钙钛矿CH3NH3PbI3与PbS量子点间的电荷转移动力学研究

Solar cells based on perovskite materials have attracted great attention due to their higher power conversion efficiencies (PCEs, up to 19.3%). However, the absorption onset of perovskite CH3NH3PbI3 is limited to 1.57 eV. Therefore, an effective approach to further increase the spectral response of these materials is co-sensitization with near IR absorbing nanoparticles. At present, near IR quantum dots (QDs)-perovskite co-sensitization solar cells are one of the most intensively investigated systems. At the heart of above work is how to improve their PCEs, but the dynamics mechanism of how the QDs plays a role in perovskite solar cells has never been reported. Our research, taking the PbS QDs and perovskite CH3NH3PbI3 as an example system, will realize a systematic research on the charge transfer dynamics and its dynamic mechanism between PbS QDs and CH3NH3PbI3 by spatial-resolved fluorescence imaging and time-resolved transient absorption. This will build the relationships between the microstructure- or size-charge transfer dynamics and seek to determine how variations between different nanoparticles, different sites and surface characters affect charge transfer. Our research will provide significant insights for the development of highly efficient CH3NH3PbI3-QDs co-sensitization solar cells.

钙钛矿太阳能电池因其较高的能量转换效率（PCEs，最高达19.3%）而引起了极大的关注，但一直存在着钙钛矿CH3NH3PbI3吸收带仅局限于1.57 eV的问题。因此，与吸收近红外光的纳米颗粒共敏化，是进一步提高钙钛矿材料光谱响应的有效方法之一。目前，对近红外量子点（QDs）-钙钛矿共敏化太阳能电池的研究较为广泛，但其研究的核心问题都是如何提高电池的PCEs，而QDs是如何在钙钛矿太阳能电池中发挥作用的动力学机理则从未涉及。本项目将以PbS QDs和钙钛矿CH3NH3PbI3分子为研究对象，利用空间分辨的荧光成像和时间分辨的瞬态吸收系统，实现对PbS QDs和CH3NH3PbI3间电荷转移动力学及其动力学机理的系统研究，建立材料微观结构、物理尺寸与电荷转移速率的相互关联，探索分子间的电荷转移作用机理，为建立高效的CH3NH3PbI3-QDs共敏太阳能电池体系提供材料表征和动力学基础。

钙钛矿（MPbX3，M是有机或无机阳离子，X是卤素离子）太阳能电池因其较高的能量转换效率（PCEs，最高达22.3%）而引起了极大的关注，同时不同形貌的钙钛矿材料自身的光电性能也存在明显差异。目前研究的重心大多集中在钙钛矿材料的设计、组装和改进，以进一步提高钙钛矿材料相关的器件性能。而影响钙钛矿载流子动力学的物理机理研究较少，尤其是钙钛矿中三体（Trion）激子动力学的研究，以及钙钛矿不同形貌完全可逆转换的实现均未涉及。本项目针对钙钛矿材料（CsPbBr3 QDs）三体激子动力学、不同形貌转化以及掺杂手段验证QDs类型进行了研究，主要取得了如下一些成果：1）发展了一种对钙钛矿进行无损掺杂的全新方法，并利用该方法测到了钙钛矿CsPbBr3 QDs的三体激子寿命；2）通过阳离子交换反应，深入系统研究了3D和2D钙钛矿薄膜的完全可逆转化及其电荷的定向分离动力学；3）采用光化学掺杂手段对不同类型半导体QDs进行电子掺杂，并通过该方法精确辨别了（CdSe/CdS DIRs）的类型（类型I和准-类型II）。