Blue-Green Luminescence from CsPbX3 perovskite nanocrystals (X = Br, Cl, Br/Cl)

Abstract

CdSe based traditional colloidal quantum dots (cQDs) are well known for their photoluminescence (PL) properties. Last year, colloidal CsPbBr3 nanocrystals (NCs), that has nearly ideal quantum yield (QY) of ~90% with narrow (FWHM = 85 meV) spectral width was reported. Later, it was demonstrated that CsPbBr3 NCs have less influence of self-absorption and Förster resonance energy transfer (FRET). Furthermore, they exhibit no change in the PL peak position in the temperature range of 25 oC to 100 oC. But these properties were mainly established for emission with peak at 511 nm. The motive of my work is to extend the emission range to lower wavelengths without compromising on these exciting properties. Size-dependent tuning of the emission wavelengths is inhibited for CsPbBr3 NCs as it doesn’t lie in quantum confinement (QC) regime. So, tuning can be achieved by compositional modulation of CsPbX3 (X = Cl, Br, I or Cl/Br, Br/I) NCs. Surprisingly, colloidal CsPbX3 (X = Br, Cl, Br/Cl) NCs show either no change or a slight blue shift (upto 2-3 nm) in the PL peak position with variation of temperature from 20 oC to 80 oC. Interestingly, a high PL QY (55-80%) along with narrow FWHM (75-95 meV) is obtained in blue-green emission with PL peak ranging between 465 to 515 nm. It is to be noted that achieving high PL QY for blue emitting QDs have been an outstanding problem for a long time. Another important aspect is that the PL decay dynamics of CsPbX3 NC films show similar decay at all emission energies, which suggest less influence of FRET in chromaticity.