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Photoexcited metals can produce highly-energetic hot carriers whose controlled generation and extraction is a promising avenue for technological applications. While hot carrier dynamics in Au-group metals have been widely investigated, a microscopic description of the dynamics of photoexcited carriers in the mid-infrared and near-infrared Pt-group metals range is still scarce. Since these materials are widely used in catalysis and, more recently, in plasmonic catalysis, their microscopic carrier dynamics characterization is crucial. We employ \emph{ab initio} many-body perturbation theory to investigate the hot carrier generation, relaxation times, and mean free path in bulk Pd and Pt. We show that the direct optical transitions of photoexcited carriers in this metals are mainly generated in the near-infrared range. We also find that the electron-phonon mass enhancement parameter for Pt is 16 $\%$ higher than Pd, a result that help explains several experimental results showing diverse trends. Moreover, we predict that Pd (Pt) hot electrons possess total relaxation times of up to 35 fs (24 fs), taking place at approximately 0.5 eV (1.0 eV) above the Fermi energy. Finally, an efficient hot electron generation and extraction can be achieved in nanofilms of Pd (110) and Pd (100) when subject to excitation energies ranging from 0.4 to 1.6 eV., Comment: Accepted for publication in Physical Review B

Metal halide perovskite (MHP) optoelectronics may become a viable alternative to standard Si-based technologies, but the current lack of long-term stability precludes their commercial adoption. Exposure to standard operational stressors (light, temperature, bias, oxygen, and water) often instigate optical and electronic dynamics, calling for a systematic investigation into MHP photophysical processes and the development of quantitative models for their prediction. We resolve the moisture-driven light emission dynamics for both methylammonium lead tribromide and triiodide thin films as a function of relative humidity (rH). With the humidity and photoluminescence time series, we train recurrent neural networks and establish their ability to quantitatively predict the path of future light emission with <11% error over 12 hours. Together, our in situ rH-PL measurements and machine learning forecasting models provide a framework for the rational design of future stable perovskite devices and, thus, a faster transition towards commercial applications.

The plasmon resonance of a structure is primarily dictated by its optical properties and geometry, which can be modified to enable hot-carrier photodetectors with superior performance. Recently, metal-alloys have played a prominent role in tuning the resonance of plasmonic structures through chemical composition engineering. However, it has been unclear how alloying modifies the time dynamics of generated hot-carriers. In this work, we elucidate the role of chemical composition on the relaxation time of hot-carriers for the archetypal Aux Ag1-x thin-film system. Through time-resolved optical spectroscopy measurements in the visible wavelength range, we measure composition-dependent relaxation times that vary up to 8x for constant pump fluency. Surprisingly, we find that the addition of 2% of Ag into Au films can increase the hot carrier lifetime by approximately 35% under fixed fluence, as a result of a decrease in optical loss. Further, the relaxation time is found to be inversely proportional to the imaginary part of the permittivity. Our results indicate that alloying is a promising approach to effectively control hot-carrier relaxation time in metals.