The future is blue (LEDs): why chemistry is the key to perovskite displays

In this Perspective, we review the recent work on metal halide perovskite light-emitting devices (peLEDs) with a focus on current challenges and the prospect of commercialization of perovskite displays. Metal halide perovskites have shown remarkable hole and electron mobilities, high photoluminescence quantum yield and color tunability, and thin line width emission peaks making them ideal materials for the emissive layer in LEDs. Red- and green-emitting perovskites have already achieved very high external quantum efficiencies of greater than 20% in the last year and may be ready to begin the commercialization process. However, blue peLEDs still lag behind in efficiency and stability. After reviewing recent attempts to improve the blue peLED efficiency, we then list the current challenges in the field and suggest possible avenues of future research, including improvements in materials chemistry and device architecture. In particular, we find that advancements are needed in color stability and lifetime, by using doping and nanostructured materials to avoid ion migration effects, and in the synthesis of novel compounds. We then compare the current state of the art in peLEDs with the competitive landscape and conclude that fixing the blue peLEDs is the key to building micropixel LEDs from perovskites. Without blue-emitting perovskites, high PLQY perovskite films can still be useful for down-conversion color filters but may have difficulty displacing existing technologies. Thus, for perovskites, the future is indeed blue (LEDs).