Spectrally Stable Deep-Blue Perovskite Light-Emitting Diodes Enabled by a Deep Eutectic Solvent

摘要

Full-color LED display requires Commission Internationale de l’Eclairage (CIE)1931 coordinates of (0.14, 0.08), based on the National Television StandardsCommittee (NTSC) blue standard. However, such deep-blue perovskitelight-emitting diodes (PeLEDs) still lag far behind in terms of device efficiency.Moreover, spectral stability remains a big challenge. To settle these issues, akind of deep eutectic solvent (DES) is introduced as the perovskite precursorsolvent additive, which is formed from a hydrogen bond acceptor (HBA)choline chloride and a hydrogen bond donor (HBD) urea via the hydrogenbond interaction. The incorporation of DES has multiple advantages, shownas follows: 1) improves the solubility of CsCl to yield dense perovskitemorphology, 2) inhibits the growth of the perovskite crystal to achieve low-nphases with narrow distribution, and 3) stabilizes the halide anions in thelattice to ensure stable electroluminescence (EL) spectra. As a result, theas-prepared PeLED shows the maximum external quantum efficiency(EQE_(max)) of 2.71% with a CIE coordinate of (0.134, 0.055). With the increasein the DES concentration, the spectra stability is also obviously enhanced.