Fig. 2

Material designs for efficient QLEDs. a Photograph of solutions containing CdSe QDs of various sizes, showing emission color covering the entire visible light range. b Spectral range of QDs with various semiconductor materials. c PL spectra of CdSe/ZnS and PbS/CdS core/shell QDs. d CIE chromaticity diagram showing the color gamut of CdSe QDs in comparison with that of conventional high-definition television standards. e Scheme showing the band structure of core/shell heterojunctions. f Scheme comparing the carrier dynamics of core/shell QDs with thick and thin shells. g Time-resolved PL spectra of QDs under various conditions. The inset shows the change in the carrier lifetime as a function of applied voltage. h Comparison of EQEs of QLEDs with CdSe/CdS core/shell QDs and CdSe/CdS/Zn_0.5Cd_0.5S core/shell/shell QDs. i, j, Current density–luminance–voltage characteristics (i), current efficiency and EQE (j) of QLEDs using CdSe/ZnS QDs with CdS-rich (blue) and ZnSe-rich (red) intermediate shells. k Energy band diagram, schematic, and TEM images of double heterojunction nanorods. l Current and power efficiencies of QLEDs based on double heterojunction nanorods as a function of luminance. The inset show a photograph comparing double heterojunction nanorod QLEDs and conventional core/shell QLEDs. m Energy diagram of InP@ZnSeS QLEDs. n EL spectrum and photograph of flexible InP@ZnSeS QLEDs on a polyethersulfone substrate. o TEM images and corresponding schematic images of Cu–In–S/ZnS QDs with controlled shell thickness. p EL spectra and corresponding images of Cu–In–S/ZnS QLEDs as a function of applied voltage. Figure reproduced with permission from: a ref. ²⁵ © 2010 Wiley; c ref. ²⁶ © 2010 Nano Reviews; f ref. ⁴⁶ © 2012 NPG; g, h ref. ⁴⁷ © 2013 NPG; i, j ref. ⁵² © 2015 NPG; k ref. ⁵³ © 2014 NPG; l ref. ⁵⁴ © 2015 ACS; m, n ref.⁶⁹ © 2013 ACS; o, p ref. ⁷³ © 2016 ACS