Flexible thermoelectric modules based on ALD-grown ZnO on different substrates

The authors have designed and tested prototype thin-film thermoelectric devices based on 100-500 nm thick layers of n-type ZnO fabricated with atomic layer deposition on different substrate materials: oxidized silicon, polyethylene naphtalate plastics, and thin flexible glass. In addition, they address the benefits of depositing intermittent organic (benzene) layers within the ZnO matrix through molecular layer deposition for thermal conductivity suppression. Thermoelectric performance of the test devices composed of several ZnO or ZnO:benzene thin-film legs was evaluated by generating the temperature difference using a hotplate and measuring the output voltage at the ends of the circuit in both open circuit and load configurations. The output voltage was found to increase with increasing ZnO film thickness. Most interestingly, the ZnO:benzene superlattice film investigated had better performance compared to plain ZnO of the same thickness, thus opening the way to further developments of thermoelectric thin-film devices.