Energy harvesting of non-emissive triplet excitons in tetracene by emissive PbS nanocrystals
Energy harvesting of non-emissive triplet excitons in tetracene by emissive PbS nanocrystals
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DOI：
10.1038/nmat4097
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发表时间：
2014-11-01
期刊：
影响因子：
41.2
通讯作者：
Baldo, Marc A.
中科院分区：
文献类型：
--
作者：
Thompson, Nicholas J.;Wilson, Mark W. B.;Baldo, Marc A.
三重态激子在有机光电子学中普遍存在，但它们通常是不期望的能量汇，因为它们被自旋禁止发光，并且它们的高结合能阻碍自由电子-空穴对的产生。因此，收集它们的能量是一项重要的技术挑战。在这里，我们证明了直接激子能量转移从“黑暗”的三重态在有机半导体并四苯胶体硫化铅纳米晶体，从而成功地利用分子三重态激子在近红外。瞬态光致发光研究支持的稳态激发光谱表明，转移效率至少为（90 +/- 13）%。其机制是一个Dexter跳跃过程，包括两个电子的同时交换。三重态激子向纳米晶体的转移有望广泛应用于太阳能和近红外发光应用，而目前缺乏有效的分子荧光粉。特别地，这种“增亮”低能分子三重态激子的途径可以允许常规硅太阳能电池的单重态激子裂变敏化。
Triplet excitons are ubiquitous in organic optoelectronics, but they are often an undesirable energy sink because they are spin-forbidden from emitting light and their high binding energy hinders the generation of free electron-hole pairs. Harvesting their energy is consequently an important technological challenge. Here, we demonstrate direct excitonic energy transfer from 'dark' triplets in the organic semiconductor tetracene to colloidal PbS nanocrystals, thereby successfully harnessing molecular triplet excitons in the near infrared. Steady-state excitation spectra, supported by transient photoluminescence studies, demonstrate that the transfer efficiency is at least (90 +/- 13)%. The mechanism is a Dexter hopping process consisting of the simultaneous exchange of two electrons. Triplet exciton transfer to nanocrystals is expected to be broadly applicable in solar and near-infrared light-emitting applications, where effective molecular phosphors are lacking at present. In particular, this route to 'brighten' low-energy molecular triplet excitons may permit singlet exciton fission sensitization of conventional silicon solar cells.