(a) Evolution of best researched solar cells’ efficiency comparing Si to lead halide perovskites (data adopted from National Renewable Energy Laboratory (NREL)). Recent published results for lead-free double perovskite cells Cs2AgBiBr6 state 2.2% efficiency.94 Owing to their high PLQYs, narrow PL FWHM, and tunability over the entire visible spectral range, lead halide perovskites nanocrystals can find applications in (b) PL down conversion, as used in LCD displays and lighting, (c) electroluminescent devices such as LEDs, and (d) solar cells. Reprinted with permission from Macmillan Publishers, Nature Materials,95 copyright (2018).