3 years ago

Tilted Spiro-Type Thermally Activated Delayed Fluorescence Host for ≈100% Exciton Harvesting in Red Phosphorescent Electronics with Ultralow Doping Ratio

Tilted Spiro-Type Thermally Activated Delayed Fluorescence Host for ≈100% Exciton Harvesting in Red Phosphorescent Electronics with Ultralow Doping Ratio
Ya-Kun Wang, Zuo-Quan Jiang, Sheng-Fan Wu, Si-Hua Li, Man-Keung Fung, Liang-Sheng Liao, Sarvendra Kumar, Chen-Chao Huang
Despite promising efficiency, the high fabrication cost due to the required high concentrations of noble metal based phosphors is still problematic for phosphorescent organic light-emitting diodes (PhOLEDs). This situation becomes even serious considering some practical applications need high luminance, which in turn requires a higher concentration of emitters. A paradigm shift to circumvent these issues can be development of materials that are able to operate efficiently in very low concentrations (<1 wt%). Here, two thermally activated delayed fluorescence hosts (OSTFPCN and OSTFPB) with tilted spiro geometry, small singlet-triplet splitting (Δ E st), and effective resonance energy transfer are developed. Within expectation, record performances with a power efficiency of 63.6 lm W−1 and an external quantum efficiency (EQE) of 31.2% for the red phosphor Ir(MDQ)2(acac) (2.0 wt%) are achieved with OSTFPCN as host. Additionally, a high power efficiency around 58 lm W−1 is also gained even at an ultralow dopant concentration of 0.5 wt% for a OSTFPB based device. Mechanism studies demonstrate that efficiency roll-off can be effectively suppressed in such low concentrations. These findings pave a new way to exploit low cost and high efficiency PhOLEDs. Two tilted spiro geometry based thermally activated delayed fluorescence type hosts are developed and implemented as host for organic light-emitting diodes. Record power efficiency of 63.6 lm W−1 and external quantum efficiency (EQE) of 31.2% for Ir(MDQ)2(acac) based device are obtained. Notably, even under ultralow phosphor dopant concentration (0.5 wt%), high power efficiency of around 58 lm W−1 is still achievable.

Publisher URL: http://onlinelibrary.wiley.com/resolve/doi

DOI: 10.1002/adfm.201706228

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