The excitonic relaxation dynamics of perovskite adsorbed on mesoporous thin films of Al2O3 and NiO upon excitation at 450 nm were investigated with femtosecond optical gating of photoluminescence (PL) via up-conversion. The temporal profiles of emission observed in spectral region 670-810 nm were described satisfactorily with a composite consecutive kinetic model and three transient components representing one hot and two cold excitonic relaxations. All observed relaxation dynamics depend on the emission wavelength, showing a systematic time-amplitude correlation for all three components. When the NiO film was employed, we observed an extent of relaxation proceeding through the non-emissive surface state larger than through the direct electronic relaxation channel, which quenches the PL intensity more effectively than on the Al2O3 film. We conclude that perovskite is an effective hole carrier in a p-type electrode for NiO-based perovskite solar cells showing great performance.

Photoluminescence (PL) of a nanocrystalline film of methylammonium lead iodide perovskite (MAPbI3) sandwiched between an electrode of a fluorine-doped tin oxide (FTO) layer and an insulating film of poly­(methyl methacrylate) is found to increase and decrease significantly with the application of an external electric field ( F ext), depending on the direction of the applied field, based on the measurements of electrophotoluminescence (E-PL) spectra, i.e., field-induced change in PL spectra. The field-induced change in PL intensity is confirmed to originate from the field-induced change in the number of free carriers which induce radiative recombination, based on temporally resolved E-PL measurements. We propose that an internal field ( F int) exists even without application of F ext. The anisotropic behavior of the effect of F ext on PL is interpreted in terms of a synergy effect of F int and F ext; both fields are additive with the applied field direction from Ag to FTO electrode (positive direction) or subtractive with the opposite applied field direction (negative direction), where FTO is the positive electrode, resulting in an increased or decreased total electric field as well as quenching or enhancement of PL, respectively. The PL lifetime in the nanosecond region increased and decreased with an application of an electric field in the positive and negative directions, respectively, which is attributed to a field-induced change in the concentration of free carriers.

Word sense disambiguation (WSD) is one of the basic problems in natural language processing. Traditional WSD methods provide only one meaning for each word in a passage. However, we believe that textual information alone may not be sufficient to determine the exact meaning of each word which may better be resolved when higher-level knowledge becomes available. In this paper, we propose an alternative to WSD that we call "sense pruning". The objective now is to reduce the number of plausible meanings of a word as much as possible so as to reduce the amount of work in later processing. Sense pruning is guided by information derived from HowNet -a recently developed knowledge base.Two criteria were used for the evaluation: recall rate and complexity reduction (which is the reduction in the number of possible meanings of a sentence). Effect of the length of the analytical window was studied. For a corpus of 103 Chinese passages from Sinica, Taiwan, with an analytical window of nine words, we obtained a recall rate of 94.14% and reduced the number of possible sentence meanings by 65.3%.