The rapid rise of power conversion efficiency of metal-halide perovskite solar cells beyond 20 % has drawn huge attention. Recent certified efficiencies, however, have been marked as “unstabilized” as perovskite solar cells tend to show a hysteretic behaviour during current density-voltage (J-V) measurements. This leads to deviating results for varying scan parameters and conditions, which challenges reliable and comparable results. In particular, the extent of this behaviour is highly dependent on device preparation method, architecture, device history, and more importantly on measurement preconditions and scan rate. Thus, the demand for reliable stabilized values arises which are reproducible and comparable among different laboratories. Here we introduce an adaptive tracking of the maximum power point and the open circuit voltage. We compare these values with device characteristics derived from standard J-V measurements. Furthermore, we discuss the challenges of a correct efficiency determination and provide the algorithms for easy implementation in existing measurement systems.
ZnO as a wide band gap semiconductor is of significant interest for various applications, including dye-sensitized solar cell (DSSC) and photocatalytic degradation of organic pollutants. For DSSC, although the performance of ZnO-based devices is generally inferior to TiO2-based ones, it is still of interest due to its high electron mobility. While the relationship between the material and the device performance are complicated, many studies have been focused on morphologies and surface area of the nanomaterials. The studies of the effect of the material properties such as the types and concentrations of native defects on the DSSC performance have been scarce. For photocatalytic degradation of pollutants, many reports showed ZnO has a higher or similar efficiency compared to the commonly used TiO2. Reports have also pointed out the important role of native defects of ZnO in its photocatalytic activity. Nevertheless, the effect of the type and location of the defects has been contradictory in the literature indicating that there is a complex relationship. Therefore, we will discuss the effect of ZnO native defects on the dye adsorption, charge transport and hence the DSSC performance. We will also discuss their influence on reactive oxygen species (ROS) generation and photocatalytic dye degradation. As photoluminescence (PL) is a common methodology in studying native defects of ZnO, the relationship between PL, DSSC performance and photocatalytic properties will also be investigated. Preliminary results showed a higher overall PL intensity would result in a better device performance and higher photocatalytic activities.
Nanostructures of the tin oxide, indium oxide and tin-doped indium oxide have been fabricated on silicon by chemical
vapor deposition from a mixture of metal oxide nanoparticles and single-wall carbon nanotubes (SWCNT). Different
ratios of the metal oxide to SWCNT have been used. It was found that the morphology of the nanostructures depends on
the substrate temperature. The morphology, growth direction and optical properties have been studied by scanning
electron microscopy, transmission electron microscopy and photoluminescence spectroscopy.
We investigated the influence of the growth method, growth conditions, and post-growth treatments on the ZnO nanorod
properties and the performance of heterojunction light emitting diodes (LEDs) based on ZnO nanorods. Due to small
lattice mismatch between GaN and ZnO, we will mainly consider p-GaN/n-ZnO nanorod heterojunctions. The influence
of p-GaN substrate and the influence of growth method and growth conditions used for ZnO nanorods on the LED
performance will be discussed.
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