In order to overcome the low energy transfer efficiency of the conventional FRET (Forster resonance energy transfer) system, a novel spectra-matching and distance-controllable CIS@ZnS-SQ FRET assembly has been prepared via ultrasonic self-assembly method, by using the synthesized visible CIS@ZnS type I core-shell quantum dots as energy donor and the near infrared SQ dyes as acceptor. Through controllable synthesis of quantum dots, the absorption and fluorescence performance of FRET system were adjusted by the size of CIS@ZnS, while the distance of energy donor-acceptor and the non-valid charge recombination in the FRET system were controlled by the wide-band shell of quantum dots. The excitons transfer and recombination kinetics in CIS@ZnS-SQ assembly were investigated by the pump-probe femtosecond ultrafast transient absorption measurements, with which results in the FRET-type energy transfer mechanism: CIS*+SQ→CIS+SQ* has been proven and a high energy transfer rate of about 5.0×10 s has been gained between CIS@ZnS and SQ. The excitons’ lifetime and FRET energy transfer efficiency were calculated from the fluorescence decay kinetic curves tested by time-resolved fluorescence measurements. The results show that the energy transfer in CIS@ZnS-SQ depends on the size of CIS@ZnS quantum dots. As the size of CIS@ZnS (mainly refers to the ZnS shell thickness) increases from 2.1±0.4 nm to 2.9±0.4 nm, 4.1±0.3 nm, 5.4±0.5 nm and 7.2±0.5 nm, the fluorescence quantum yield of CIS@ZnS improves from 5.4% to 26%, 33%, 38% and 43.3% as well as the distance between CIS@ZnS and SQ (energy donor and acceptor) increases gradually, which makes the FRET energy transfer efficiency (ηFRET) first rise and then decline. As a result, an optimal ηFRET value of 62.8% was gained in the FRET assembly when the reaction time of ZnS shell was 20 min. This research will have a promising theoretical and practical value for the development of the panchromatic and high-efficiency solar cells.

中文翻译：

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基于I型核壳量子点的全色高效能量传输组件

为了克服传统 FRET（Forster 共振能量转移）系统能量转移效率低的问题，采用超声自组装方法制备了一种新型光谱匹配和距离可控的 CIS@ZnS-SQ FRET 组件。合成可见 CIS@ZnS I 型核壳量子点作为能量供体，近红外 SQ 染料作为受体。通过量子点的可控合成，FRET系统的吸收和荧光性能通过CIS@ZnS的大小来调节，而FRET系统中能量供体-受体的距离和无效电荷复合则由宽-量子点的带壳。通过泵浦探针飞秒超快瞬态吸收测量研究了 CIS@ZnS-SQ 组件中的激子转移和复合动力学，这导致了 FRET 型能量转移机制：CIS*+SQ→CIS+SQ* 已被证明，并且在 CIS@ZnS 和 SQ 之间获得了约 5.0×10 s 的高能量转移速率。激子的寿命和 FRET 能量转移效率是根据通过时间分辨荧光测量测试的荧光衰减动力学曲线计算的。结果表明，CIS@ZnS-SQ 中的能量转移取决于 CIS@ZnS 量子点的大小。随着 CIS@ZnS 的尺寸（主要是指 ZnS 壳厚度）从 2.1±0.4 nm 增加到 2.9±0.4 nm、4.1±0.3 nm、5.4±0.5 nm 和 7.2±0.5 nm，CIS@的荧光量子产率ZnS 从 5.4% 提高到 26%、33%、38% 和 43.3%，并且 CIS@ZnS 和 SQ（能量供体和受体）之间的距离逐渐增加，这使得 FRET 能量转移效率 (ηFRET) 先上升后下降。结果，当 ZnS 壳的反应时间为 20 分钟时，在 FRET 组件中获得了 62.8% 的最佳 ηFRET 值。该研究对开发全色高效太阳能电池具有广阔的理论和实用价值。