Sean William Calhoun | Composer and pianist

When Laura Lentz and I were planning the piece, she was looking for it to pertain to climate change, and I thought a good focus would be on what people are doing to ameliorate it, so I started looking into recent developments in energy technology. Thus I learned how a team at the University of Rochester led by Chunlei Guo recently made developments dramatically improving the efficiency of perovskite solar cells. Perovskites are a type of crystal structure which can be formed by different combinations of elements, and solar cells made with them are potentially a much less expensive alternative to the current silicon solar cells. However, perovskite cells have faced issues of being less efficient and less durable than silicon. The developments at University of Rochester can solve one of those major hurdles to the practicality of perovskite solar cells.

The first movement, Light on Perovskite features many quick descending figures representing the beams of sunlight striking the perovskite. These increase in intensity, leading directly into the second movement Excitons. When a photon hits a crystal, it can knock an electron into a higher energy state, leaving a hole at its former energy state, which, despite being the absence of a particle, kind of acts like a positively-charged particle. The electron-hole pair is called an exciton. The electronics for the movement alternate between electron music — bright, distorted, and bassy — and hole music — light plucks and pulsing reverb tails. Being oppositely-charged, the electron and hole are attracted, and so the length of each pair of sections becomes progressively shorter until each is less than a beat. But for a solar cell to work, we need to use the charges to generate power, and that doesn’t happen if the exciton recombines on its own, so a part of solar cell efficiency is reducing the rate of recombination of excitons. And that’s where the titular plasmonic mirror comes in — the UofR team found that a thin layer of certain substances beneath the layer of perovskite could create a sort of mirror that, through Weird Physics Reasons (that I never really managed to understand), suppresses the recombination of excitons. So The Mirror of Recombination Reduction has a drone in the electronics representing the mirror, and for everything the flute plays, a part in the electronics plays an inversion of it slightly later below the mirror. Photoresponsivity is the term for the amount of electrical output relative to optical input, so the movement Photoresponsivity is a high-energy celebration of the greater efficiency of the perovskite solar cells.