Advanced red phosphors for white light-emitting diodes

White light-emitting diodes (WLEDs) with high luminous brightness, low energy consumption, long lifetime and environmental friendliness can be applied in various fields. However, low colour rendering index and high correlated colour temperature have seriously limited the quality of white light, resulting from the deficiency of the red light component in commercial phosphors. New phosphors that can emit suitable red light are needed. The improvement of red emitters has gradually become a hot topic in WLED applications such as good colour rendering lighting and full colour displays. This review summarizes recent achievements concerning red phosphors mainly from three aspects. They are: intensifying absorption bands and reducing lattice defects to increase quantum efficiency; selecting an appropriate coordination environment and altering the lattice symmetry to fine-tune the luminescence spectra; and reducing the nonradiative transition rate and preventing charge imbalance of a luminescence centre to enhance thermal stability.