Modulation of red organic room-temperature phosphorescence in heavy atom-free phosphors. (September 2021)

• Record Type: Journal Article
• Authors: Liao, Fan; Du, Jiajun; Nie, Xiancheng; Wu, Ziye; Su, Hao; Huang, Wenhuan; Wang, Tao; Chen, Biao; Jiang, Jun; Zhang, Xuepeng; Zhang, Guoqing
• Is Part Of: Dyes and pigments. Volume 193(2021)
• Publication Date: 2021-09
• Subjects: Room-temperature phosphorescence -- Charge transfer -- Triplet state -- Red/near infrared -- Naphthalene diimide; Dyes and dyeing -- Periodicals; Pigments -- Periodicals; 667.2
• DOI: 10.1016/j.dyepig.2021.109505
• Languages: English
• ISSNs: 0143-7208

Abstract

Abstract: Red room temperature phosphorescence (RTP) was conventionally obtained by incorporating heavy metal ions or halogens. However, heavy metals are toxic and expensive while C-halogen bonds are usually prone to photobleaching. Meanwhile, heavy atoms often lead to much reduced RTP lifetimes, precluding their use in certain fields. Herein, a series of naphthalene diimides with various electron-donor substituents on the nitrogen atoms were used to achieve red RTP. It was found that a moderate intramolecular charge transfer (CT) state provides mediating intersystem crossing channels for promoting red RTP with quantum yields circa. 5%. However, much stronger donors can in fact inhibit all forms of luminescence emission including RTP via photo-induced electron transfer quenching at room temperature, in which case the red phosphorescence could be restored if the donor, such as an amine, is suppressed by protonation.