MIIT Key Laboratory of Critical Materials Technology for New Energy Conversion and Storage, School of Chemistry and Chemical Engineering & Key Laboratory of Micro-systems and Micro-structures, Ministry of Education, Harbin Institute of Technology, Harbin, Heilongjiang 150001, People's Republic of China.
Institute for Lasers, Photonics, and Biophotonics and Department of Chemistry, University at Buffalo, State University of New York, Buffalo, New York 14260, USA.
Nanoscale. 2017 Feb 2;9(5):1934-1941. doi: 10.1039/c6nr09713h.
Photon management enables the manipulation of the number of input photons by conversion of two or more light quanta into one (upconversion) or vice versa (quantum cutting). Simultaneous realization of both these processes in a single unit provides unique opportunities of efficient utilization of photons throughout a broad spectral range. Yet, concurrent realization of these two parallel optical processes in one single unit remains elusive, limiting its impact on many existing or possible future applications such as for panchromatic photovoltaics. Here, we describe an epitaxial active core/inert shell/active shell/inert shell fluoride nanostructure to implement upconversion and quantum cutting within spatially confined and isolated rare-earth-doped active domains. The core area transforms infrared photons through trivalent erbium (Er) ions into three- and two-photon upconverted visible and near infrared luminescence, while the second shell domain splits an excitation photon into two near infrared photons through cooperative quantum cutting from one trivalent terbium ion (Tb) to two trivalent ytterbium ions (Yb). The inert layer in between the active domains is able to effectively suppress the destructive interference between upconversion and quantum cutting, while the outermost inert shell is able to eliminate surface-related quenching. This design enables the colloidal core/multishell nanoparticles to have an upconversion quantum yield of ∼1.6%, and to have a luminescence yield of the quantum cutting process as high as ∼130%. This work constitutes a solid step for flexible photon management in a single nanostructure, and has an implication for photonic applications beyond photovoltaics.
光子管理可通过将两个或更多光量子转换为一个（上转换）或将其转换为另一个（量子切割）来控制输入光量子的数量。在单个单元中同时实现这两个过程提供了在宽光谱范围内有效利用光子的独特机会。然而，在单个单元中同时实现这两个平行的光学过程仍然难以实现，这限制了其在许多现有或未来可能的应用中的影响，例如全色光伏。在这里，我们描述了一种外延活性核/惰性壳/活性壳/惰性壳氟化物纳米结构，以在空间受限和孤立的稀土掺杂活性域内实现上转换和量子切割。核心区域通过三价铒（Er）离子将红外光子转换为三光子和两光子上转换的可见和近红外发光，而第二个壳域通过从一个三价铥离子（Tb）到两个三价镱离子（Yb）的协同量子切割将一个激发光子分裂为两个近红外光子。活性域之间的惰性层能够有效地抑制上转换和量子切割之间的破坏性干扰，而最外层的惰性壳能够消除表面相关的猝灭。该设计使胶体核/多壳纳米颗粒的上转换量子产率约为 1.6%，并且量子切割过程的发光产率高达约 130%。这项工作为单个纳米结构中的灵活光子管理迈出了坚实的一步，并对超越光伏的光子应用具有重要意义。
