New doping method puts up to 100× more mobile charges into organic semiconductors

Researchers have developed a new way to dope organic semiconductors that can produce up to 100 times more mobile electrical charges than conventional methods, potentially making these lightweight materials more useful for flexible electronics. The approach, called degradation-assisted doping (DAD), tackles a basic limitation in organic semiconductor doping. Chemical dopants transfer electrons to the semiconductor, but conventional dopants can eventually reach a limit on how many charges they can generate. The new method works differently. Instead of remaining active after transferring an electron, the chemical dopant breaks down, removing its reaction products from the process. This allows fresh dopant molecules to continue transferring electrons and increases the concentration of mobile charges in the semiconductor. Researchers from Concordia University, the Institut national de la recherche scientifique (INRS) and York University demonstrated the approach using P3HT, an organic semiconductor, and tris(pentafluorophenyl)borane, or BCF, as the chemical dopant. Dopants push past limits The team combined laboratory experiments with computer simulations to understand the chemical reactions behind the process. They used nuclear magnetic resonance, optical spectroscopy, electron paramagnetic resonance and calorimetry to track changes after BCF transferred an electron to P3HT. The experiments showed that BCF undergoes degradation after accepting an electron. This is important because the breakdown products no longer interfere with subsequent doping reactions. The process can therefore continue generating additional mobile charges rather than approaching the same limit as conventional chemical doping. The researchers also found that BCF produced higher conductivity in P3HT than other commonly used dopants. The result suggests that controlling the fate of the dopant after electron transfer could be as important as the initial charge-transfer step. Organic semiconductors are carbon-based materials that can conduct electricity. They are being studied for electronics that need to be thin, lightweight, flexible or potentially inexpensive. Unlike many conventional semiconductor materials, organic semiconductors can be processed into films and incorporated into flexible devices. However, their electrical performance depends heavily on doping. Increasing the number of mobile charge carriers can improve conductivity, but conventional chemical doping approaches can be constrained by chemical and thermodynamic limits. Higher charge, broader applications DAD provides a way to work around that limitation by making the dopant effectively self-removing after it has performed its charge-transfer role. The researchers say this creates a new strategy for designing organic semiconductor systems with higher levels of doping. The findings could be relevant to flexible electronics, optoelectronic devices and thermoelectric technologies, where better conductivity can improve device performance. The work may also help researchers develop new dopants designed specifically to degrade in controlled ways after transferring charge. The study does not establish a finished electronic device or demonstrate commercial-scale manufacturing. Instead, it identifies a chemical mechanism that could be used to improve organic semiconductor materials and gives researchers a route to explore higher doping levels. The research was jointly led by Melissa Berteau-Rainville of INRS and Ingo Salzmann of Concordia University, with researchers from York University and INRS also contributing to the work. The study was published in Nature Materials. Get the latest in engineering, tech, space & science - delivered daily to your inbox.With over a decade-long career in journalism, Neetika Walter has worked with The Economic Times, ANI, and Hindustan Times, covering politics, business, technology, and the clean energy sector. Passionate about contemporary culture, books, poetry, and storytelling, she brings depth and insight to her writing. When she isn’t chasing stories, she’s likely lost in a book or enjoying the company of her dogs.