Abstract
α-CsPbI3 nanocrystals (NCs) with poor stability prevent their wide applications in optoelectronic fields. Ca2+ (1.00 Å) as a new B-site doping ion can successfully boost CsPbI3 NC performance with both improved phase stability and optoelectronic properties. With a Ca2+/Pb2+ ratio of 0.40%, both phase and photoluminescence (PL) stability could be greatly enhanced. Facilitated by increased tolerance factor, the cubic phase of its solid film could be maintained after 58 days in ambient condition or 4 h accelerated aging process at 120°C. The PL stability of its solution could be preserved to 83% after 147 days in ambient condition. Even using UV light to accelerate aging, the T50 of PL could boost 1.8-folds as compared to CsPbI3 NCs. Because Ca2+ doping can dramatically decrease defect densities of films and reduce hole injection barriers, the red light-emitting diodes (LEDs) exhibited about triple enhancement for maximum the external quantum efficiency (EQE) up to 7.8% and 2.2 times enhancement for half-lifetime of LED up to 85 min. We believe it is promising to further explore high-quality CsPbI3 NC LEDs via a Ca2+-doping strategy.
Highlights
All-inorganic perovskite (CsPbX3, X = Cl, Br, I) nanocrystals (NCs) have the potential to promote the development of the luminescence and display industry due to their high photoluminescence quantum yields (PLQYs), high color purity, and solution processability [1,2,3,4,5,6,7,8,9,10,11]
Ca2+-doped CsPbI3 NC-based light-emitting diodes (LEDs) exhibited about triple enhancement for maximum external quantum efficiency (EQE) up to 7.8%, and 2.2 times enhancement for half-lifetime of LED up to 85 min
Ca2+-doped CsPbI3 NC solid films could maintain the cubic phase after 58-day storage in ambient condition or 4 h accelerated aging process at 120°C
Summary
According to the Goldschmidt tolerance factor (τ) function for perovskite (ABX3), doping ions with suitable size can realize precise tuning of τ to stabilize cubic phase [23, 24]. Based on this principle, A-, B-, or X-site doping can maintain α-CsPbI3. It should be noted that the size of Sr2+ (1.18 Å) is almost the same as Pb2+ (1.19 Å) In other words, both stability and optoelectronic performance have more room to improve by doping other small size alkaline earth metal ions, such as Ca2+ (1.00 Å). We explored Ca2+ as a new B-site doping ion to boost CsPbI3 stability and NC performance with both improved phase optoelectronic properties. We believe it is promising to further explore high-quality CsPbI3 NC LED via Ca2+-doping strategy
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