Hanyang University Researchers Achieve Controllable Doping in Organic Semiconductors

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Organic semiconductors are paving the way for a new generation of lightweight, flexible electronics, including bendable displays, printable circuits, wearable sensors, and devices that harvest energy from their surroundings. A key factor behind the performance of these technologies is doping—a process by which molecules are introduced into a semiconductor to control the number of charge carriers it can support.

Achieving the right amount of doping, however, remains a major challenge in organic semiconductors. Researchers have long sought doping systems that combine three important characteristics: strong doping ability, high controllability, and long-term stability. A recent and promising development called Lewis-paired dopants addresses two of these problems. These complexes, formed when two complementary molecules known as a Lewis acid and a Lewis base interact, are remarkably stable and offer exceptional doping strength. Unfortunately, their high reactivity makes it difficult to control the final doping level of the semiconductor material, which needs to be fine-tuned rather than simply maximized.

To tackle this problem, a research team led by Professor Jaeyoung Jang and Dr. Sang Beom Kim from Hanyang University, Korea, investigated whether the reactivity of Lewis-paired dopants could be controlled through smart solvent selection. Their study, was made available online in the Advanced Materials journal on March 29, 2026, demonstrates a practical strategy for achieving strong, controllable, and stable doping in organic semiconductors by regulating dopant behavior through solvent polarity.

The researchers focused on a Lewis-paired dopant composed of two molecules, DDQ and BCF, and examined how it behaved in six solvents with different polarities. Using spectroscopy techniques and advanced computational modeling, they discovered that in highly polar solvents, BCF gets captured by solvent molecules, preventing the dopant pair from forming efficiently when the solution is applied to the semiconductor. Conversely, in solvents with moderate polarity, such as ethyl acetate, this capture is short-lived. Simply put, as the mildly polar solvent evaporates during processing, BCF is gradually released and free to pair up with DDQ. This enables fine-tuned control over doping without damaging the semiconductor film nor altering the dopant chemistry itself.

Using ethyl acetate as the processing solvent, the team achieved finely tunable doping across multiple organic semiconductors, even ones considered chemically difficult to dope. The resulting materials reached a high thermoelectric power factor and Seebeck coefficient, which are key performance metrics describing how effectively a material converts heat into electrical energy. "Our simple solvent-mediated strategy provides a new way to optimize semiconductor doping without designing entirely new dopant molecules," says Prof. Jang. "This approach could pave the way to high-performance and stable organic thermoelectric materials for self-powered wearable devices and low-power sensors."

Because precise control of charge carriers is important in many organic electronic technologies, the findings of this work have broad engineering implications. Potential applications include thermoelectric generators, solar cells, organic light-emitting diodes, healthcare sensors, and Internet-of-Things devices. "We believe this concept will influence the design of future organic electronic materials and help accelerate the development of next-generation flexible and sustainable electronics," concludes Prof. Jang.