Rules for modelling in computer-aided fault tree synthesis

In the design of process plants safety has assumed an increasingly high profile. One of the techniques used in hazard identification is the fault tree, which involves first the synthesis of the tree and then its analysis. The construction of a fault tree, however, requires special skills and can be a time-consuming process. It is therefore attractive to develop computer aids for the synthesis stage to match those which already exist for the analysis of the tree. A computer based system for fault tree synthesis has been developed at Loughborough University. This thesis is part of a continuing programme of work associated with this facility. [Continues.

Ultrafast Spectral Dynamics of CsPb(Br_<i>x</i>Cl_1–<i>x</i>)₃ Mixed-Halide Nanocrystals

In this work we investigated the spectral dynamics of cesium lead mixed-halide, CsPb­(Br_<i>x</i>Cl_1–<i>x</i>)₃ perovskite nanocrystals probed with complementary spectral techniques: time-resolved photoluminescence and transient absorption spectroscopy. Mixed-halide perovskite nanocrystals were synthesized via a hot-injection method followed by anion exchange reactions. Our results show that increased Cl content in perovskite nanocrystals (<i>a</i>) diminished the photoluminescence quantum yield and gave rise to rapid radiative recombination of carriers; (<i>b</i>) resulted in rapid thermalization of hot carriers and low carrier temperatures, which suggests weaker hot-phonon bottleneck and Burstein–Moss effects; (<i>c</i>) decreased the bandgap renormalization energy, which suggests high exciton binding energy and poor charge extraction in Cl substituted perovskite nanocrystals; and (<i>d</i>) increased the number of carriers undergoing Auger losses, where Auger processes dominate over trap-assisted recombination. These findings provide a generalized framework to guide researchers as to when mixed-halide perovskite nanocrystals would be useful for optoelectronic technologies and when they would be detrimental to device performance