I want to know the answer to the following question:
What substance did Barbieri use in his work with high-brightness LED?
All the background I'm provided with is that "In 1995, Alberto Barbieri at the Cardiff University Laboratory (GB) investigated the efficiency and reliability of high-brightness LEDs and demonstrated a "transparent contact" LED using indium tin oxide (ITO) on (AlGaInP/GaAs).". Is that enough to answer the question?