In the current era where many renewable energy technologies are commercially mature and optimized, thermoelectrics remain relatively under-utilized. This can be partly attributed to their limited device efficiencies despite their high materials performances. On the materials level, the performance of thermoelectrics can be defined by zT or average zT, which is directly correlated to device power conversion efficiency. Due to this direct correlation, it is a longstanding assumption that maximizing average zT will result in higher efficiency. Although this practice holds true for many cases, it does not provide a complete picture due to the complex interplay between electronic and thermal transport properties. In this work, we surveyed the literature to find that high average zT does not always translate to high efficiency. Instead, it was found that compatibility factor, which dictates the optimal ratio of electrical and heat current passing through the material, is equally important in determining the device efficiency. Other factors such as electrical and thermal impedance matching, as well as contact resistance are also discussed. This review concludes with food for thought on future thermoelectric research beyond average zT to realize the untapped potential in this special class of materials.

在许多可再生能源技术在商业上成熟和优化的当今时代，热电技术仍未得到充分利用。这可以部分归因于尽管它们具有很高的材料性能，但它们的设备效率有限。在材料层面，热电材料的性能可以用zT或平均zT来定义，它与器件功率转换效率直接相关。由于这种直接相关性，长期以来一直假设最大化平均zT会带来更高的效率。尽管这种做法适用于许多情况，但由于电子和热传输特性之间复杂的相互作用，它并不能提供完整的情况。在这项工作中，我们调查了文献，发现高平均zT并不总是转化为高效率。相反，人们发现相容性因素决定了通过材料的电流和热流的最佳比例，在确定设备效率方面同样重要。还讨论了其他因素，例如电阻抗和热阻抗匹配以及接触电阻。这篇综述以超越平均zT 的未来热电研究值得深思的结尾实现这种特殊材料的未开发潜力。