High-performance Green Light-emitting Diodes Research Articles

Short-branched alkyl sulfobetaine-passivated CsPbBr3 nanocrystals for efficient green light emitting diodes.

Inorganic cesium lead bromide nanocrystals (CsPbBr3 NCs) hold promising prospects for high performance green light-emitting diodes (LEDs) due to their exceptional color purity and high luminescence efficiency. However, the common ligands employed for passivating these indispensable NCs, such as long-chain organic ligands like oleic acid and oleylamine (OA/OAm), display highly dynamic binding and electronic insulating issues, thereby resulting in a low efficiency of the as-fabricated LEDs. Herein, we report a new zwitterionic short-branched alkyl sulfobetaine ligand, namely trioctyl(propyl-3-sulfonate) ammonium betaine (TOAB), to in situ passivate CsPbBr3 NCs via a feasible one-step solution synthesis, enabling efficiency improvement of CsPbBr3 NC-based LEDs. The zwitterionic TOAB ligand not only strengthened the surface passivation of CsPbBr3 NCs with a high photoluminescence quantum yield (PLQY) of 97%, but also enhanced the carrier transport in the fabricated CsPbBr3 NC thin films due to the short-branched alkyl design. Consequently, CsPbBr3 NCs passivated with TOAB achieved a green LED with an external quantum efficiency (EQE) of 7.3% and a maximum luminance of 5716 cd m-2, surpassing those of LEDs based on insulating long-chain ligand-passivated NCs. Our work provides an effective surface passivation ligand design to enhance the performance of CsPbBr3 NC-based LEDs.

Green light-emitting diode from bromine based organic-inorganic halide perovskite

Organic-inorganic halide perovskites have attracted considerable attention owing to their outstanding solar cell efficiency. Meanwhile, these halide perovskites exhibit good light emitting in visible and near-infrared range with high fluorescence quantum yield, resulting in electroluminescence. However, it remains challenging for lighting and display due to the low luminance and poor long-term stability. Herein, high performance green light-emitting diodes are fabricated from bromine based perovskite (CH3NH3PbBr3) by systematically adjusting the preparation conditions and optimizing the emitting layer thickness. A high luminance up to 1500 cd m−2 (one of the highest values for perovskites-based light-emitting diodes) was achieved with 80 nm perovskites-emitting layer, due to the well-crystallized, full-coverage property of the films. This result further confirms the great prospect of organic-inorganic perovskites in optoelectronics.