Correlated Roles of Temperature and Dimensionality for Multiple Exciton Generation and Electronic Structures in Quantum Dot Superlattices

Abstract

Quantum dot superlattices (QDSLs), which are one-, two-, and three-dimensional periodic superlattices composed of QDs, induce dimensionality dependent quantum resonance among component QDs and thus represent a new type of condensed matter exhibiting novel energy, exciton and carrier dynamics. We focused on the two important parameters, the dimensionality and temperature, identifying their correlated roles to determine the electronic and photoexcited properties intrinsic to each QDSL at each dimensionality and temperature. We computationally demonstrated that the multiple exciton generation is significantly accelerated at higher temperature especially in the higher-dimensional QDSLs, indicating their great advantage especially at ambient temperature compared to an isolated zero-dimensional QD. Both of the dimensionality and temperature can be crucial and correlated parameters for independent tailoring of the properties of the QDSLs without changing size, shape and compositions of component QDs. The physical insights and advantage of the QDSLs we found here will lead to designing efficient and space-saving optoelectronic and photovoltaic devices which work at ambient temperature.

Controlling the dimension of the quantum resonance in CdTe quantum dot superlattices fabricated via layer-by-layer assembly

“…Furthermore, the ability to combine different types of semiconductor QDs or combine semiconductor QDs with other nanoparticles will expand the possibilities of new material design including more complex heteronanostructures. QDSLs have been theoretically shown to have a higher multiple-exciton generation efficiency than isolated QDs 53 , and the efficiency changes depending on the dimension of QDSLs 54 . In this study, we were able to clarify the formation of the minibands based on the picture of the 1D, 2D, and 3D quantum resonance in the CdTe QDSLs.…”

Temperature‐Dependent Exciton Dynamics in CdTe Quantum Dot Superlattices Fabricated via Layer‐by‐Layer Assembly

“…Future studies on photophysical properties of QDSLs can be developed from the viewpoint of both fundamental and applied research by clarifying intra‐miniband relaxation dynamics in QDSLs through transient absorption measurements and by studying the multiple exciton generation [ 4 . 46 ] in QDSLs for the application to QD solar cells.…”

A Layered Photo-Anode Prepared Using TiO2 Nanocrystals with Different Sizes for Enhanced Light-Trapping in Quantum Dots-Sensitized Solar Cells

“…The peaks located at lower frequencies indicate that the QDSSCs have a larger τ e . The τ e can be calculated using Equation 1: 36 τ e = 1 2π f max [1] Q184 ECS Journal of Solid State Science and Technology, 8 (9) Q178-Q184 (2019)…”

“…ceived much attention because of their large absorption coefficient, tunable optical properties, and the possibility for multiple exciton generation and hot carrier extraction in QDs. [1][2][3][4] The configuration of the QDSSCs is analogous to that of the dye-sensitized solar cells, which includes a photo-anode based on QDs-sensitized mesoporous TiO 2 (m-TiO 2 ) nanocrystal (NC) films, polysulfide electrolyte (S n 2− /S 2− ) and a counter electrode (CE). The QDSSC has underwent a rapid increase in power conversion efficiency (PCE) in past several years.…”