Academic Research Papers from the projects funded in Phase 1 of the Network
NRN158 - Effect of Bias Current on Complexity and Time Delay Signature of Chaos in Semiconductor Laser with Time-Delayed Optical Feedback
IEEE Journal of Selected Topics in Quantum Electronics
The effect of bias current on the complexity and time-delay signature of chaotic signals in semiconductor lasers with polarization preserved optical feedback has been studied experimentally and theoretically. The peak value of the autocorrelation coefficient and the normalized permutation entropy at the feedback round trip time are used to quantify the time delay signature and complexity, respectively. The results show that the time-delay signature is approximately in an inverse relationship with the complexity of chaos when the semiconductor laser is subject to low or strong optical feedback. However, the inverse relationship disappears when the laser operates at higher bias currents with intermediate feedback strength. The simulation results are qualitatively agreed with the experimental results.
NRNC05 Virtual source aperture imaging and calibration for ultrasonic inspections through dual-layered media for non-destructive testing
Insight - Non-Destructive Testing and Condition Monitoring,
Since the introduction of full matrix capture to non-destructive testing (NDT), there have been advancements in software algorithms allowing for fully-focused imagery to be generated. Due to the large number of time-domain signals associated with this approach, processing speed is often a limiting factor. This paper describes an alternative, less processor-intensive approach in which a parallel transmission of a highly divergent beam is generated to simulate a virtual point positioned some distance behind the transducer.
NRN093 - Use of gas cluster ion source depth profiling to study the oxidation of OPV thin films by XPS
The analysis of organic materials such as phenyl-C61-butyric acid methyl ester (PC61BM) by depth profiling is typically fraught with difficulty due to the fragile nature of the sample. In this work we utilise a gas cluster ion source for the controlled depth profiling of organic materials that would historically have been too fragile to analyse and obtain quantitative compositional data through the whole thickness of the film. In particular we examine the oxygen diffusion and photo-oxidation kinetics of one of the most commonly used electron acceptor materials for many organic optoelectronic applications, namely PC61BM, in both neat films and in blends with polystyrene. Exposure to AM1.5G light and air under ambient conditions, results in a higher level of surface oxidation of blended PC61BM:polystyrene than is observed for either pure control film. Gas cluster ion source depth profiling further confirms that this oxidation is strongest at the extreme surface, but that over time elevated oxygen levels associated with oxidised organic species are observed to penetrate through the whole blended film. The results presented herein provide further insights on the environmental stability of fullerene based organic optoelectronic devices.
NRN094 - Application of luminescence downshifting materials for enhanced stability of CH3NH3Pbl3(1-x) Cl3x perovskite photovoltaic devices
The application of luminescent down shifting (LDS) layers as alternative UV filters for CH3NH3PbI3(1-x)Cl3x perovskite solar cell (PSC) devices is reported. A combination of photo-absorption measurements and of device decay measurements during light soaking are used to verify the stability. The application of a UV filter or LDS layer was able to significantly retard photo-induced degradation with ∼18% drop in device power conversion efficiency (PCE) observed over 30 h for non-encapsulated devices, which is compared to ∼97% for an un-filtered device, also without encapsulation. Whilst the PCE of the PSC device decreases with the application of the LDS layer, the drop is not as significant as when a commercial UV filter is used. Considering that UV filters will be essential for the commercialization of PSCs, the work provides evidence that the LDS layer can act as an alternative UV filter in PSCs and can limit the drop in PCE that can be expected from the inclusion of a UV filter, thus providing an added benefit over commercial UV filters.
NRN152 - A scaling law for monocrystalline PV/T modules with CCPC and comparison with triple junction PV cells
Scaling laws serve as a tool to convert the five parameters in a lumped one-diode electrical model of a photovoltaic (PV) cell/module/panel under indoor standard test conditions (STC) into the parameters under any outdoor conditions. By using the transformed parameters, a current-voltage curve can be established under any outdoor conditions to predict the PV cell/module/panel performance. A scaling law is developed for PV modules with and without crossed compound parabolic concentrator (CCPC) based on the experimental current-voltage curves of six flat monocrystalline PV modules collected from literature at variable irradiances and cell temperatures by using nonlinear least squares method. Experiments are performed to validate the model and method on a monocrystalline PV cell at various irradiances and cell temperatures.