A comparative analysis on five edible oils with the same chemical composition but different composition ratios was performed by using coherent anti‐Stokes Raman scattering spectroscopy in the wavenumber 2400–3200 cm−1 corresponding to C─H vibration band. Intensity ratio (I═C ─ H/IC ─ H) in C─H stretching region was obtained according to the mixing ratio of the two types of edible oil, and the fitting curves were obtained from the fact that the intensity ratio is proportional to the square of N═normalC─normalHtrue/NnormalC─normalH where Nk is the expectation value of k bonds of the edible oil. N═normalC─normalH and NnormalC─normalH of the edible oils obtained from the fitting curves were well matched with the referred values. And finally, we showed that the coherent anti‐Stokes Raman scattering spectroscopy can be used as a method of authentication of adulterated edible oil by demonstrating a method to determine the type and the amount of unknown mixed oil.

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Understanding the excited-state dynamics in perovskite photovoltaics is necessary for progress in these materials, but changes in dynamics depending on the fabrication processes used for perovskite photoactive layers remain poorly characterised. Here we report a comparative study on femtosecond transient absorption (TA) in CH3NH3PbI3 perovskite films fabricated by various solution-processing methods. The grain sizes and the number of voids between grains on each film varied according to the film synthesis method. At the low excitation fluence of 0.37 μJ cm−2, fast signal drops in TA dyanmics within 1.5 ps were observed in all perovskite films, but the signal drop magnitudes differed becuase of the variations in charge migration to trap states and band gap renormalisation. For high excitation fluences, the buil-up time of the TA signal was increased by the activated hot-phonon bottleneck, while the signal decay rate was accelerated by fluence-dependent high-order charge recombination. These fluence-dependent dynamics changed for different perovskite fabrication methords, indicating that the dynamics were affected by morphological features such as grain sizes and defects.

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