Maarit Karppinen1

1, Aalto Univ, Espoo, , Finland

Development of high-performance power sources that comply with the continuously decreasing microscale dimensions of electronic devices is one of the major challenges in the IoT era. To address this challenge, we are working on new inorganic-organic thin-film materials for next-generation flexible energy harvesting and storage technologies. An elegant, yet industrially feasible way to fabricate such materials is to combine the ALD (Atomic Layer Deposition) technique originally developed to deposit high-quality thin films of simple inorganic materials with MLD (Molecular Layer Deposition) cycles based on organic precursors. This enables the atomic/molecular layer-by-layer production of inorganic-organic hybrid thin films through sequential self-limiting gas-surface reactions with high precision for the film thickness and composition.

Our hybrid inorganic-organic materials consisting of well-defined nanoscale layers of both components are promising candidates for enhanced thermoelectric materials, as such a layered structure provides us with the means to suppress the material’s thermal conductivity as a whole without significantly hindering the electrical transport properties of the individual inorganic layers. Moreover, the ALD/MLD fabrication technique employed allows the deposition of these materials directly on complex/flexible surfaces thus enabling the integration with e.g. textiles.

Another exciting application possibility for our hybrid thin films is in the all-solid-state organic thin-film microbattery. Organic electrode materials contain light, abundant and environmentally benign elements only, and show very high specific capacities, but in bulk form their poor electronic conductivity hinders the rate performance significantly. In a thin-film form this obstacle can be superbly circumvented. For our all-ALD/MLD fabricated microbattery with ultrathin Li-benzoquinone electrode and LiPON electrolyte layers, ultrahigh redox reaction rates are realized, such that it actually is able to combine the high energy density of batteries with the high power density of supercapacitors.