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The effect of thickness on the p.p.m, level H2 gas sensitivity of SnO2 nanoparticle-based thick film resistors is reported. The nanoparticles are synthesized by a sol-gel method and the films are prepared using standard screen printing technology. The thickness of the films is varied from a few micrometers to a few hundred micrometers. The results indicate that the sample having thickness 76#m gives the maximum sensitivity. The mechanism of the change in sensitivity with thickness is discussed.

The performance of methylammonium lead triiodide (CH3NH3PbI3)‐based solar cells depends on the crystallization and controlled microstructure. Despite their high performance, long‐term stability is a paramount factor toward large area fabrication and potential industrialization. Herein, poly(vinylidene fluoride–trifluoro ethylene) (P(VDF‐TrFE)) is used as an additive into a low concentration–based perovskite precursor solution to control the crystallinity and microstructure. Perovskite layers of lower thicknesses are derived from low precursor concentration, however, they often suffer from severe voids and roughness. Introducing judicious quantities of P(VDF‐TrFE) improves the surface coverage and smoothness, as well as reduce the grain boundaries in the perovskite. An array of characterization techniques are used to probe the structural, microstructural, and spectroscopic properties. Impedance spectra suggest that the P(VDF‐TrFE) can improve the carrier lifetime and reduce the charge transfer resistance, which in turn allows improvment of photovoltaic performance. For an optimized concentration of P(VDF‐TrFE), the fabricated semitransparent solar cells yield a power conversion efficiency in excess of 10%, which supersedes pristine devices, along with improved stability. The device architecture and the fabrication technique provide an effective route to fabricate cost effective and visible‐light‐semitransparent perovskite solar cells.

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Lead sulfide nanoparticles were synthesized at room temperature via a simple chemical reaction. In this synthesis, 2-mercaptoethanol was used as the capping agent and sodium sulfide was used as a sulfur source. The products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), ultraviolet-visible (UVvis) spectroscopy and Fourier transform infrared (FT-IR) spectroscopy Electron microscopy study showed that without using a capping agent the bulk PbS is obtained, while adding the mercaptoethanol leads to production of nanoparticles. We found that the electronic absorption spectra as well as the particle sizes depend on the used capping agents. Two exitonic peaks with a large blue shift were observed when mercaptoethanol was used.

The thermal stability of C60 in pure oxygen has been investigated by in-situ FT-IR and thermogravimetric analysis (TGA). It is shown that at temperatures of about 250 °C, the C60 loses its spherically symmetric structure and is oxidized to an anhydride type species. The anhydride on exposure to air is converted to an acid which however reverts to the anhydride on heating in a nitrogen or oxygen atmosphere. On heating beyond 250 °C, the C60 is completely oxidized probably to CO and CO2, but this complete oxidation appears to take place in two stages with the anhydride part of the molecule getting oxidized first. It is postulated that the lower oxidative stability of C60 compared to graphite is probably due to the greater reactivity towards oxygen of the pentagon–hexagon junction, compared to the hexagon–hexagon junction, present in C60.

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