Route Toward Sustainable Oxide TFTs: Does Thin Film Oxide Technology Offer a Pathway Toward More Sustainable Electronics?

Wearable, flexible, lightweight, and large-area electronics, able to adapt to arbitrary shapes, is a recent technology that promises to integrate sensing and data processing capabilities into everyday objects. This will allow connecting the digital and the physical worlds we live in and enable new innovative applications such as intuitive interfaces and smart textiles for continuous health and safety monitoring. Different technologies, including devices based on organic semiconductors and conventional silicon, are used to develop such wearable systems, however, devices made from novel oxide-based semiconductors currently have one of the best changes to result in electronic systems with sufficient electrical performance on flexible and large-area substrates. Yet, these exciting possibilities come at a price. If all the objects and surfaces around us are equipped with electronic sensor systems, these objects themselves transform into electronic devices, which in turn would massively increase the amount of electronic waste at the end of their lifetime. The same is true for plastic waste as currently most unobtrusive electronics are fabricated on polymer substrates. Furthermore, electronics that are operated near the human body must be safe and biocompatible. The perfect solution for these problems would be to fabricate electronics using environmentally friendly materials and processes, and to guarantee that the electronic components, after fulfilling their intended task, dissolve into their basic constituents, which are then entirely passive or safely absorbed into the nutrient cycle of our environment. Such transient and bioresorbable behavior has been demonstrated for several types of devices but is an underdeveloped approach in the field of oxide semiconductors. Here, motivations and challenges to combine the excellent electrical and mechanical properties of flexible oxide electronics with the environmental friendliness of bioresorbable electronics are explored. This is done by using the most important active building block of such electronics, namely, the TFT, as a model device (
Figure 1
). Besides assessing the various definitions of biocompatibility and environmental friendliness used in today’s research, the available classes of suitable materials and their impact in the electrical and environmental domain are described. Finally, an evaluation of how such materials can be integrated into working oxide transistors and which performance levels are achievable by these first examples of sustainable oxide TFTs is presented.