Deep‐Red to Near‐Infrared Thermally Activated Delayed Fluorescence in Organic Solid Films and Electroluminescent Devices

Abstract

The design and synthesis of highly efficient deep red (DR) and near-infrared (NIR) organic emitting materials with characteristic of thermally activated delayed fluorescence (TADF) still remains a great challenge. A strategy was developed to construct TADF organic solid films with strong DR or NIR emission feature. The triphenylamine (TPA) and quinoxaline-6,7-dicarbonitrile (QCN) were employed as electron donor (D) and acceptor (A), respectively, to synthesize a TADF compound, TPA-QCN. The TPA-QCN molecule with orange-red emission in solution was employed as a dopant to prepare DR and NIR luminescent solid thin films. The high doped concentration and neat films exhibited efficient DR and NIR emissions, respectively. The highly efficient DR and NIR organic light-emitting devices (OLEDs) were fabricated by regulating TPA-QCN dopant concentration in the emitting layers.

Quinoxaline and Pyrido[x,y‐b]pyrazine‐Based Emitters: Tuning Normal Fluorescence to Thermally Activated Delayed Fluorescence and Emitting Color over the Entire Visible‐Light Range

“…For example, the 10 wt % Q‐DMAC device exhibited a maximum η ext of 9.8 % (vs. 12.9 % at 5 wt %), and the 10 wt % i PP‐PXZ device exhibited a maximum η ext of 9.6 % (vs. 12.3 % at 5 wt %). The spectral redshift, along with efficiency decrease with increasing doping concentration, has been frequently observed in TADF OLEDs mainly due to concentration quenching effects . Similar to the observation in 5 wt % TADF OLEDs, in 10 wt % devices, the PP‐DMAC device showed higher efficiencies and enhanced efficiency stability at high brightness region than that of the isomer i PP‐DMAC, and all of these PP‐ and i PP‐based TADF emitters exhibited higher efficiencies than that of the Q‐based Q‐DMAC.…”

“…The spectral redshift, along with efficiency decrease with increasing doping concentration, has been frequently observed in TADF OLEDs mainly due to concentration quenching effects. [40,41] Similart ot he observation in 5wt% TADF OLEDs,i n1 0wt% devices,t he PP-DMAC device showed highere fficiencies and enhanced efficiency stabilitya th igh brightness region than that of the isomer iPP-DMAC, and all of these PP-and iPP-based TADF emitterse xhibitedh igher efficienciest han that of the Q-based Q-DMAC.H owever, the efficiencies of the 10 wt %P P-PXZ device are exceptionally reduced, in comparison with its isomer iPP-PXZ,w hich is contrary to the case at a5 wt % doping level. This shouldb eb ecause PP-PXZ was partially decomposed upon rapid heatingf or ah igher doping concentration, as provedb yt he detection of impurity in the residue of PP-PXZ after device fabrication.…”

Electron‐Rich Twistacene‐Modified Arylboron Donor–Acceptor Systems: Synthesis, Photophysics, and Electroluminescence with Hot Exciton Response

“…At present, OLEDsb ased on metal-free thermallya ctivated delayed fluorescence (TADF) materials have received growingi nterest for their possibility to generate 100 %i nternal quantum efficiency by the up-conversionf rom the nonradiative triplet states to the radiatives inglets tates. [1][2][3][4][5][6][7][8][9][10][11][12][13][14] Moreover,t he performance of certain TADF materials could compare with those of the phosphorescent OLEDs,a long with low costs and abun-dant resources. As the core building block of the desired compounds is responsible for the optoelectronic properties and molecular stability,t he rational designa nd functionalization of the core building blocks are of great importance.…”

Exploration of High Efficiency AIE‐Active Deep/Near‐Infrared Red Emitters in OLEDs with High‐Radiance

“…The EL peaks of TNZPs were located at 678–686 nm (Figure S20, Supporting Information), and their CIE coordinates were located at (0.69, 0.30) or (0.69, 0.31), indicating their NIR emission behaviors in film have been well maintained in devices. All devices turned on at a low voltage of 2.9 eV, which was lower than common NIR‐OLED devices, implying the fabricated device structure had lower carrier injection barrier. Additionally, the TNZPs‐based devices possessed higher maximum red luminance of 1344–1938 cd m −2 , demonstrating efficient injection, transport and recombination of holes and electrons (Figure C).…”