Synthesis and Performance in OLEDs of Selenium-Containing Phosphorescent Emitters with Red Emission Color Deeper Than the Corresponding NTSC Standard

Abstract

The synthesis of new iridium­(III) complexes containing a 2-(benzo­[b]­selenophen-2-yl)­pyridine ligand is reported along with their photophysical, thermal, electrochemical and electroluminescent properties. These complexes are characterized by deep red phosphorescence with photoluminescence quantum yields exceeding 31% in the solid state. Solid layers of the complexes were characterized by ionization potentials of 5.17–5.27 eV and electron affinities of 2.87–2.95 eV. Their thermal and electrochemical stabilities were proved by cyclic voltammetry and thermogravimetric analysis. Deep red selenium-based iridium phosphorescent emitters were used in red electroluminescent devices which were characterized by a deep red color with Commission Internationale de l’Eclairage (CIE 1931) chromaticity coordinates (x, y) of (0.69, 0.31). This color is deeper than that defined by the red color standard (0.67, 0.33) of the National Television System Committee (NTSC) or CIE 1931 of (0.68, 0.32) of the widely known red phosphorescent emitter bis­(1-phenylisoquinoline)­(acetylacetonate)­iridium­(III) (Ir­(piq)2(acac)). Using newly developed deep red iridium complexes, white hybrid wet-processable light-emitting devices were fabricated, the electroluminescence of which was characterized by a white color with a color rendering index (CRI) reaching 85. White hybrid OLEDs were obtained by mixing blue fluorescence, green thermally activated delayed fluorescence, and red phosphorescence. They showed a maximum brightness exceeding 10000 cd/m2 and a high external quantum efficiency of 6.3% as for solution-processed white devices.

Crystal structures of 3-halo-2-organochalcogenylbenzo[b]chalcogenophenes

“…Chalcogenophenes derivatives are an attractive synthetic class of compounds with a wide range of relevant applications in medicinal chemistry (Keri et al, 2017;Mahmoud et al, 2017;Paegle et al, 2016), electrochemistry (Wei et al, 2017;Shahjad et al, 2017), agrochemistry (Zani et al, 2004) and as organic semiconductors (Yang et al, 2018;Ostroverkhova, 2016).extended benzo[b]chalcogenophenes derivatives have been widely studied as improved materials for optoelectronic devices such as organic photovoltaic cells (OPVs) (Ashraf et al, 2015;An et al, 2018;Chen et al, 2017), liquid-crystal displays (LCD) (Ghosh & Lehmann, 2017;Mei et al, 2013), organic light-emitting diodes (OLEDs) (Grimsdale et al, 2009;Zampetti et al, 2017;Arsenyan et al, 2019), and in organic field-effect transistors (OFETs) (Lee et al, 2019;Tisovsky ´et al, 2019). Benzo[b]chalcogenophenes derivatives also show relevant biological activities as anti-tumor (Arsenyan et al, 2011) and anti-inflammatory agents (Shah et al, 2018).…”

Benzo[b]selenophene/thieno[3,2-b]indole-Based N,S,Se-Heteroacenes for Hole-Transporting Layers

“…At the same time, selenophene-based semiconductors exhibit a number of advantageous properties as compared to their thiophene-containing counterparts: narrower optical band gap, lower oxidation and reduction potentials, and well-organized solid-state packing due to strong intermolecular Se–Se interactions, all of which overall allow enhancing the performance of organic electronics devices based on such heteroacenes. − Taking into account these data, the incorporation of selenium atoms into π-conjugated frameworks and fused compounds, intended for the use in organic electronics, is clearly a promising molecular design strategy, allowing us to improve efficiency of these functional materials. , Therefore, research efforts aiming at elaboration of new types of selenophene-containing semiconductors as well as at studying their properties are fully justified from the perspective of further optoelectronic applications. Thus, various types of heteroacenes, containing thienopyrrole, , selenophenopyrrole, , or selenophenothiophene fragments, , have previously been synthesized and used as organic electronic materials.…”

“…20−22 Taking into account these data, the incorporation of selenium atoms into π-conjugated frameworks and fused compounds, intended for the use in organic electronics, is clearly a promising molecular design strategy, allowing us to improve efficiency of these functional materials. 23,24 Therefore, research efforts aiming at elaboration of new types of selenophene-containing semiconductors as well as at studying their properties are fully justified from the perspective of further optoelectronic applications. Thus, various types of heteroacenes, containing thienopyrrole, 13,18 selenophenopyrrole, 25,26 or selenophenothiophene fragments, 27,28 have previously been synthesized and used as organic electronic materials.…”

Management of Exciton for Highly-Efficient Hybrid White Organic Light-Emitting Diodes with a Non-Doped Blue Emissive Layer

“…Generally speaking, WOLEDs can be classified in three ways: all-fluorescent, all-phosphorescent, and hybrid (mostly a combination of fluorescent and phosphorescent materials) [4,5]. Unlike the all-fluorescent and all-phosphorescent WOLEDs, which often suffer from low efficiency or short lifetime, the hybrid WOLED strategy has been regarded as a feasible method to obtain devices with high performance [6,7,8], as they can combine the advantages of long-lifetime blue fluorophores and high-efficiency red and green phosphors [9,10,11]. Hybrid WOLEDs can be divided into two types of device structures: the single-emissive layer (single-EML) structure and the multi-emissive layer (multi-EML) structure [4,12,13,14,15].…”