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Abstract
Asymmetric-donor–acceptor (D2D2′–A) conjugates for simultaneously accessing blue room-temperature phosphorescence (BRTP) and blue thermally activated delayed fluorescence (BTADF).
Highlights
Single-component organic luminescent materials (SCOLMs) that show emission features with high photoluminescence quantum yield (PLQY) utilizing both singlet and triplet excited states have attracted increasing attention for their potential use in organic chemical sensing,[1,2] and bio-imaging[3] (Fig. 1)
Our studies revealed that both compounds (0.1% poly(methyl methacrylate), PMMA) under ambient conditions show both-BRTP (CPPN: phosphorescence quantum yield, FP = 3%; CPPNF: FP = 3.5%) and BTADF (CPPN: fluorescence quantum yield, FF = 43%; CPPNF: FF = 44%) due to the radiative decay of the upper triplet (TPPN) state and reverse intersystem crossing (rISC) from the lower-lying triplet (TCzPN) state to the singlet (SCzPN) state
To understand the number of excited states involved in the process, time resolved emission spectra (TRES) measurements were performed at 77 K. These studies show that the emission peaks of both compounds bathochromically shift from 455 to 475 nm (Fig. 6 and Fig. S11, Electronic supplementary information (ESI)†). When we compare these results with the TRES data recorded at RT, we found that the spectrum obtained at B2 ns is closely overlapped by the unrelaxed TRES data at RT (3.2 ns) (Fig. S11, ESI†)
Summary
Single-component organic luminescent materials (SCOLMs) that show emission features with high photoluminescence quantum yield (PLQY) utilizing both singlet and triplet excited states have attracted increasing attention for their potential use in organic chemical sensing,[1,2] and bio-imaging[3] (Fig. 1). The molecular vibrations that readily increase the non-radiative pathways of the localized triplet excitons become another major bottleneck to harvest efficient phosphorescence yield.[36] To circumvent the above issues, crystal formation,[37,38] aggregation,[39,40] host– guest interactions[41] and deuteration[42] have been studied to reduce the nonradiative pathways under ambient conditions To observe both blue-TADF (BTADF) and blue-RTP (BRTP) simultaneously with high PLQY from the SCOLMs under ambient conditions becomes a difficult task in the field of chemical physics. The photoluminescence studies of CPPNF in the hydrogen-bond (H-B) matrix further show that it exhibits PRTP with lifetimes of 39.51 ms and 269.21 ms
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