GeTe-based alloys have been considered as p-type thermoelectric materials for decades. Yet the fact that they possess intrinsically high concentration of cation germanium vacancies have triggered the thermoelectric community in finding alternatives and strategies to optimize their efficiency. While most of the published studies mainly discuss the stoichiometric alloy, here we demonstrate the introduction of excess germanium/tellurium to the system. The nonstoichiometric alloy is doped with bismuth, acting as a donor simultaneously with an increased number of vacancies, enabling higher solubility of other impurities (iodine/indium). This strategy and the mechanisms involved, has been investigated and correlated to the microstructural characteristics. ZT of ~1.6 was obtained but more importantly, it opens the opportunity for a potential route for further thermoelectric enhancement.

几十年来，基于GeTe的合金被认为是p型热电材料。然而，它们本质上具有高浓度的阳离子锗空位，这一事实已经触发了热电界寻找优化其效率的替代方法和策略。尽管大多数已发表的研究主要讨论化学计量合金，但在这里我们证明了向系统引入过量的锗/碲。非化学计量合金掺有铋，同时作为施主同时增加了空位数量，从而使其他杂质（碘/铟）具有更高的溶解度。已经研究了该策略和涉及的机制，并将其与微观结构特征相关联。ZT 获得了约1.6的值，但更重要的是，它为进一步热电增强的潜在途径打开了机会。