Thermoelectric Materials by Organic Intercalation

The smart wearable tech market is entering a new era, and Forbes has predicted that the market will be doubled by 2021. Flexible thermoelectric devices hold great promise for self-powering these wearable smart electronics. Although traditional inorganic-based thermoelectric generators are commercially available in the market, they are neither comfortable to wear nor efficient in capturing heat from non-flat surfaces. On the other hand, the development of flexible organic-based devices is still at the proof-of-the-concept stage, and the lack of high-performance and air-stable n-type organic semiconductors has become a bottleneck. In this chapter, we will present our recent progress in the development of n-type organic-intercalated flexible thermoelectric materials, paying particular attention to the transition metal dichalcogenide TiS2. We will discuss the material synthesis methods, their superlattice structures and functional roles of inorganic and organic layers. We will then focus on their unique transport properties and put forward some key strategies on how to tune their thermal conductivity, carrier concentration and mobility, which are essential for improving the overall thermoelectric performance. In addition, we will demonstrate a solution-processable approach to fabricating large-scale inorganic/organic superlattice films. The performance of a prototype flexible thermoelectric device will also be presented. Lastly, we will discuss the prospects and challenges in this field.