Rao is one of the world's foremost solid state and materials chemists. He has contributed to the development of the field over five decades. His work on transition metal oxides has led to basic understanding of novel phenomena and the relationship between materials properties and the structural chemistry of these materials.
Rao was one of the earliest to synthesise two-dimensional oxide materials such as LaCuO. He was one of the first to synthesise 123 cuprates, the first liquid nitrogen-temperature superconductor in 1987. He was also the first to synthesis Y junction carbon nanotubes in the mid-1990s. His work has led to a systematic study of compositionally controlled metal-insulator transitions. Such studies have had a profound impact in application fields such as colossal magneto resistance and high temperature superconductivity. Oxide semiconductors have unusual promise.  He has made immense contributions to nanomaterials over the last two decades, besides his work on hybrid materials.
He shares co-authorship of more than 1750 research papers and has co-authored or edited more than 54 books.