He received his Ph.D. in Physics from the National University of Singapore (NUS) in 2005. His present research focuses on investigating light–matter interactions and energy and charge transfer mechanisms and probing carrier and quasi-particle dynamics in a broad range of emergent nanoscale and light harvesting systems. Prof. Sum has published 158 papers in peer reviewed journals. His publications have received ~5044 (Scopus) citations and his H-index is 34 (Scopus).