Efficient near-infrared emission benefits from slowing down the internal conversion process

• Published in: Chemical science (Cambridge) Vol. 15; no. 15; pp. 5589 - 5595
• Main Authors: Xie, Mingliang, Zhou, Yannan, Zhou, Huayi, Ma, Chengling, Sun, Qikun, Zhang, Shi-Tong, Zhang, Yujian, Yang, Wenjun, Xue, Shanfeng
• Format: Journal Article
• Language: English
• Published: CAMBRIDGE Royal Soc Chemistry 17.04.2024; Royal Society of Chemistry; The Royal Society of Chemistry
• Subjects: Charge materials; Charge transfer; Chemistry; Chemistry, Multidisciplinary; Emitters; Excitons; Internal conversion; Near infrared radiation; Photoluminescence; Physical Sciences; Quantum efficiency; Rigid structures; Science & Technology; LIGHT-EMITTING-DIODES
• DOI: 10.1039/d4sc00841c
• ISSN: 2041-6520

Organic deep-red (DR) and near-infrared (NIR) emitters with high photoluminescence quantum yield (PLQY) are rare due to the strong non-radiative ( k nr ) decay. Here, we report two DR/NIR emitters with high PLQY, TPANZPyPI and TPANZ3PI . Interestingly, the TPANZPyPI film exhibits 46.5% PLQY at 699 nm. Theoretical calculations indicate that TPANZPyPI can achieve this high PLQY in the near-infrared emission region due to its small S 1 to S 0 internal conversion (IC) rate. Meanwhile, research has found that, compared to TPANZ3PI , TPANZPyPI with a more rigid structure can effectively suppress the T 2 to T 1 IC process, which is conducive to higher exciton utilization efficiency (EUE). TPANZPyPI 's non-doped OLED shows NIR emission with 4.6% @ 684 nm maximum external quantum efficiency (EQE max ). Its doped OLEDs radiate DR with an EQE max of 6.9% @ 666 nm. These EQEs are among the highest values for hybridized local charge transfer state materials emitting more than 640 nm. This work demonstrates for the first time, based on a combination of theory and experiment, that increasing the molecular rigidity can inhibit the excited state IC process in addition to the S 1 to S 0 IC, realizing efficient electroluminescence. This work demonstrates for the first time that emitters with appropriate qualifications can affect the IC from S 1 to S 0 and the IC of the triple excluded state, achieving high-efficiency device performance.