Stable luminescent π-radicals with doublet emission have aroused a growing interest for functional molecular materials. We have demonstrated a neutral π-radical dye (4-N-carbazolyl-2,6-dichlorophenyl)bis(2,4,6-trichlorophenyl)-methyl (TTM-1Cz) with remarkable doublet emission, which could be used as triplet sensitizer to initiate the photophysical process of triplet–triplet annihilation photon upconversion (TTA-UC). Dexter-like excited doublet-triplet energy transfer (DTET) was confirmed by theoretical calculation. With the same sensitizer, a mixed solution of TTM-1Cz and aromatic emitters could upconvert red light (λ = 635 nm) to blue or cyan light. An anti-Stokes energy shift as large as 0.92 eV was observed from red to blue light upconversion. This finding of DTET phenomena offers a new kind of triplet sensitizer for TTA-UC.

中文翻译：

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Doublet–Triplet能量转移主导的光子上转换

具有双重发射的稳定的发光π自由基引起了人们对功能分子材料的日益增长的兴趣。我们已经证明了一种中性的π自由基染料（4- N-carbazolyl-2,6-dichlorophenyl）bis（2,4,6-trichlorophenyl）-methyl（TTM-1Cz）具有显着的双峰发射，可以用作三重峰敏化剂，以引发三重峰-三重态an灭光子的光物理过程（TTA-UC）。理论计算证实了Dexter样的激发双峰三重态能量转移（DTET）。使用相同的敏化剂，TTM-1Cz和芳香族发射体的混合溶液可以将红光（λ= 635 nm）上转换为蓝光或青色光。从红光到蓝光的上转换观察到高达0.92 eV的反斯托克斯能量偏移。DTET现象的发现为TTA-UC提供了一种新型的三重态敏化剂。