From Hardassetsinvestor.com: Although it had already been used to coat mirrors (equal in quality to those made with a coating of silver), indium really only came into its element during World War II, when it was used to coat bearings in fighter aircraft.
But in the last 20-30 years, commercial use of indium has taken off, particularly with the development of flat-panel displays, semiconductors and photovoltaic cells………………………………….Full Article: Source