Blue Emissive Light Emitting Diodes Using ZnO-Graphene Oxide (GO) and ZnO-Polyaromatic Hydrocarbons Hybrid Quantum Dots

A self-emissive electroluminescent quantum dots (ELQDs) LED display is highly expected as a next generation flexible display. are highly demanded for achieving eco-friendly ELQDs. Ecofriendly ZnO semiconductors has a band gap of 3.37 eV and large exciton binding energy (~60 meV) at RT and thus expected to be good candidates for non-harmful Cd and inexpensive In-free blue QDs. ZnO QDs are hybridized with graphene oxide QDs (GO) [1] and functionalized poly-aromatic hydrocarbonds (f-PAHs) [2] to control the intrinsic defects located on ZnO surfaces causing green emission. From time-resolved PL (TRPL) for ZnO and ZnO-GO QDs reveals that conventional green emission of ZnO QDs has a longer lifetime by 10³ times than ~ns of blue emission and disappear by hybridization with GO. Type I ZnO-GO QLEDs show deep-blue electroluminescence (EL) at 438 nm, brightness of 1980 cd m^-2, and an external quantum efficiency (EQE) of 2.78% with CIE (0.16, 0.11) without green emission. In a similar way, quasi type II ZnO/1-aminopyrene hybrid QDs-based QLEDs show EL of 3379 cd m^-2 at λ = 441 nm with a full width at half maximum of 41.7 nm, a luminous efficacy (LE) of 3.32 cd/A, EQE of 2.35%, and remarkably long lifetime T₅₀ of &gt;17830 h at 100 cd/m².<br/><br/>[1] H.H Kim et al. ACS Photonics, 7 (2020) 723-734.<br/>[2] H.H. Kim, S. Park, H. Lee, J.K. Kang, W.K. Choi, Adv. Opt. Mater. (2022) 2200601.