Electrochemically Deposited Polypyrrole for Dye-Sensitized Solar Cell Counter Electrodes

Polypyrrole films were coated on conductive glass by electrochemical deposition (alternative current or direct current process). They were then used as the dye-sensitized solar cell counter electrodes. Scanning electron microscopy revealed that polypyrrole forms a nanoparticle-like structure on the conductive glass. The amount of deposited polypyrrole (or film thickness) increased with the deposition duration, and the performance of polypyrrole based-dye-sensitized solar cells is dependant upon polymer thickness. The highest efficiency of alternative current and direct current polypyrrole based-dye-sensitized solar cells (DSSCs) is 4.72% and 4.02%, respectively. Electrochemical impedance spectroscopy suggests that the superior performance of alternative current polypyrrole solar cells is due to their lower charge-transfer resistance between counter electrode and electrolyte. The large charge-transfer resistance of direct current solar cells is attributed to the formation of unbounded polypyrrole chains minimizing the I3 − reduction rate

Analyzing the rotational motion of a rectangular board via smartphone sensors: a conservation-of-mechanical-energy approach

Abstract This paper describes the use of a smartphone’s motion sensors in investigating the rotational motion of a rectangular board rotating around a fixed axis. The smartphone’s motion, orientation, rotational rate, and acceleration are simultaneously recorded across the x-, y-, and z-axes. In the experiment, the experimental data (angular position and angular speed of the rotating board) were recorded and were processed to demonstrate the conservation of mechanical energy during rotation. We expect that this article gives an idea of how smartphone-based physics experiments can be useful for physics teachers. Moreover, this experiment helps students better understand the rotational motion of a rectangular board in relation to the conservation of energy.</jats:p

Influence of Acid Modification Multiwall Carbon Nanotube Counter Electrodes on the Glass and Flexible Dye-Sensitized Solar Cell Performance

Multiwall carbon nanotubes (MWCNTs) were modified by acids (H2SO4 : HNO3) for generating active groups on the nanotube surface. Unmodified- and modified-carbon nanotubes were coated on the conductive glass and conductive plastic substrates by a slurry paste method, and they were used as the counter electrodes (CEs) of dye-sensitized solar cells (DSSCs). Scanning electron microscopy reveals that carbon nanotubes are evenly deposited on the conductive glass. The efficiency of the glass based DSSCs of unmodified- and modified-carbon nanotubes and Pt CEs is ~4.73%, ~5.66%, and ~6.08%, respectively. The efficiency of the plastic based DSSCs of the unmodified- and modified-carbon nanotubes CEs is ~0.80% and ~2.11%, respectively. The voltammogram and electrochemical impedance spectroscopy results suggest that the superior performance of the modified-carbon nanotubes DSSCs is attributable to the high electrocatalytic activity and the low charge-transfer resistance of the modified-carbon nanotubes film over the unmodified-carbon nanotubes film

The Effects of CsBr Concentration on the Inorganic Cesium Lead Bromide Perovskite Film Properties and the Performances of Carbon-Based HTM-Free Perovskite Solar Cells

Inorganic cesium lead bromide (ICLB) perovskite films were prepared onto an FTO conductive substrate by a two-step spin-dipping method. PbBr2 films were first coated onto the FTO substrate, and then they were immersed into CsBr solutions at various concentrations: 0.04, 0.06, 0.08, 0.10, and 0.12 M, forming the ICLB perovskite films. The surface morphology of the perovskite films prepared from the CsBr concentrations under 0.08 M had a uniform crystalline surface, but the CsBr concentrations above 0.08 M gave the film a non-uniform structure. XRD spectra of all ICLB films compose of mixed phases of monoclinic-CsPbBr3 and tetragonal-CsPb2Br5. The direct optical bandgap of 2.3 eV corresponded to the CsPbBr3 phase, and the indirect optical bandgap of 2.87-3.10 eV corresponded to the CsPb2Br5 phase. Carbon-based hole-transport-material (HTM) free CsPb2Br5 - CsPbBr3 perovskite solar cells were assembled, and the CsPb2Br5 - CsPbBr3 perovskite solar cells prepared from 0.08 M CsBr concentration delivered the highest efficiency of 2.6%. This was because the 0.08 M-perovskite film had good uniformity, low pinhole defect, and low PbBr2 impurities. Good cell stability, with an efficiency reduction of 10.0% of the initial value after 816 h under ambient environment, was achieved from the 0.08 M CsBr concentration cells.</jats:p