Photovoltaic conversion has made impressive progress since its discovery, but as will be discussed here, much can still done. It is of interest to investigate what are the intrinsic limits technology. We call here ultimate performance those that could limited only by properties devices. This point along three lines: for energy conversion, material usage and device stability.

This paper studies the population of chess players and the distribution of their performances measured by Elo ratings and by computer analysis of moves. Evidence that ratings have remained stable since the inception of the Elo system in the 1970’s is given in several forms: by showing that the population of strong players fits a simple logistic-curve model without inflation, by plotting players...