Superlattice formation of faceted PbS quantum dots with three-dimensionally aligned crystal orientation

Abstract

We report the successful fabrication of a superlattice film composed of PbS colloidal quantum dots (QDs) with a three-dimensionally coincident crystal orientation. Faceted QDs with a truncated octahedral shape were prepared and deposited in a solvent on a pyramidal microhole array prepared on a Si (100) substrate. During the deposition, facets of neighboring QDs came into contact with each other in the aligned microholes.The three-dimensional crystal orientation alignment was confirmed by X-ray pole figure mapping. Such QD superlattice film with aligned crystal orientation can contribute to the realization of high-energy conversion efficiency of semiconductor solar cells.

Exponential optical absorption edge in PbS quantum dot-ligand systems on single crystal rutile-TiO2 revealed by photoacoustic and absorbance spectroscopies

“…The purpose of this study is to focus on the impact the different crystal orientations of single crystal rutile-TiO 2 (R-TiO 2 ) substrates and the QD spacing have on the optical absorption of QD-ligands. We chose PbS QDs as these have been extensively studied and are candidate for high-efficiency and stability QDSCs [15,16,31,[34][35][36][37][38]. PbS QDs bear significant advantages due to the small effective masses of electrons (0.08 m 0 ) and holes (0.075 m 0 ) (m 0 : electron rest mass), high static dielectric constant (∼181), and large exciton Bohr radius (∼18 nm).…”

Theoretical study of multi-band solar cells with a single PbS quantum dot superlattice film as a light absorption layer

“…On the other hand, we have proposed the use of colloidal QDs to compose a single crystal-like QDSL based on the deposition method. [12][13][14][15][16] Colloidal QDs can be mass-produced in flasks at low cost with uniform shape. There is no essential problem in applying colloidal QDs to solar cells, and they have been studied for use as sensitizers or spin-coated films as light absorption layers.…”

“…[21][22][23][24] Based on the nature of selfassembling, we have successfully achieved a single crystallike QDSL layer with widespread periodicity using a template to limit the free motion of colloidal QDs during deposition in a solvent. 15) The template is an array of inverted pyramidal holes created by using anisotropic wet etching of Si single crystal substrate, and the directions of the holes are aligned at the atomic level. The template not only allows symmetric uniform colloidal QDs to be three-dimensionally close-packed, but also align the crystal orientations of packed QDs all in the same direction with the help of facets on the QD surface.…”

Long carrier lifetime in faceted PbS quantum dot superlattice fabricated by sedimentation method

“…We have proposed the use of colloidal QDs as a solution to the problems. [17][18][19][20][21][22][23][24] High uniform colloidal QDs can be manufactured relatively easily in large quantities with low cost. 25,26) When colloidal QDs are deposited in solution, they self-form superlattices about the size of the electron microscope field of view.…”

“…Using faceted PbS QDs, we have successfully fabricated the QD superlattice film in which the facets faced each other and the plane orientations of the adjacent QDs were aligned. 22,23) In this study, we investigated the optical emission lifetime of QD superlattice films. We investigated how the lifetime of energy states in QDs was affected by the deposition time and the presence of template used for film formation as a result of de-localization of carriers in intermediate bands.…”