Planck constant is a fundamental concept in physical sciences, and Millikan received the Noble Prize for determining it experimentally in 1923. As the technology of solid state electronic devices developed, an experiment was designed and adapted to determine the Planck’s constant using LED [1, 2]. Herrmann and Schätzle [3] questioned the validity of this experiment on the basis of the diode equation, and their approach was further discussed by Morehouse [4]. In this article, the validity of this experiment is revisited.