Computational design of low singlet-triplet gap all-organic molecules for OLED application

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• 作者：Begoñ ; a Miliá ; n-Medina ; Johannes Gierschner ; ^{johannes.gierschner@imdea.org}
• 关键词：Organic light emitting diodes ; Organic solar cells ; Material design ; Optical properties ; External quantum efficiency ; Singlet&ndash ; triplet gaps
• 刊名：Organic Electronics
• 出版年：2012
• 期刊代码：137_15661199
• 类别：et
• 出版时间：June, 2012
• 卷：13
• 期：6
• 页码：985-991
• 文件大小：598 K

摘要

It was recently reported that external quantum efficiency in organic LEDs can be substantially enhanced when triplet excitons are harvested through upconversion by m>Em>-type delayed fluorescence in materials with small singlet-triplet energy gap 螖m>Em>_ST, based on donor-acceptor (DA) chromophores. Furthermore, organic solar cells (OSCs) might profit from such materials in order to reduce recombination losses. However, targeted design rules for such materials are missing up to now. In this paper, we follow a facile (TD-)DFT-based computational design concept by engineering the fragment frontier orbitals in DA systems. The calculations show that optimized systems with very small 螖m>Em>_ST in the range of kT can be achieved by balancing the energetic offset between fragment MOs as well as through the nature of the DA connector. Application in OLED will additionally require small non-radiative rates, which recommends large bandgap materials. Utilization in polymeric DA systems with small 螖m>Em>_ST in OSCs requires the full exploration of the chain length dependence of the respective oligomers.