Zn-Alloyed CsPbI₃ Nanocrystals for Highly Efficient Perovskite Light-Emitting Devices

We alloyed Zn²⁺ into CsPbI₃ perovskite nanocrystals by partial substitution of Pb²⁺ with Zn²⁺, which does not change their crystalline phase. The resulting alloyed CsPb_0.64Zn_0.36I₃ nanocrystals exhibited an improved, close-to-unity photoluminescence quantum yield of 98.5% due to the increased radiative decay rate and the decreased non-radiative decay rate. They also showed an enhanced stability, which correlated with improved effective Goldschmidt tolerance factors, by the incorporation of Zn²⁺ ions with a smaller radius than the Pb²⁺ ions. Simultaneously, the nanocrystals switched from n-type (for CsPbI₃) to nearly ambipolar for the alloyed nanoparticles. The hole injection barrier of electroluminescent LEDs was effectively eliminated by using alloyed CsPb_0.64Zn_0.36I₃ nanocrystals, and a high peak external quantum efficiency of 15.1% has been achieved.