Making semiconductor diodes that emit blue light has always been a challenge
Since halide perovskites first drew wide attention in 2009, when Japanese scientists discovered that they make highly efficient solar cells, these easily made, inexpensive crystals have excited researchers. So far, red- and green-emitting diodes have been demonstrated, but not blue. Halide perovskite blue-emitting diodes have been unstable — that is, their color shifts to longer, redder wavelengths with use. As Yang and his colleagues discovered, […]