Bright Red YCl3-promoted CsPbI3 Perovskite Nanorods Towards Efficient Light-Emitting Diode

Abstract One-dimensional (1D) CsPbI3 nanorods (NRs) possess the suitable bandgap, extinction coefficient, long exciton diffusion radius and directed conductive channel, which make them advantageous for numerous optoelectronic devices. However, the direct synthesis of high-quality CsPbI3 NRs remains a challenge. Here, we develop a direct and facile synthetic approach to prepare the CsPbI3 NRs by YCl3 promotion. The YCl3 is not only the inducement of anisotropic growth of NCs, but also the source of passivator for improving the stability of NCs. Because of an effective YCl3 passivation, the efficient red emitting CsPbI3 NCs with photoluminescence quantum yield (PLQY) of 97% was achieved. More importantly, the YCl3 promoted CsPbI3 NRs with small aspect ratio of ~3.2 exhibit the PLQY of 84%, the highest value obtained from the red perovskite NRs. The fluorescence anisotropy of 0.184 mmol-YCl3 promoted CsPbI3 NRs is 0.38, and the rotational diffusion time τ rot =1000 ns. The analysis on fluorescence anisotropy of the CsPbI3 perovskite NRs proves that the size in length and width is consistent with the result measured by TEM images of as-prepared perovskite NRs. Meanwhile, conductivities of the films made of 0.184 mmol-YCl3 promoted CsPbI3 NRs is 2.94 ×10-1 S/cm, which is 17 times higher than 1.70 × 10-2 S/cm of bare CsPbI3 nanocubes. Furthermore, various CsPbI3 NCs are employed to prepare light-emitting diodes (LEDs). The YCl3 promoted CsPbI3 NRs based LEDs display an optimum external quantum yield (EQE) of 10.5%, and luminance of 1672 cd/m2. These results prove that the as-prepared YCl3 promoted CsPbI3 NRs have promising prospect in optoelectronic devices.