USHAKOVA Elena St.Petersburg National Research University of Information Technologies, Mechanics and Optics

Self-Assembly of PbS Quantum Dots in Ordered Superstructures

Co-authors GOLUBKOV Valery, LITVIN Alexandr, PARFENOV Peter, CHEREVKOV Sergei, FEDOROV Anatoly, BARANOV Alexander

NIR-emitting colloidal quantum dots (QDs) attract much attention due to their unique properties in order to utilize in diverse areas of applications: from bio-sensing to solar cells fabrication. The self-assembly of QDs in a periodically ordered superstructures, such as superlattices and supercrystals, enables a formation of a new class of functional materials with remarkable optical, electronic, and vibrational properties. The deep understanding of driving mechanisms of this process is crucial for the engineering of devices based on QDs, such as LEDs, solar cells, photodetectors, and thermoelectric converters. In this study we investigated the structures, obtained by self-assembly of lead sulfide (PbS) QDs of different sizes deposited on a mica substrate. The test samples were prepared by a method based on the evaporation of a saturated solution. To investigate the nano- and micrometer scale inhomogeneities, including size of the quantum dots, as well as their relative positions on the substrate, methods of X-ray structural analysis were used. The obtained data suggested that the nanostructures obtained by QDs self-assembly represent ordered structures with diffraction patterns similar to that obtained for conventional crystals. The positions of the scattering peaks at SAXS patterns were used for calculation of the crystal structure of the samples. It was shown that these structures have a primitive orthorhombic lattice with size of tens of micrometers. This work is of considerable interest for the development of solar cells based on QDs superstructures, absorbing light in NIR-region.