Highly efficient pure white polymer light-emitting devices based on poly(N-vinylcarbazole) doped with blue and red phosphorescent dyes

Abstract

Efficient white-polymer-light-emitting devices (WPLEDs) have been fabricated with a single emitting layer containing a hole-transporting host polymer, poly(N-vinylcarbzole), and an electron-transporting auxiliary, 1,3-bis[(4-tert-butylphenyl)-1,3,4-oxadiazolyl]-phenylene, codoped with two phosphorescent dyes: Iridium(III)bis (2-(4,6-difluorophenyl)-pyridinato-N,C2') picolinate (FIrpic) and home-made Ir-G2 for blue and red emission, respectively. With the structure of ITO/ PEDOT:PSS 4083(40 nm)/emission layer(80 nm)/Ba(4 nm)/Al(120 nm), the device showed a maximal luminous efficiency (LE) of 13.5 cd A 1 (corresponding to an external quantum efficiency (EQE) of 6.8%), and a peak power efficiency (PE) of 6.5 lm W 1 at 6.0 V. Meanwhile, the device exhibited pure white emission with Commission Internationale de l'Eclairage (CIE) coordinates of (0.34, 0.35) at a current density of 12 mA cm 2 , which is very close to the equi-energy white point with CIE coordinates of (0.33, 0.33). The device performance can be further optimized when more balanced hole/electron injection is achieved by incorporating a lower conducting type anode buffer layer (PEDOT:PSS) and incorporating poly [(9,Ndimethylamino)propyl)-2,7-fluorenene)-alt-2,7-(9,9-dioctyfluorene)] (PFN) as an electron injection layer at the cathode. The optimized device showed an LE of 24.6 cd A 1 (with an EQE of 14.1%), while the peak power efficiency reached 12.66 lm W 1 . Moreover, the WPLEDs showed good electroluminescence (EL) stability over a wide range of operating current density and luminance.white polymer light-emitting device, phosphorescent iridium complex, anode buffer layer, water-/alcohol-soluble conjugated polymer

White Polymer Light‐Emitting Devices for Solid‐State Lighting: Materials, Devices, and Recent Progress

“…It has been realized that water/alcohol‐soluble PFN and its derivatives can be used as an efficient cathode buffer layer to improve the performance of WPLEDs . The optimization of WPLEDs with PFN interlayer by incorporating a low conducting PEDOT:PSS achieved a more balanced hole/electron transport in the active layer, leading to distinctly improved device performance . Gong et al reported efficient multi‐layered WPLEDs in which an emissive layer consists of a luminescent polyfluorene host of PFO‐ETM (PFO end‐capped with 5‐biphenyl‐1,3,4‐oxadiazole), poly[(9,9‐dioctyl‐2,7‐fluorene)‐ co ‐(2,2‐fluoren‐9‐one)] (PFO‐F, containing 1 mol% of 2,2‐fluoren‐9‐one) and an iridium complex of tris(2,5‐bis‐2’‐(9’,9’‐dihexylfluorene)pyridine)iridium(III) (Ir(HFP) 3 ), which was sandwiched between a water‐soluble PVK derivative (PVK‐SO 3 Li) as a hole‐injection/hole‐transport layer (HIL/HTL) and a water‐soluble PBD derivative of 4‐(5‐(4‐ tert ‐butylphenyl)‐1,3,4‐oxadiazole‐2‐yl)biphenyl‐4’‐yl sulfonic acid ( t ‐Bu‐PBD‐SO 3 H) as an electron‐injection/electron‐transport layer (EIL/ETL) .…”

Room temperature phosphorescence from natural products: Crystallization matters

“…The essential differences between fluorescence and phosphorescence are the degeneracy of the excited states, the far longer lifetimes of triplets versus singlets, and the sensitivities of triplets to a wider variety of quenching conditions. Such differences endow phosphorescent materials unique photophysical properties and advantages in a number of potential applications, for examples, organic light emitting diodes [1,2], photovoltaic devices [3,4], sensors [5,6] and bioimaging [7,8]. However, so far phosphorescent luminogens are essentially inorganic and organometallic compounds because metals could promote spin-orbit coupling.…”

Functional Dyes in Polymeric 3D Printing: Applications and Perspectives

“…At last, dyes are typically organic or organometallic molecules that can be inserted in a polymer either by dispersion or by covalent linkage to the chains through appropriate functional groups. The introduction of dyes in polymers allows obtaining light-emitting devices, electroluminescent polymers, temperature sensors, mechanochromic materials, or liquid crystals dispersed in polymers. − …”