A Bayesian approach to luminescent down-conversion.

Photon conversion embodies a range of promising possibilities in pushing the theoretical Shockley-Queisser efficiency model of classical solar cells. Luminescent down-conversion, despite its potential, is held back in practical applications due to the difficulty of proper characterization in no small part because of concurrent luminescent downshifting events. Recent advances have demonstrated the opportunity provided by photon correlation measurement for down-conversion characterization. In this methodological work, we present a general method based on Bayesian probabilities for deriving auto-correlation functions analytically. This method is then applied to the five down-conversion mechanisms reported in the literature and successfully tested against numerical simulations. We show that the zero delay auto-correlation function can be the most direct way to demonstrate down-conversion and assess its efficiency. Our analysis offers additional useful tools for the design of characterization experiments and emphasizes some universal behavior valid for all reported conversion mechanisms.