Perovskite energy funnels for efficient light-emitting diodes.
Research paper by
Mingjian M Yuan, Li Na LN Quan, Riccardo R Comin, Grant G Walters, Randy R Sabatini, Oleksandr O Voznyy, Sjoerd S Hoogland, Yongbiao Y Zhao, Eric M EM Beauregard, Pongsakorn P Kanjanaboos, Zhenghong Z Lu, Dong Ha DH Kim, Edward H EH Sargent
Organometal halide perovskites exhibit large bulk crystal domain sizes, rare traps, excellent mobilities and carriers that are free at room temperature-properties that support their excellent performance in charge-separating devices. In devices that rely on the forward injection of electrons and holes, such as light-emitting diodes (LEDs), excellent mobilities contribute to the efficient capture of non-equilibrium charge carriers by rare non-radiative centres. Moreover, the lack of bound excitons weakens the competition of desired radiative (over undesired non-radiative) recombination. Here we report a perovskite mixed material comprising a series of differently quantum-size-tuned grains that funnels photoexcitations to the lowest-bandgap light-emitter in the mixture. The materials function as charge carrier concentrators, ensuring that radiative recombination successfully outcompetes trapping and hence non-radiative recombination. We use the new material to build devices that exhibit an external quantum efficiency (EQE) of 8.8% and a radiance of 80 W sr(-1) m(-2). These represent the brightest and most efficient solution-processed near-infrared LEDs to date.