Laser Emission from Self-Assembled Colloidal Crystals of Conjugated Polymer Particles in a Metal-Halide Perovskite Matrix

Here, we present a hybrid organic/inorganic photonic composite, which generates laser emission from the organic material after pumping the inorganic component. The composite consists of a methylammonium lead-halide perovskite matrix CH3NH3Pb(BrxCl(1-x))3 and monodisperse poly(fluorene-co-divinylbenzene) particles, which have excellent optical feedback and gain. Micrometer-sized conjugated polymer particles (CPPs) are deposited together with the perovskite precursor from solution using a single-step vertical deposition method. The particles self-assemble into a photonic crystal and the perovskite forms an inorganic matrix in the interstitial space. Energy transfer to the polymer particles after optically pumping the metal-halide perovskite is studied in two systems with different halide ratios in the perovskite (Br to Cl: 1/9 and 4/6) to control the overlap of the perovskite emission energy with the absorption of the particles. From time-resolved photoluminescence experiments, we observe nonradiative energy transfer from the perovskite to the particle in both coassemblies; however, increased spectral overlap of perovskite emission and particle absorption enhances energy transfer efficiency by 37%. Because of the ordered assembly of the CPPs, we observe laser emission after energy transfer from the Cl-rich perovskite matrix at fluences of 13 mJ/cm2. Our report of a hybrid material system that combines the excellent opto-electronic properties of metal-halide perovskites with the outstanding optical properties of conjugated polymers represents a new approach and progress in the pursuit of electrically pumped polymer lasers

Degrees of truth, Ill-Known sets and contradiction

Outcome of the 2008 Conference on Information Processing and Management of Uncertainty (IPMU) in Málaga, SpainInternational audienceIn many works dealing with knowledge representation, there is a temptation to extend the truth-set underlying a given logic with values expressing ignorance and contradiction. This is the case with partial logic and Belnap bilattice logic with respect to classical logic. This is also true in three-valued logics of rough sets. It is found again in interval-valued, and type two extensions of fuzzy sets. This paper shows that ignorance and contradiction cannot be viewed as additional truth-values nor processed in a truth-functional manner, and that doing it leads to weak or debatable uncertainty handling approaches