A aggregate of experiments and idea have helped researchers at King Abdullah university of technological know-how and technology (KAUST) to improve the knowledge of fundamental physics questions on molecular doping  -- these will underpin the improvement of organic sun cells and field impact transistors.
Molecular doping is an important technique of creating flexible and low-value optoelectronic devices such as natural sun cells and field impact transistors. The method involves the managed addition of impurities called dopants into conjugated polymer skinny films; this permits an otherwise electrically inert fabric to behave like a semiconductor.
but, dopants which are electron-donating (n-type) can easily become oxidized if not housed beneath vacuum or inert atmosphere. This reduces tool overall performance, that's a problem due to the fact many key processing steps are currently done under ambient conditions.
Max L. Tietze from the university's sun & Photovoltaics Engineering research middle (SPERC) and associates have now tested this instability hassle in greater element.
In 2013, the researchers validated that by way of the usage of natural semiconductors with sufficiently low power levels, they produced pretty strong n-type conductive movies. Getting this result by means of using a di-tungsten complex as their n-dopant became a wonder, due to the fact in pure movies a di-tungsten complicated straight away degrades in air. at the time, the researchers presented viable causes for this phenomenon: one is single electron switch from the dopant to the host material and the other is the formation of hybridized electronic states.
To advantage deeper insight into the underlying mechanism, the researchers exposed 4 forms of n-doped organic thin movies to air. however, they observed the passivation impact most effective in movies wherein the host material's electron affinity exceeds a important fee. any other strand of inquiry for the researchers changed into to use both conductivity measurements and photoemission spectroscopy to verify the findings.
The researchers have now teamed up with the principle organization led by Jean-Luc Bredas at KAUST. They confirmed that the formation of hybridized digital host-dopant states may be excluded by means of numerical calculations, an effect that is owed to the 3-dimensional (paddle wheel) shape of the di-tungsten complicated.
rather, it's miles conclusively shown that single electron transfer to oxygen-water complexes, which had been alleged to represent electron traps of an conventional intensity of three.6 eV in conjugated polymers, definitely governs the degradation of the n-doped films, and hence their passivation. for this reason, Tietze's crew ought to identify a preferred limit for accomplishing air solid molecular n-kind doping on a quantitative basis.
"This combination of experimental and high stage theoretical paintings honestly addresses the most recent questions regarding the fundamental physics of molecular doping," said Tietze.