Large-scale room-temperature synthesis of high-efficiency lead-free perovskite derivative (NH4)2SnCl6:Te phosphor for warm wLEDs

Abstract

• Perovskite (NH 4 ) 2 Sn 1-x Te x Cl 6 phosphors were developed for solid-state lighting. • The phosphors show broad orange emission with high PLQY (FWHM: 127 nm; PLQY: 84%). • The structure–property relations were revealed. • The excellent warm wLED was created using the title phosphors. Low-dimensional lead-based perovskite materials have recently attracted extensive attentions for their diverse structures, unique optoelectronic properties and enhanced stability. However, the toxicity of lead, low photoluminescence quantum yield (PLQY) and complex preparation processes limit their practical applications. Herein, we present a simple room-temperature synthesis of orange-emitting lead-free perovskite derivative (NH 4 ) 2 SnCl 6 :Te phosphors with a large quantity at one time. By introducing Te 4+ ions with 5s 2 active lone pairs, (NH 4 ) 2 SnCl 6 :Te exhibits broadband emission peaked at 590 nm, a large full width at half maximum (FWHM) about 127 nm and a maximum PLQY up to 83.51%. Density functional theory calculations combined with comprehensive spectroscopic data reveal that the incorporated Te 4+ ions change the band structure and trigger the formation of Jahn-Teller-like self-trapped excitons (STEs) in [TeCl 6 ] 2− centers. In addition, (NH 4 ) 2 SnCl 6 :Te shows excellent ambient and thermal stabilities. Using (NH 4 ) 2 SnCl 6 :0.5%Te as an orange down-conversion material, highly stable wLEDs with a Commission Internationale de l’Eclairage (CIE) of (0.39, 0.38), correlated color temperature (CCT) of 3855 K, and color rendering index (CRI) of 83 are demonstrated. We expect these results to facilitate the development of low-cost, environmentally friendly and high-performance novel phosphors for future lighting and display technologies.