Looking at phosphorescence with a smartphone, explaining phosphorescence with a dice toy model

We present an educational approach to the phenomenon of phosphorescent emission. The approach is based on a stochastic toy model, in which electron states are represented by rows of squares on a cardboard table, and coins on the squares switch from one row to the other based on the roll of two dice. The discussion of different mechanisms, giving an exponential law decay or a power law decay, proceeds through a comparison between the outcomes obtained with the toy model and the results of a real experiment which students can make in a didactic laboratory by themselves using simple and inexpensive apparatus based on the use of a smartphone. The educational proposal, founded on a microscopic basis, goes on by considering the problem in statistical and probabilistic terms, and allows students to compare experimental data they obtain to both analytical results and simulations. The experiment and the model, with the aim of explaining phosphorescence in semiconductor materials, introduce students to some basic concepts of solid state physics such as valence and conduction bands, holes, excitations and recombination of electrons and holes.