Efficient and chromaticity stable green and white organic light-emitting devices with organic–inorganic hybrid materials

Efficient inverted bottom emissive organic light emitting diodes (IBOLEDs) with tin dioxide and/or Cd-doped SnO(2) nanoparticles as an electron injection layer at the indium tin oxide cathode:electron transport layer interface have been fabricated. The SnO(2) NPs promote electron injection efficiently because their conduction band (−3.6 eV) lies between the work function (W(f)) of ITO (4.8 eV) and the LUMO of the electron-transporting molecule (−3.32 eV), leading to enhanced efficiency at low voltage. The 2.0% SnO(2) NPs (25 nm) with Ir(ddsi)(2)(acac) emissive material (SnO(2) NPs/ITO) have an enhanced current efficiency (η(c), cd A(−1)) of 52.3/24.3, power efficiency (η(p), lm W(−1)) of 10.9/3.4, external quantum efficiency (η(ex), %) of 16.4/7.5 and luminance (L, cd m(−2)) of 28 182/1982. A device with a 2.0% Cd-doped SnO(2) layer shows higher η(c) (60.6 cd A(−1)), η(p) (15.4 lm W(−1)), η(ex) (18.3%) and L (26 858 cd m(−2)) than SnO(2) devices or control devices. White light emission was harvested from a mixture of Cd–SnO(2) NPs and homoleptic blue phosphor Ir(tsi)(3); the combination of blue emission (λ(EL) = 428 nm) from Ir(tsi)(3) and defect emission from Cd–SnO(2) NPs (λ(EL) = 568 nm) gives an intense white light with CIE of (0.31, 0.30) and CCT of 6961 K. The white light emission [CIE of (0.34, 0.35) and CCT of 5188 K] from colloid hybrid electrolyte BMIMBF(4)–SnO(2) is also discussed.