Synergistic Regulation Effect of Nitrate and Calcium Ions for Highly Luminescent and Robust α-CsPbI3 Perovskite

The alpha-CsPbI3 nanocrystals (NCs) easily transform into yellow non-perovskite, accompanying with declining photoelectric properties that restricting their practical applications in diverse fields. Herein, the highly luminescent and robust alpha-CsPbI3 NCs is achieved through engineering the lattice symmetry of perovskite, enabled by the synergistic effect of NO3- ion passivation and Ca2+ ion doping. The introduced NO3- ions enhance the phase-change energy barrier and the surface steric hindrance, thus promoting the formation of alpha-CsPbI3 NCs with hyper-symmetric crystal structure, while the Ca2+ ion doping contributes to improving their lattice symmetry by significant regulation of the tolerance factor. As a result, the obtained alpha-CsPbI3 NCs display an outstanding photoluminescence quantum yield of 96.6%, together with the reduced defect state density and eminent conductivity. Most importantly, the as-engineered alpha-CsPbI3 NCs exhibit excellent stability under ambient conditions for 9 months and UV illumination for 32 h. It displays brilliant thermal stability, maintaining luminous intensity for 15 min under 140 degrees C, and performing desired durability and reversibility, evidenced by 160 degrees C cyclic test and 120 degrees C reversibility test. Given enhanced robustness, the as-engineered alpha-CsPbI3 NCs based lightemitting-diode devices are constructed, exhibiting a power efficiency of 105.3 Im W-1 and the excellent working stability for 18 h.

Automated summary

By engineering the lattice symmetry of perovskite and combining NO3- ion passivation and Ca2+ ion doping, highly luminescent and robust alpha-CsPbI3 nanocrystals with excellent stability, photoluminescence quantum yield, and conductivity are obtained. These nanocrystals are suitable for use in light-emitting diode devices.