Fig. 2: The schematics represent an arbitrary narrow bandgap semiconductor with the distribution of charge carriers in the two energy bands (VB and CB) and efficiencies of various new generation solar cells which crosses the S-Q limit.

a The sequential process of HC, starting from excitation till recombination. b The cooling of HC in their respective bands of unequal curvatures (as different carrier effective mass). c The new generation solar cells with efficiency above the S–Q limit. d Under irradiation of 1 and 100 suns concentration (i.e., low-concentrator photovoltaics) the ultimate efficiency of HC solar cells, at different charge carrier temperatures, plotted versus their photoabsorber bandgap. A conventional solar cell is represented by the lowermost curve, while the vertical dashed lines correspond to the bandgap of halide perovskite materials. “A” in ASnI3 and APbI3 corresponds to methylammonium (MA), formamidinium (FA), and cesium (Cs) ions. The figures are adopted with permission from (a, b) ref. 14 and (c, d) ref. 26