TS-MDCK have more abundant p120 catenin. Overall, the results indicate that E- and N-cadherin assemble stoichiometrically different complexes with p120 in the same cells. Further, N-cadherin does not participate with E-cadherin in a zonular epithelial junction in normal MDCK epithelial cells. Rather, even low levels of endogenous N-cadherin contribute to a disrupted epithelial phenotype, resembling the effect of N-cadherin on carcinoma-derived epithelial cells.