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Different RISC rates in benzoylpyridine-based TADF compounds and their implications for solution-processed OLEDs
Dyes and Pigments ( IF 4.5 ) Pub Date : 2020-06-18 , DOI: 10.1016/j.dyepig.2020.108579
Domantas Berenis , Gediminas Kreiza , Saulius Juršėnas , Egidijus Kamarauskas , Virginijus Ruibys , Olegas Bobrovas , Povilas Adomėnas , Karolis Kazlauskas

Reverse intersystem crossing (RISC) rate is among the key parameters of TADF compounds affecting triplet upconversion and annihilation processes, and thus determining efficiency roll-off in TADF-OLEDs. Herein, control of RISC rate (kRISC) in a series of benzoylpyridine-based TADF compounds via carbazole donor linking positions is demonstrated. Regardless of the similar singlet-triplet energy splitting found in the compounds with meta- or para-carbazole linking topologies, meta-Cz compounds exhibited stronger singlet-triplet state coupling resulting in 10-fold larger kRISC (up to ~2 × 106 s−1) as that in para-Cz counterparts. Different kRISC was shown to have important implications for the solution-processed TADF-OLEDs based on the benzoylpyridines. Explicitly, in the non-doped devices based on neat meta-Cz emissive layers, larger kRISC was crucial for the reduced roll-off. Conversely, in 1.2 wt% rubrene-doped hyperfluorescent devices employing benzoylpyridines as TADF hosts, insignificant roll-off was observed irrespective of kRISC, provided it is above 105 s−1. The obtained results give insight into the possibilities of controlling kRISC in benzoylpyridines and demonstrate its importance for efficiency roll-off of TADF and hyperfluorescent OLEDs.



中文翻译:

基于苯甲酰基吡啶的TADF化合物的不同RISC速率及其对溶液加工OLED的影响

逆系统间穿越(RISC)速率是影响三重态上转换和an灭过程的TADF化合物的关键参数之一,因此决定了TADF-OLED中的效率下降。在本文中,证明了通过咔唑供体的连接位置来控制一系列基于苯甲酰基吡啶的TADF化合物中的RISC速率(k RISC)。不管在具有间-对-咔唑连接拓扑的化合物中发现类似的单重态-三重态能量分裂,-Cz化合物均表现出更强的单重态-三重态状态耦合,从而导致k RISC增大10倍(高达〜2×10 6) š -1),其在对位Cz同行。结果表明,不同的k RISC对基于苯甲酰基吡啶的溶液处理TADF-OLED具有重要意义。明确地,在基于纯meta- Cz发射层的非掺杂器件中,较大的k RISC对于降低滚降至关重要。相反,在使用苯甲酰吡啶作为TADF主体的1.2 wt%的红宝石掺杂的超荧光器件中,如果k RISC大于10 5 s -1,则观察到不明显的滚降。获得的结果使人们深入了解了控制k RISC的可能性 在苯甲酰吡啶中的应用,并证明了其对TADF和超荧光OLED效率下降的重要性。

更新日期:2020-06-23
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