Thin-film transistors (TFTs) based on transparent oxide semiconductors, which are colorless and transparent in the visible light region, are widely used as backplane devices for driving organic light-emitting diode (OLED) pixels at high switching speeds in OLED displays found in flat-panel televisions, smartphones, and tablets. Among these, the InGaZnO4 TFT developed by Nomura, Ohta, Hosono, and co-workers in 2004 (Nature, 2004) has become the dominant technology. However, the development of TFTs with even higher electron mobility, as well as p-type TFTs in which holes serve as the charge carriers, is expected to enable next-generation displays with higher resolution and faster response speeds. In our research field, we elucidate charge transport properties using our original thermopower field-modulation method and contribute to the development of high-performance TFTs.

While a TFT is a device that modulates electrical current through the application of a gate voltage, a thermal transistor is a device that controls the flow of heat (heat flux) in response to external electrical, magnetic, or thermal stimuli. Heat is generated in a wide range of systems, including electronic devices, batteries, power electronics, and engines. Traditionally, thermal management has focused on how efficiently generated heat can be removed from a system, making heat dissipation the primary challenge. However, as modern electronic and energy devices continue to become more powerful and highly integrated, simply dissipating heat is no longer sufficient. Advanced thermal management strategies are increasingly required, in which heat flow can be controlled both temporally and spatially. For example, heat may need to be retained when advantageous and released rapidly at other times. Meeting these demands requires not only conventional thermal conductors and heat sinks with fixed properties, but also new technologies capable of actively controlling heat flow itself. Thermal transistors represent a promising approach to achieving such dynamic control of heat transport.

Solar cell technologies have advanced significantly over the past decade, with perovskite solar cells emerging as one of the most promising for next generation photovoltaics. These advances have also stimulated growing interest in exploring alternative photoabsorber materials that can expand the range of materials available for efficient and sustainable solar energy conversion. In this context, pioneering work by Cojocaru et al. on demonstrated the potential of metal chalcogenide AgBiS2  thin films as photovoltaic absorber through a simple solution-based crystallization approach. Motivated by these developments, our research uses AgBiS2 and related modified structures as model systems to investigate the fundamental relationships between chemical composition, crystal structure, thin film morphology and optoelectronic properties. By deepening the understanding of the physical mechanisms underlying the behavior of photoabsorber materials and their impact on photovoltaic performance we aim to develop new semiconductor materials prepared by solution-process thin films for efficient and sustainable solar cells and other optoelectronic applications.