Deep-red light-emitting electrochemical cells based on phosphor-sensitized thermally activated delayed fluorescence

Abstract

Solid-state light-emitting electrochemical cells (LECs) show the advantages of simple fabrication process, low-voltage operation, and compatibility with inert electrodes. However, even phosphorescent deep-red LECs still suffer from limited device efficiencies....

Long‐Wavelength Light‐Emitting Electrochemical Cells: Materials and Device Engineering

“…Recently reported phosphorescent-sensitized TADF deep red LECs based on an iTMC host and a TADF deep-red small-molecule guest realized phosphorescent EL efficiency from a fluorescent emissive material. [99] This strategy takes advantages of well-developed iTMCs with good superior carrier balance and high EL efficiency. In addition, commercially available efficient deep-red and NIR TADF small molecules can be used in this system, offering better EL color tunability.…”

“…9) with thermally activated delayed fluorescence (TADF) as the guest. [99] Owing to the small singlet-triplet energy splitting (ΔE ST ) of 0.14 eV, [100] the NIR TADF compound APDC-DTPA exhibits effective reverse intersystem crossing (RISC) process [101] to recycle the guest triplet excitons. As such, the proposed NIR LECs based on phosphorescent-sensitized TADF showed a promising EQE > 5 % under a lower guest doping concentration (0.25 wt.%) and a lower device current.…”

“…To further enhance the device performance, Chen et al. utilized the iTMC [Ir(bppz) 2 (dphen)][PF 6 ], where bppz is butylphenylpyrazole and dphen is 4,7‐diphenyl‐1,10‐phenanthroline, as the host and replaced the cyanine dye with the compound 3,4‐bis(4‐(diphenylamino)phenyl)acenaphtho[1,2‐ b ]pyrazine‐8,9‐dicarbonitrile ( APDC‐DTPA , compound 84 , Figure 9) with thermally activated delayed fluorescence (TADF) as the guest [99] . Owing to the small singlet‐triplet energy splitting (Δ E ST ) of 0.14 eV, [100] the NIR TADF compound APDC‐DTPA exhibits effective reverse intersystem crossing (RISC) process [101] to recycle the guest triplet excitons.…”

Deep-red and near-infrared light-emitting electrochemical cells employing perovskite color conversion layers with EQE >10%

“…All bluegreen LECs on diffusive substrates integrated with perovskite CCLs showed peak EQEs higher than 10%, which are among the highest reported values for the deep-red and NIR LECs based on any types of emissive materials. [15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][52][53][54][55][56][57][58]61 Making use of inorganic perovskite CCLs successfully overcomes the difficulties of moderate emission efficiencies of longwavelength organic emissive materials due to the energy-gap law. Energy down-conversion via red CCLs has been This journal is © The Royal Society of Chemistry 2022 demonstrated to realize highly efficient white LECs.…”

Dinuclearization strategy of cationic iridium(iii) complexes for efficient and stable flexible light-emitting electrochemical cells

“…[15][16][17] As a result, the efficiencies of LECs have been significantly improved, especially for those based on the ionic transition metal complexes (iTMCs) with the efficient spin-orbit coupling effect. [18][19][20] Despite the advanced achievement in the EL efficiency and color control from visible to near-infrared emission, the ligand-exchange reactions caused by the foreign species usually lead to poor operational stability of the iTMCs-based LECs, which needs to be solved for practical applications. 21 Therefore, it remains a considerable challenge to balance the trade-off between the device efficiencies and stabilities.…”