Reducing Domain Density Enhances Conversion Efficiency in GeTe

• Published in: Small (Weinheim an der Bergstrasse, Germany) Germany), 2024-08, Vol.20 (31), p.e2312206-n/a
• Main Authors: Tsai, Yi‐Fen, Yang, Min‐Jung, Deng, Jie‐Ru, Liao, Chien‐Neng, Wu, Hsin‐Jay
• Format: Article
• Language: English
• Subjects: conversion efficiency; defect density; Defects; Density; dilute doping; figure‐of‐merit; GeTe; Precipitates; Pressing; strain; Temperature gradients; Transport properties
• ISSN: 1613-6810; 1613-6829; 1613-6829
• DOI: 10.1002/smll.202312206

Incorporating dilute doping and controlled synthesis provides a means to modulate the microstructure, defect density, and transport properties. Transmission electron microscopy (TEM) and geometric phase analysis (GPA) have revealed that hot‐pressing can increase defect density, which redistributes strain and helps prevent unwanted Ge precipitates formation. An alloy of GeTe with a minute amount of indium added has shown remarkable TE properties compared to its undoped counterpart. Specifically, it achieves a maximum figure‐of‐merit zT of 1.3 at 683 K and an exceptional TE conversion efficiency of 2.83% at a hot‐side temperature of 723 K. Significant zT and conversion efficiency improvements are mainly due to domain density engineering facilitated by an effective hot‐pressing technique applied to lightly doped GeTe. The In–GeTe alloy exhibits superior TE properties and demonstrates notable stability under significant thermal gradients, highlighting its promise for use in mid‐temperature TE energy generation systems. Domain density modification coupled with the incorporation of trace indium in GeTe significantly elevates the peak figure‐of‐merit (zT) to 1.3 and achieves a 3% thermoelectric conversion efficiency at 700 K. These enhancements stem from strain redistribution via hot‐pressing and carrier concentration optimization through the reduction of germanium vacancies, bypassing the need for additional doping.