Unveiling the Aging Process of Organic Light‐Emitting Devices with Langevin and Hole Trap‐Assisted Recombination Exciplex Cohosts

Abstract

Exciplex-forming cohosts have gained increasing interest due to their promising performances in organic light-emitting diodes (OLEDs). Such electroluminescent stabilities of the exciplex cohosts depend on their chargecarrier recombination. But intrinsic relationships between the recombination schemes and the electrical aging process of the exciplex cohosts are yet to be revealed. In this case, exciplex cohosts with two different recombination schemes, namely trap-assisted recombination (TAR) and trimolecular Langevin recombination (LR), are compared. The LR-dominated device achieves T 90 lifetime (time to 90% of initial luminance) of ≈8600 h at luminance of 1000 cd m −2 , which is >2.3-time lifetime improvement compared with the hole TAR-dominated ones. The corresponding degradation analyses confirms that hole carriers in hole TAR-dominated cohosts are captured by phosphorescent guests, accelerating p-type cohost deterioration through exciton-polaron decomposition on susceptible aromatic amine groups, which reveals the electrical aging mechanism of exciplex cohost based devices. Moreover, exciton managements of the recombination region further suppress luminous decline and release undesirable exciton-exciton annihilations. The current findings offer an in situ technique to observe exciton and charge carrier aging processes with different recombination mechanisms and provide a general guidance for the development of highly efficient and longlifespan exciplex cohost based OLEDs.

Realizing Stable Narrowband Emission Blue Fluorescent Organic Light-Emitting Diodes with Dual-Channel Triplet Exciton Harvesting Host

“…To reveal the origin of the significantly improved device stability and explore the difference in exciton dynamics before and after aging of the devices based on PAC and MADN, their transient EL decay curves are recorded. Both PAC- and MADN-based devices show less delayed fluorescence component after aging, which can be attributed to the formation of exciton annihilation centers and charge trapping centers due to the defects generated after the aging process . Although the exciton lifetime of the PAC-based device is longer than that of the MADN-based device, the PAC-based device has a smaller fraction of long-lived excitons.…”

“…Both PAC-and MADN-based devices show less delayed fluorescence component after aging, which can be attributed to the formation of exciton annihilation centers and charge trapping centers due to the defects generated after the aging process. 31 Although the exciton lifetime of the PAC-based device is longer than that of the MADN-based device, the PAC-based device has a smaller fraction of long-lived excitons. To compare the specific change of exciton lifetime before and after aging more clearly, the change of transient EL decay curve area can be integrated, and the relative exciton quenching center formation rate can be calculated according to Figure 5.…”

Toward Narrowband and Efficient Blue Fluophosphors by Locking the Stretching Vibration of Indolocarbazole Skeletons

“…The presented materials of HATCN, BH, BPBPA, and BCzPh were purchased from Luminescence Technology Co., Ltd. DPPyA and pDBF-Ph-TRZ were prepared according to the reported methods, , while Liq was purchased from Jilin OLED Material Tech Co., Ltd.…”

Polaronic Stabilities of Exciton Sensitizers Govern Operational Lifetime of Thermally Activated Delayed Fluorescence Assisted Fluorescence Organic Light‐Emitting Devices

“…[6][7][8][9][10] Pioneering studies on phosphorescent and TADF OLEDs elucidated the intrinsic degradation pathways and their key intermediates as polarons, [11,24] excitons, [12,[25][26][27][28][29][30][31][32][33][34][35][36][37][38][39][40][41][42] and their derivatives. [43][44][45][46][47][48][49][50][51][52][53][54][55][56][57] This mechanistic understanding offered valuable insights for enhancing the operational longevity of OLEDs. [20,52, Recently, research has focused on exploring strategies to improve the longevity of TAF-OLEDs.…”

“…[ 6–10 ] Pioneering studies on phosphorescent and TADF OLEDs elucidated the intrinsic degradation pathways and their key intermediates as polarons, [ 11,24 ] excitons, [ 12,25–42 ] and their derivatives. [ 43–57 ] This mechanistic understanding offered valuable insights for enhancing the operational longevity of OLEDs. [ 20,52,58–78 ]…”