Researchers from Kyushu University have developed highly efficient organic light-emitting diodes (OLEDs) using a new class of molecules called "Hyper-fluorescence." These molecules, based on carbazolyl dicyanobenzene (CDCB), enable efficient thermally-activated delayed fluorescence (TADF) with high photoluminescence efficiency. The key innovation is the design of molecules that minimize the energy gap between singlet and triplet excited states, promoting efficient spin-up conversion from triplet to singlet states (reverse intersystem crossing, or reverse ISC), while maintaining a high radiative decay rate. This results in a high fluorescence efficiency of over 90% and an external EL efficiency of over 19%, comparable to phosphorescent OLEDs. The study demonstrates that CDCB molecules can emit light through both singlet and triplet excitons, achieving a new luminescence concept called "Hyper-fluorescence." The molecules were synthesized through a simple one-step reaction using commercially available materials, avoiding the need for rare metals. The synthesized CDCB molecules showed high thermal stability and efficient photoluminescence, with a high PL quantum yield (PLQY) and minimal Stokes shift. The molecules also exhibited a wide range of emission colors, from sky-blue to orange, by varying the electron-donating and electron-accepting abilities of their peripheral groups. The OLEDs based on CDCB derivatives achieved high external EL quantum efficiencies, with the green OLED reaching 19.3% and the orange and sky-blue OLEDs achieving 11.2% and 8.0%, respectively. These results demonstrate the potential of CDCB-based materials for high-efficiency OLEDs without the need for heavy metals, which are typically required for phosphorescent materials. The study highlights the flexibility of organic molecules in achieving high efficiency through careful molecular design, opening new avenues for solid-state lighting and display applications.Researchers from Kyushu University have developed highly efficient organic light-emitting diodes (OLEDs) using a new class of molecules called "Hyper-fluorescence." These molecules, based on carbazolyl dicyanobenzene (CDCB), enable efficient thermally-activated delayed fluorescence (TADF) with high photoluminescence efficiency. The key innovation is the design of molecules that minimize the energy gap between singlet and triplet excited states, promoting efficient spin-up conversion from triplet to singlet states (reverse intersystem crossing, or reverse ISC), while maintaining a high radiative decay rate. This results in a high fluorescence efficiency of over 90% and an external EL efficiency of over 19%, comparable to phosphorescent OLEDs. The study demonstrates that CDCB molecules can emit light through both singlet and triplet excitons, achieving a new luminescence concept called "Hyper-fluorescence." The molecules were synthesized through a simple one-step reaction using commercially available materials, avoiding the need for rare metals. The synthesized CDCB molecules showed high thermal stability and efficient photoluminescence, with a high PL quantum yield (PLQY) and minimal Stokes shift. The molecules also exhibited a wide range of emission colors, from sky-blue to orange, by varying the electron-donating and electron-accepting abilities of their peripheral groups. The OLEDs based on CDCB derivatives achieved high external EL quantum efficiencies, with the green OLED reaching 19.3% and the orange and sky-blue OLEDs achieving 11.2% and 8.0%, respectively. These results demonstrate the potential of CDCB-based materials for high-efficiency OLEDs without the need for heavy metals, which are typically required for phosphorescent materials. The study highlights the flexibility of organic molecules in achieving high efficiency through careful molecular design, opening new avenues for solid-state lighting and display applications.