Full visible waveband tunable formamidinium halides hybrid perovskite QDs via anion-exchange route and their high luminous efficiency LEDs.

Colloidal hybrid perovskite quantum dots (QDs) of formamidinium lead halides (FAPbX 3 , X = Cl, Br, I and their mixture), which possess a full visible waveband tunable photoluminescence ranging from 429 nm to 782 nm verified by the calculated bandgap of FAPbX 3 (2.720eV–2.115eV–1.401eV; from Cl to Br to I) , have been prepared by regulating the halogen in FAPbBr 3. Herein, the as-obtained FAPbX 3 QDs feature a high quantum yield up to 85% and narrow emission line-widths low to 20 nm, benefiting from the highly uniform cubic morphology. In addition, the mechanism of anion-exchange in FAPbX 3 QDs is expounded from two aspects of defects and temperature by theoretical calculation and experiment method. Trichromatic LEDs are fabricated to demonstrate the photoelectric properties by employing the FAPbX 3 QDs, which have a pure color and narrow full width at half maximum (FWHM, 20.6 nm for Blue, 22 nm for Green, 36.6 nm for Red, respectively). More interestingly, the green one reaches the Rec.2020 standard and the corresponding QD white LED presents a high luminous efficiency of 48.8 lm/w and color rendering index (CRI) 90.2 together with the CIE color coordinate at (0.32,0.31). • The FAPbX 3 QDs tuned from 429 nm to 782 nm are synthesized by anion-exchange. • The mechanisms of exchange process and the band structure are expounded. • The obtained QDs feature a high PLQY up to 85% and narrow FWHM low to 20 nm. • WLEDs are fabricated with high luminous efficiency (48.8 lm/w) and CRI (90.2). [ABSTRACT FROM AUTHOR]