Scientists have long regarded atomically-thin semiconductors as the future of electronics. Despite their infinitesimal thickness, such materials could pave the way for high-tech electronic devices, including transparent LED displays, miniature transistors and more efficient photovoltaic cells. However, currently available technologies are known to produce monolayer semiconductors that are riddled with flaws. As part of a recent project, a team of UC Berkeley scientists has come up with an innovative technique, by which these defects can be easily fixed.
For the research, published last month in the journal Science, the scientists chose to work with monolayer semiconductors made up of molybdenum disulfide (MoS2). Measuring only around seven-tenths of a nanometer in thickness, a layer of MoS2 is actually thinner than human DNA, which is about 2.5 nanometers in diameter. When treated with a special organic superacid, the material was found to exhibit an impressive 100-fold increase in its photo-luminescence quantum yield, which is basically a ratio of the amount of light produced by the substance to the quantity of energy provided. Speaking about the breakthrough, Ali Javey, a professor of electrical engineering and computer science at UC Berkeley, says:
Traditionally, the thinner the material, the more sensitive it is to defects. This study presents the first demonstration of an optoelectronically perfect monolayer, which previously had been unheard of in a material this thin.
According to the researchers, dipping the substance into a powerful superacid, known as bistriflimide (TFSI) actually led to the removal of contaminants from the material. Furthermore, a specialized chemical process called protonation helped fill the missing atoms, thus fixing the defects present in the MoS2 film. Monolayer semiconductors have several advantages, including their substantially low absorption of light as well as their ability to withstand severe mechanical deformation. These features make them the ideal choice for creating transparent and flexible electronic devices.
Potential applications include flexible LED displays that turn transparent when turned off and also, high-performing transistors that could in turn facilitate the miniaturization of modern electronics.
Source: UC Berkeley