Organic-inorganic hybrid composites as an electron injection layer in highly efficient inverted green-emitting polymer LEDs

Optimizing Interfacial Energetics for Conjugated Polyelectrolyte Electron Injection Layers in High Efficiency and Fast Responding Polymer Light Emitting Diodes

“… 3 CPEs can also reduce luminescence quenching in PLEDs such as by reducing image charge quenching from metal interfaces 14 , 15 and passivating quenching states in metal oxides. 16 , 17 However, CPEs themselves are poor emitters with the ions known to quench luminescence. 18 Other sources of quenching include chemical defects of the emitting layer 19 and solid state concentration quenching.…”

“…Recently, CPEs have found use as interlayer materials in organic optoelectronic devices. − In particular, thin (5–20 nm) CPE electron injection layers (EILs) have been found to greatly enhance electron injection from high workfunction electrodes into polymer light-emitting diodes (PLEDs) and improve device efficiency. ,,− This allows CPEs to replace traditional low workfunction metals that are both less stable and less environmentally friendly . CPEs can also reduce luminescence quenching in PLEDs such as by reducing image charge quenching from metal interfaces , and passivating quenching states in metal oxides. , However, CPEs themselves are poor emitters with the ions known to quench luminescence . Other sources of quenching include chemical defects of the emitting layer and solid state concentration quenching …”

“…One of the drawbacks of using CPEs as EILs in PLEDs is the aforementioned rearrangement of the counterions following application of an electric field across the device as this can significantly increase the response times in PLEDs to a few seconds, which is too slow for display purposes where fast switching is required. ,, Previous literature has focused on modifying the size and structure of the counterions, whereby large ions (such as tetrakis­(1-imidazolyl)­borate (BIm 4 ) anions) are exchanged for smaller halide ions (such as F – ions) to improve device response. The smaller ions are less disruptive to chain packing and can be transported faster, although even with this change, response times remain too long. , Other methods to improve device response include synthesis of zwitterionic CPEs where both cation and anion groups are tethered to the conjugated backbone. − Blending CPEs with zinc oxide nanoparticles has also been shown to improve device response times . Modification of the conjugated backbone structure of CPEs has been another strategy but has previously produced mixed results; incorporating benzothiadiazole units into otherwise fluorene backbones has succeeded in increasing PLED device performance in some cases, while in others it has led to drastically reduced device performance, the reasons for which are poorly understood. , …”

“…36−38 Blending CPEs with zinc oxide nanoparticles has also been shown to improve device response times. 16 Modification of the conjugated backbone structure of CPEs has been another strategy but has previously produced mixed results; incorporating benzothiadiazole units into otherwise fluorene backbones has succeeded in increasing PLED device performance in some cases, 15 while in others it has led to drastically reduced device performance, the reasons for which are poorly understood. 37,39 This work looks to explain how varying the π-conjugated structure of CPEs affects both PLED electroluminescence (EL) turn-on times and device performance (luminous and luminous power efficiency).…”

Effects of Graphene Oxide (GO) and Reduced Graphene Oxide (rGO) on Green-Emitting Conjugated Copolymer’s Optical and Laser Properties Using Simulation and Experimental Studies

“…CPs are often combined with other materials to tailor the properties in hybridizing or compositing processes. Organic-inorganic hybrid lightemitting diodes (HyLEDs) based on ZnO nanoparticle blends used as LED electron injection layers were designed by I. Hamilton et al [20].…”