Coherent Thermoelectric Power from Graphene Quantum Dots

Abstract

The quantum confinement of charge carriers has been a promising approach to enhance the efficiency of thermoelectric devices, by lowering the dimension of materials and raising the boundary phonon scattering rate. The role of quantum confinement in thermoelectric efficiency has been investigated by using macroscopic device-scale measurements based on diffusive electron transport with the thermal de Broglie wavelength of the electrons. Here, we report a new class of thermoelectric operation originating from quasi-bound state electrons in low-dimensional materials. Coherent thermoelectric power from confined charges was observed at room temperature in graphene quantum dots with diameters of several nanometers. The graphene quantum dots, electrostatically defined as circular n–p–n junctions to isolate charges in the p-type graphene quantum dots, enabled thermoelectric microscopy at the atomic scale, revealing weakly localized and coherent thermoelectric power generation. The conceptual thermoelectric operation provides new insights, selectively enhancing coherent thermoelectric power via resonant states of charge carriers in low-dimensional materials.

Electronic and optical properties of bulk and surface of CsPbBr3 inorganic halide perovskite a first principles DFT 1/2 approach

“…Recently, it has been reported a huge leap in the progress of PCE up to 23.3% from 3.8% in methylammonium lead iodide organic-inorganic hybrid perovskite compound (CH 3 NH 3 PbI 3 ) 3 , 4 . This unprecedentedly high value of PCE has been attributed to high bipolar charge carrier mobility ( 0.6 cm V s ) 5 , high absorption coefficient in visible light range, tunable bandgap, strong fluorescence quantum yield, balanced charge mobility (electron-hole), low rate of electron-hole pair recombination, high carrier lifetimes, and high diffusion lengths 6 – 10 . Also, the presence of an extraordinary optoelectronic properties in organic-inorganic hybrid lead-halide perovskite compounds have a wide application in photonics like light-emitting diodes, and lasers 8 , 11 – 14 .…”

Phonon anharmonicity: a pertinent review of recent progress and perspective

“…For thermoelectric materials, phonon anharmonicity is an important topic because it helps to reduce the thermal conductivity and thus enhances the ZT value. There are many strategies to reduce the thermal conductivity, such as "Phonon-glass Electron-crystal" [257], "Phonon-liquid Electron-crystal" [258], and lowering the dimensions [259]. Several classes of thermoelectric materials are currently under investigation, including complex chalcogenides [260,261], skutterudites [262], half-Heusler alloys [263], and metal oxides [264], etc.…”

Overview of Computational Simulations in Quantum Dots

“…Tremendous efforts have been put into the improvement of thermoelectric performances using QD structures . Haskins et al .…”

“…[99] Tremendous efforts have been put into the improvement of thermoelectric performances using QD structures. [100][101][102] Haskins et al [103] explored the thermoelectric potential of SiÀ Ge QDSL using GKM and MD simulations. It was reported that the dot sizes and spacing play dominant roles in the lattice Table 1.…”