Surface Passivation of Nanoporous TiO2 via Atomic Layer Deposition of ZrO2 for Solid-State Dye-Sensitized Solar Cell Applications

We report here the utilization of atomic layer deposition to passivate surface trap states in mesoporous TiO2 nanoparticles for solid-state dye-sensitized solar cells based on 2,2′,7,7′-tetrakis(N,N-di-p-methoxyphenylamine)-9,9′-spirobifluorene (spiro-OMeTAD). By depositing ZrO2 films with angstrom-level precision, coating the mesoporous TiO2 produces over a two-fold enhancement in short-circuit current density, as compared to a control device. Impedance spectroscopy measurements provide evidence that the ZrO2 coating reduces recombination losses at the TiO2/spiro-OMeTAD interface and passivates localized surface states. Low-frequency negative capacitances, frequently observed in nanocomposite solar cells, have been associated with the surface-state mediated charge transfer from TiO2 to the spiro-OMeTA

Post-Assembly Atomic Layer Deposition of Ultrathin Metal-Oxide Coatings Enhances the Performance of an Organic Dye-Sensitized Solar Cell by Suppressing Dye Aggregation

Dye aggregation and concomitant reduction of dye excited-state lifetimes and electron-injection yields constitute a significant mechanism for diminution of light-to-electrical energy conversion efficiencies in many dye-sensitized solar cells (DSCs). For TiO₂-based DSCs prepared with an archetypal donor–acceptor organic dye, (<i>E</i>)-2-cyano-3-(5′-(5′′-(<i>p</i>-(diphenylamino)­phenyl)-thiophen-2′′-yl)­thiophen-2′-yl)­acrylic acid (<b>OrgD</b>), we find, in part via ultrafast spectroscopy measurements, that postdye-adsorption atomic layer deposition (ALD) of ultrathin layers of either TiO₂ or Al₂O₃ effectively reverses residual aggregation. Notably, the ALD treatment is significantly more effective than the widely used aggregation-inhibiting coadsorbent, chenodeoxycholic acid. Primarily because of reversal of <b>OrgD</b> aggregation, and resulting improved injection yields, ALD post-treatment engenders a 30+% increase in overall energy conversion efficiency. A secondary contributor to increased currents and efficiencies is an ALD-induced attenuation of the rate of interception of injected electrons, resulting in slightly more efficient charge collection

Novel 3-nitro-1H-1,2,4-triazole-based aliphatic and aromatic amines as anti-chagasic agents

A series of novel 2-nitro-1H-imidazole- and 3-nitro-1H-1,2,4-triazole-based aromatic and aliphatic amines were screened for anti-trypanosomal activity and mammalian cytotoxicity by the Drugs for Neglected Diseases initiative (DNDi). Out of 42 compounds tested, eighteen 3-nitro-1,2,4-triazoles and one 2-nitroimidazole displayed significant growth inhibitory properties against T. cruzi amastigotes (IC50 ranging from 40 nM to 1.97 microM) , without concomitant toxicity towards the host cells (L6 cells), having selectivity indices (SI) 44 to 1320. Most (16) of these active compounds were up to 33.8-fold more potent than the reference drug benznidazole, tested in parallel. Five novel 3-nitro-1,2,4-triazoles were active against bloodstream form (BSF) T. b. rhodesiense trypomastigotes (IC50 at nM levels and SI 220 to 993). An NADH-dependent nitroreductase (TbNTR) plays a role in the anti-parasitic activity, since BSF T. b. brucei trypomastigotes with elevated TbNTR levels were hypersensitive to tested compounds. Therefore, a novel class of affordable 3-nitro-1,2,4-triazole-based compounds with antitrypanosomal activity has been identifie