IEC 62607:2020, a Technical Specification, provides a method for determining the fluorescence lifetime of semiconductor quantum dots (QDs) using the time correlated single photon counting (TCSPC) technique. TCSPC is suitable for testing fluorescence lifetime in the range from picoseconds to nanoseconds. This document is only applicable to liquid samples that are stable dispersions of QDs. It is not applicable to solid samples. This document includes: – outlines of the experimental procedures, – data processing, and – case study.