Nanocrystalline CsPbCl/sub 3/: grain boundary transport properties

Abstract

Recently the ternary compound CsPbCl/sub 3/ produced by co-evaporating CsCl and PbCl/sub 2/ has attracted much interest for its interesting optical characteristics. Indeed, aggregates with dimensions of about 10 nm are produced in the material as evidenced by luminescence spectroscopy and X-ray diffraction. Identification of the aggregates is based on a similarity of the observed emission properties with those of the bulk material. CsPbCl/sub 3/ is a wide-gap semiconductor with direct band-to-band transitions. The phase diagram of the CsCl-PbCl/sub 2/ system reveals the existence of complex ternary CsPbCl/sub 3/ (phase III semiconductor) and Cs/sub 4/PbCl/sub 6/ (phase VI, insulator) compounds. Varying the deposition rate the phase III is deposited together with the insulating phase VI. The crucible temperatures have also been optimized to control the deposition rate in order to achieve the ternary phase III only. The aim of this paper is to report on the preparation, optical and electrical characteristics of bulk and vacuum evaporated ternary compounds. To our knowledge this is the first time that the electrical behaviour in dark and in light is reported for these compounds. The correlation of the aggregate dimensions with the exciton absorption will be also introduced and discussed. X-ray diffraction spectroscopy is used as an independent evidence for aggregated phase creation. Samples used for this study have been grown by vacuum evaporation starting from Bridgman crystal chips of CsPbCl/sub 3/ or by co-evaporation of CsCl and PbCl/sub 2/ purified powders onto 7059 Coming glass substrates.