High-Efficiency Red and Near-Infrared Organic Light-Emitting Diodes Enabled by Pure Organic Fluorescent Emitters and an Exciplex-Forming Cohost

Abstract

Three D-A-D-configured molecules DTPBT, DTPNT, and DTPNBT with high quantum yield of orange red (628 nm), red (659 nm), and deep-red/NIR (710 nm) fluorescence, respectively, were developed as emitting dopants in an exciplex-forming cohost (TCTA:3P-T2T) for high-efficiency fluorescence-based organic light-emitting diodes (OLEDs). The obtained physical properties together with theoretical calculations analyzed from these new molecules establish a clear structure–property relationship, in which the feature of central acceptor 2,1,3-benzothiadiazole (BT), naphtho­[1,2-c:5,6-c′]­bis­[1,2,5]­thiadiazole (NT), and 2,1,3-naphthothiadiazole (NBT) plays the crucial role for governing the physical characteristics. The optimized device configured as ITO/HAT-CN/TAPC/TCTA/TCTA:3P-T2T:5% emitter/3P-T2T/LiF/Al gave a record-high efficiency of orange red (591 nm, 15%), red (647 nm, 10%), and deep-red/NIR (689 nm, 9%) electroluminescent devices. The effective harvest of triplet excitons with an exciplex-forming system in conjunction with efficient energy transfer between the exciplex and the dopant is beneficial for such high device efficiencies. More importantly, the stable exciplex-forming cohost and fast radiative decay rate of DTPNT render this particular device exhibiting high device stability as indicated by the low efficiency roll-off under high current densities (EQE (external quantum efficiency) values of 8.1% at 1000 cd m–2 and 6.8% at 10,000 cd m–2). These results reveal the potential of employing an exciplex-forming system as cohost for fluorescent dopants to furnish high-efficiency OLEDs with an emission wavelength extending to the red or even the NIR range.

White Organic Light-Emitting Diodes from Single Emissive Layers: Combining Exciplex Emission with Electromer Emission

“…Recently, exciplex − and electroplex − -based OLEDs have gained a lot of attention due to their thermally activated delayed fluorescence (TADF) properties. − Exciplexes and electroplexes are excited-state complexes formed by oppositely charged adjacent molecules with weak coulombic interactions. Exciplex excitons can be generated under optical excitation, whereas electroplexes require an electric field.…”

Nanostructured Organic/Hybrid Materials and Components in Miniaturized Optical and Chemical Sensors

“…To date, the OLEDs technology is already at an industrial stage thanks to the huge progress in OLED-based displays. The use of organometallic complexes based on noble metals such as platinum, iridium and osmium has guaranteed a wide color tunability (covering the whole visible and NIR range) and a high stability in operating conditions [52,53]. Red and green OLEDs easily reach lifetimes up to 10 6 h, while only recently blue OLEDs have shown improved device lifetimes up to 10 3 h [54].…”

P‐130: A Full Screen Biometric Identification Approach for OLED Displays by Using Near‐Infrared OLED

“…Near-infrared (NIR) has also been applied in the medical field (e.g. in optical coherence tomography), information processing and night-vision [18] [20]. In this work, we propose to integrate a NIR OLED into the display as a light source for biometric identification, as shown in Fig.…”