ThermodynamicsShockley-Queisser is a limit on single-junction cells.
The SQ bound is a rigorous thermodynamic result for a single junction illuminated by a blackbody spectrum under detailed balance — it is not a bound on solar conversion in general. Relax the single-junction assumption and the bound lifts. The polyhedral specular reflector sorts photons by energy onto seven subcells; the paper reports:
Experimental (Eisler 2019, IEEE JPV): 7 subcells, 88% optical splitting efficiency, >50% total module efficiency measured.
Formalized structural monotonicity: under the record model, adjoining a zero-power band to an N-band module cannot decrease efficiency. The sharper thermodynamic multijunction bound (optimal N+1 ≥ optimal N; DeVos 1980, Martí & Araújo 1996) is standard and is not formalized here.
The blackbody flux above any bandgap is proved strictly decreasing in Eg. The proof: the Wien function f(x) = (x² + 2x + 2)·e−x loses to exponential decay because 1 + h + h²/2 ≤ eh. Foundation for Stokes shift concentration.
Every photon that enters the module must first cross a dielectric interface. The loss is set by Fresnel—drag the sliders and watch Rs, Rp, and the unpolarized average evolve. Brewster's angle is the zero of the p-curve.
Eisler/Thermodynamics/ · 29 theorems