Perhaps I missed this discussion in the article, but what are the theoretical advantages of these organic transistors over the traditional CMOS transistors motivating this research?
I don't know about the transistors in the article but generally organic transistors can be printed on flexible plastic substrates. The process doesn't need the same high temperatures and toxic chemicals that are needed for silicon transistors.
Being organic also means that they have a lower activation energy both for manufacturing AND FOR FAILURE. So they use less energy to make but that also guarantees they will fail sooner during use. Physics is a bitch!
BTW "GHz speeds" isn't much. Transistors from the 1950s achieved this - such a metric is the "Gain-Bandwidth product" which means "GHz" is the frequency at which the gain has fallen unity (the transistor has ceased to be useful in ANY way - a resistor has comparable "performance").
In the 1980s I worked with 50 GHz Gain-Bandwidth bipolar transistors. Most microwave transistors today are well into 100-200 GHz.
See https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5090443/