A major challenge in thermoelectrics (TEs) is developing devices made of sustainable, abundant, and non-toxic materials. Furthermore, the technological drive toward low sizes makes crucial the study of nano and micro configurations. In this work, thin film TE devices based on p-type Cu 2+x Zn 1-x SnS 4 and Cu 2+x Zn 1-x SnSe 4 , and n-type Al y Zn 1-y O are fabricated by physical vapor deposition. The kesterite phases show good purity and promising TE power factor, likely enhanced by the copper-zinc order-disorder transition. Thin film generators in planar configuration are assembled by a sequential deposition of the p-type, n-type, and contact materials. The power per unit planar area reaches 153 and 279 nW cm -2 for the sulphurand selenium-based generators, respectively. These values significantly outperform any other literature attempt based on sustainable and low-cost thin films. Furthermore, if compared with traditional TEs often made of scarce and toxic materials, these devices offer a cost reduction above 80%. This allows reaching comparable values of power density per unit material cost, representing a first real step toward the development of sustainable and non-toxic thin film TE devices. These can find applications in micro energy harvesters, microelectronics coolers, and temperature controllers for wearables, medical appliances, and sensors for the internet of things.
The stability of organic semiconductors is an important topic, which in the case of organic thermoelectrics (OTEs), has not yet got the attention it deserves. This work presents a simple method which allows to characterize the stability of OTEs, using patterned ITO substrates to electrically contact encapsulated samples. The method is applied to n‐doped carbon nanotube films, a well‐suited reference system due to their sensitivity to changes in doping level, and used to compare the effectiveness of different encapsulation methods. In the observed films, oxygen adsorption leads to a gradual p‐doping. Among the investigated barrier materials, glass performs best. Flexible alternatives like transferred films of barrier polymers also show promise, while barrier films deposited by dropcast performed worse, likely due to their inhomogeneity. Finally, Raman imaging is shown to be a useful technique to investigate degradation in OTEs.
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