Highly effective surface defect passivation of perovskite quantum dots for excellent optoelectronic properties

Abstract

Metal halide perovskite quantum dots (QDs) are next-generation materials with excellent optical and electrical properties suitable for display applications. However, their significantly large surface-area-to-volume ratio makes them highly susceptible to surface defects. In this study, we developed an effective passivation strategy that uses various imide derivatives (namely, caffeine, 4-amino-N-methylphthalimide, and 6-amino-1,3-dimethyluracil) to synthesize high-performance perovskite QDs. Caffeine or 6-amino-1,3-dimethyluracil significantly improved the optical properties and thermal stability by passivation of under-coordinated Pb2+ ions of the perovskite QDs. Moreover, these aided the removal of black dots that act as trap states, thereby yielding pure crystals. In contrast, 4-amino-N-methylphthalimide passivation led to deterioration of the optical properties and poor crystal purity because of its intrinsic impurities (black dots). Molecular calculations confirmed that the atomic charge of the carbonyl oxygen of the imide derivatives was proportional to the efficacy of passivation. The caffeine-passivated perovskite QDs were used to fabricate red, green, and blue light-emitting diodes. The current and external quantum efficiencies of these devices were significantly improved compared to those of the devices with pristine perovskite QDs. The color coordinate values of the fabricated devices showed an ultra-wide color gamut of 130% National Television System Committee.

Keywords

• Perovskite
• Defects
• Passivation
• Atomic charge
• Thermal stability
• Optoelectronic property