CH₃NH₃Pb_1–<i>x</i>Co<i>_x</i>Br_{3–2<i>x</i>}Cl_2<i>x</i> Perovskite Quantum\nDots for Wide-Color Backlighting

Abstract

In\nrecent years, perovskite quantum dots (PQDs) with the incorporation\nof transition-metal ions for reducing toxicity and enhancing stability\nhave been in a research hotspot. However, the PQDs containing transition-metal\nions are quite unstable and display low photoluminescence quantum\nyields (PLQYs), owing to the existence of defects. Herein, we have\nendeavored to introduce simultaneous cation and anion exchange with\ncobalt and chloride ions into the host CH₃NH₃Pb_1–<i>x</i>Co<i>_x</i>Br_{3–2<i>x</i>}Cl_2<i>x</i> PQDs followed by matrix encapsulation via poly­(methyl methacrylate)\n(PMMA) as a favorable approach to stabilize PQDs with improved PLQY.\nWe have utilized cobalt chloride as the precursor for doping ions.\nThe emission wavelength can be regulated from green to cyan color\nwith the increase in doping concentration without negotiating on color\nquality, which is believed to be the modification of band gap and\ncorresponding electron density estimated from the density functional\ntheory. A high PLQY of 95% is observed even after the incorporation\nof cobalt and chloride ions into host PQDs. We demonstrate white light-emitting\ndiode (LED) prototypes for backlight applications using a PQDs/PMMA\ncomposite on a blue LED chip, which exhibits excellent stability toward\nan ambient and robust atmosphere and provides a wide-color gamut of\n124% of the NTSC standard. This research paves a way for the research\ncommunity to synthesize highly efficient, color-tunable PQDs for wide-color\nbacklighting applications.