A bright near-infrared (NIR) fluorescent molecule was developed based on the donor–acceptor–donor (D–A–D) approach using an aza-BODIPY analog called pyrrolopyrrole aza-BODIPY (PPAB) as an electron-accepting chromophore. Directly introducing electron-donating triphenylamine (TPA) to develop a D–A–D structure caused redshifts of absorption and emission of PPAB into the NIR region with an enhanced fluorescence brightness of up to 5.2×104 m−1 cm−1, whereas inserting a phenylene linker between the TPA donor and the PPAB acceptor induced solvatochromic behavior in emission. Transient absorption spectra and theoretical calculations revealed the presence of a highly emissive hybridized locally excited and charge-transfer state in the former case and the contribution of the dark charge-separated state to the excited state in the latter case. The bright D–A–D PPAB as a novel emitter resulted in a NIR electroluminescence with a high external quantum efficiency of 3.7 % and a low amplified spontaneous emission threshold of ca. 80 μJ cm−2, indicating the high potential for NIR optoelectronic applications.
Bibliographical noteFunding Information:
This work was supported by Grants‐in‐Aid for Scientific Research (B) (JSPS KAKENHI Grant no. JP19H02703 and JP19H02790), Challenging Exploratory Research (JSPS KAKENHI Grant no. JP18K19081 and JP20K21227), Scientific Research on Innovative Areas, “π‐System Figuration: Control of Electron and Structural Dynamism for Innovative Functions (no. 2601)” (JSPS KAKENHI Grant no. JP15H01001 and JP17H05160), the Murata Science Foundation, and JSPS Fellows (JSPS KAKENHI Grand no. JP19J12257). Y.K. thanks the Kyushu University Leading Program for “Molecular System for Devices” from MEXT, Japan. The work at Yonsei University was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government (MSIT) (No. 2020R1A5A1019141).
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All Science Journal Classification (ASJC) codes
- Organic Chemistry