Effect of Nonionic Surfactant Additive in PEDOT:PSS on PFO Emission Layer in Organic–Inorganic Hybrid Light-Emitting Diode

Poly­(9,9-dioctylfluorene) (PFO) has attracted significant interests owing to its versatility in electronic devices. However, changes in its optical properties caused by its various phases and the formation of oxidation defects limit the application of PFO in light-emitting diodes (LEDs). We investigated the effects of the addition of Triton X-100 (hereinafter shortened as TX) in poly­(3,4-ethylenedioxythiophene):poly­(styrenesulfonate) (PEDOT:PSS) to induce interlayer diffusion between PEDOT:PSS and PFO to enhance the stability of the PFO phase and suppress its oxidation. Photoluminescence (PL) measurement on PFO/TX-mixed PEDOT:PSS layers revealed that, upon increasing the concentration of TX in the PEDOT:PSS layer, the β phase of PFO could be suppressed in favor of the glassy phase and the wide PL emission centered at 535 nm caused by ketone defects formed by oxidation was decreased considerably. LEDs were then fabricated using PFO as an emission layer, TX-mixed PEDOT:PSS as hole-transport layer, and zinc oxide (ZnO) nanorods as electron-transport layer. As the TX concentration reached 3 wt %, the devices exhibited dramatic increases in current densities, which were attributed to the enhanced hole injection due to TX addition, along with a shift in the dominant emission wavelength from a green electroluminescence (EL) emission centered at 518 nm to a blue EL emission centered at 448 nm. The addition of TX in PEDOT:PSS induced a better hole injection in the PFO layer, and through interlayer diffusion, stabilized the glassy phase of PFO and limited the formation of oxidation defects

High-Performance Green Light-Emitting Diodes Based on MAPbBr₃–Polymer Composite Films Prepared by Gas-Assisted Crystallization

The morphology of perovskite films has a significant impact on luminous characteristics of perovskite light-emitting diodes (PeLEDs). To obtain a highly uniform methylammonium lead tribromide (MAPbBr₃) film, a gas-assisted crystallization method is introduced with a mixed solution of MAPbBr₃ precursor and polymer matrix. The ultrafast evaporation of the solvent causes a high degree of supersaturation which expedites the generation of a large number of nuclei to form a MAPbBr₃–polymer composite film with full surface coverage and nano-sized grains. The addition of the polymer matrix significantly affects the optical properties and morphology of MAPbBr₃ films. The PeLED made of the MAPbBr₃–polymer composite film exhibits an outstanding device performance of a maximum luminance of 6800 cd·m^–2 and a maximum current efficiency of 1.12 cd·A^–1. Furthermore, 1 cm² area pixel of PeLED displays full coverage of a strong green electroluminescence, implying that the high-quality perovskite film can be useful for large-area applications in perovskite-based optoelectronic devices