Solution-Processed Semiconductors for Self-Powered Electronics Toward Sustainable Internet of Things

The dissemination of smart sensors as part of the Internet of Things (IoT) holds significant promise for advancing human development globally. However, the sheer size of the IoT device ecosystem poses key sustainability challenges.¹ On the one hand, the dissemination of IoT sensor nodes requires a sustainable approach to powering them—ideally, by harvesting ambient energy. On the other hand, to minimize the environmental impacts of the IoT device ecosystem, its sensor nodes should be fabricated using environmentally-friendly technologies.<br/>Emerging solution-processed semiconductors have considerable potential to address these sustainability challenges. Due to their low-temperature deposition in thin-film form, such semiconductors allow device fabrication with considerably lower energy and material consumption than conventional electronics. Additionally, the versatility of solution-processed semiconductors allows their use to fabricate electronic circuitry, sensors, and energy harvesters, potentially leading to the seamless, environmentally-friendly integration of IoT sensor nodes powered by ambient energy.<br/>To realize the potential of solution-processed semiconductors for sustainable IoT, we first established the paradigm of deep-subthreshold balanced ambipolarity, which enables ultralow-power printed thin-film-transistor (TFT) electronics.² By applying suitable self-assembled monolayers at the active interface of printed-carbon-nanotube TFTs, we obtained balanced ambipolar characteristics in the deep-subthreshold region. We could thus demonstrate deep-subthreshold ambipolar circuits capable of operating with a supply voltage down to 0.2 V and power dissipation down to the femtowatt range—the lowest to date for TFT electronics based on solution-processable semiconductors.²<br/>To assess the viability of self-powered electronics based on solution-processed semiconductors, we also investigated for the first time the application of lead-free perovskite-inspired materials (PIMs) to indoor photovoltaics (IPV) for ambient energy harvesting.^3,4 By tuning the structural dimensionality of solution-deposited cesium-antimony halides, we boosted their photoconversion efficiencies to state-of-the-art values.⁵ Specifically, two-dimensional Cs₃Sb₂Cl_xI_9-x delivered IPV efficiencies approaching 5%, i.e., already within the range of commercial IPV.³ Further, by combining our PIM IPVs with our ultralow-power TFT electronics, we could provide the first demonstration of printed TFT circuits operating in self-powered mode by harvesting ambient indoor light.<br/>Given the importance of photodetectors as sensing elements in IoT sensor nodes, we finally investigated the capability of emerging organic semiconductors and lead-free PIMs for self-powered light sensing. Specifically, by adopting a non-fullerene acceptor, we demonstrated self-powered narrowband organic photodetectors responsive in the far-red range with cutting-edge performance.⁶ Further, we studied the impact of structural dimensionality on the self-powered photodetection capabilities of antimony-based PIMs, achieving the highest performance to date for materials of this class.⁷<br/><b>References</b><br/>1 V. Pecunia, L. G. Occhipinti and R. L. Z. Hoye, <i>Adv. Energy Mater.</i>, 2021, 2100698.<br/>2 L. Portilla, J. Zhao, Y. Wang, L. Sun, F. Li, M. Robin, M. Wei, Z. Cui, L. G. Occhipinti, T. D. Anthopoulos and V. Pecunia, <i>ACS Nano</i>, 2020, <b>14</b>, 14036–14046.<br/>3 Y. Peng, T. N. Huq, J. Mei, L. Portilla, R. A. Jagt, L. G. Occhipinti, J. L. MacManus-Driscoll, R. L. Z. Hoye and V. Pecunia, <i>Adv. Energy Mater.</i>, 2021, <b>11</b>, 2002761.<br/>4 V. Pecunia, L. G. Occhipinti, A. Chakraborty, Y. Pan and Y. Peng, <i>APL Mater.</i>, 2020, <b>8</b>, 100901.<br/>5 Y. Peng, F. Li, Y. Wang, Y. Li, R. L. Z. Hoye, L. Feng, K. Xia and V. Pecunia, <i>Appl. Mater. Today</i>, 2020, <b>19</b>, 100637.<br/>6 K. Xia, Y. Li, Y. Wang, L. Portilla and V. Pecunia, <i>Adv. Opt. Mater.</i>, 2020, <b>8</b>, 1902056.<br/>7 J. Mei, M. Liu, P. Vivo and V. Pecunia, <i>Adv. Funct. Mater.</i>, 2021, 2106295.