Bright and efficient inverted organic light-emitting diodes with improved solution-processed electron-transport interlayers

Realizing 8 cd A−1 Current Efficiency for Solution-Processed Inverted Top-Emitting Polymer Light-Emitting Diodes

“…Solution-processed EIL for QLEDs and for top-illuminated solar cells are reported in the literature: zinc oxide (ZnO) nanoparticles for topilluminated solar cells 35 and ZnO nanocrystal for TQLED. 37 It has been shown that inverted BOLEDs using only ZnO as EIL are less efficient, as the ZnO work function is too high to efficiently inject the electrons into the emitter's lowest unoccupied molecular orbital (LUMO) 38,39 Hou et al published an inverted TOLED structure in 2005, using a reflective aluminum cathode and aminoalkyl-substituted conjugated quanternized polyfluorene copolymers mixed with 0.5% mol benzothiadiazole as EIL and deposited by solution process. 31 The TOLED based on poly(2-methoxy,5-(2-ethylhexyloxy)-1,4-phenylenevinylene) (MEH-PPV) polymeric emitter reached 1.6 cd A À1 at an operating voltage of 13.3 V, showing a low electron injection.…”

“…31 The TOLED based on poly(2-methoxy,5-(2-ethylhexyloxy)-1,4-phenylenevinylene) (MEH-PPV) polymeric emitter reached 1.6 cd A À1 at an operating voltage of 13.3 V, showing a low electron injection. Over the past few years, research efforts have been focusing on the development of solution-processable electron injection materials for inverted BOLED devices, and particular attention has been given to polyethylenimine ethoxylated (PEIE) [39][40][41] and polyethylenenimine (PEI) 38,[41][42][43] since 2012. These two polymers, once deposited on top of an electrode, reduce its work function by 1 eV, leading to high electron injection.…”

“…41 They are coupled with a ZnO layer to avoid exciton quenching at the interface cathode/ EIL. 38 This work aims to build solution-processed inverted TOLEDs which are as efficient as the BOLEDs we optimized in a previous work 39 and based on the poly(para-phenylene vinylene) (PPV) derivative copolymer Super Yellow. A MoO x /Ag/ MoO x (MAM) stack is used as the top electrode with a 15 nm thick Ag layer and a 10 nm thick MoO x layer used as HIL.…”

All solution-processed ITO free flexible organic light-emitting diodes

“…We show in a previous work that the use of a hole blocking layer is required. 55 A small molecule 1,3,5-tris(N-phenylbenzimidazol-2-yl) (TPBi) is used and directly mixed in the PEIE ink. 55 This process avoids the deposition of an ultra-thin PEIE layer, which is difficult to up-scale in the R2R process.…”

Efficient Solution‐Processed Inverted Organic Light‐Emitting Diodes by Using Polyethyleneimine as Interface Layer

“…However, it requires a complex fabrication process, which can limit the size of displays and make them expensive . Therefore, solution‐processed devices are more desirable because of its low cost, high throughput and suitability for large area and flexible substrates . Nevertheless, the problems of interface mixing between neighboring layers are inevitable, which will cause low efficiency and short lifetimes, so the fabrication of devices with multilayered functional layers following the solution processing technique remains very challenging .…”