多重激子效应钙钛矿结构CsSnI量子点的设计与性能调控

Quantum dots with multiple excitons generation (MEG) can generate multiple charge pairs under excitation of the single photon, which will break through the theoretical limitation of photovoltaic-conversion of traditional semiconductors. So quantum dots possesses a great potential application prospect in the field of photoelectric materials. But previous works showed that quantum dots produced MEG only when incident optical wavelength was less than 400 nm. Quantum dots could not produce MEG when incident optical wavelength was above 400 nm. Therefore, the performance of quantum dot devices is much lower than that of theoretical value. Our works revealed that the quantum dots with graded distribution of energy band gap (Eg) would produce MEG in wide wavelength region (~800 nm) through multiband photon coupling. However, the traditional binary quantum dots cannot get highly efficient MEG by adjusting their structure. Here, we propose an idea of multicomponent perovskite structured CsSnI quantum dot to solve the questions above. Rb and Br will be introduced in the perovskite structure to replace Cs and I, respectively, due to similar tolerance factor, which increases the electronic excitation of quantum dots. The graded Eg and multistage MEG threshold energy will be formed by adjusting atomic ratio, thereby effectively utilizing the multiband photon coupling to produce highly efficient MEG in wide wavelength region. In order to realize the idea, we will focus on the research: controlled microwave synthesis and mechanism of quantum dots; the relationship among atomic ratio, energy band structure and MEG threshold energy; dynamics of constraint and transition of photo-generation excitons.

具有多重激子效应(MEG)的量子点在单一光子激发下产生多个电荷对，可以突破半导体光电转换的理论极限，展现出巨大的应用潜力。但研究显示，量子点只有入射光波长<400nm才产生MEG，波长>400nm则无法实现MEG，这是其器件性能远低于理论值的重要原因。我们的研究表明，能带宽度(Eg)呈梯度分布的量子点可以利用多波段光子耦合作用，在宽波(~800nm)区形成MEG。但传统二元量子点难以通过调控结构获得高效MEG，为此，本项目提出多组元钙钛矿结构CsSnI量子点的思想来解决这一问题：引入容差因子相近的Rb、Br部分取代Cs和I，在多原子竞争下，提高电子激发活性，再通过调控原子比例，形成梯度分布的Eg和多级态MEG阀值，进而有效利用多波段光子耦合作用，产生宽波区多级MEG。为实现该思想将重点研究：量子点微波可控合成与机理；原子比例与能带结构、MEG阀值间的联系；光生激子束缚与跃迁的动力学过程等。

本项目构建了多组元钙钛矿结构量子点，引入多种离子掺杂，通过调控原子比例，形成梯度分布的Eg和多级态MEG阀值，进而有效利用多波段光子耦合作用，产生宽波区多级MEG。本研究解释了钙钛矿结构量子点原子组成、能带结构和激子效率间的内在关系，解析多元量子点光生激子产生、分离和传输的超快动力学过程，揭示多级 MEG产生机制和热力学条件；通过调控原子比例和优化合成工艺，获得具有Eg梯度分布和多波段光子耦合效的量子点，最终建立一种高量子产率、宽波区多级MEG钙钛矿量子点合成技术。.在该项目资助下发表SCI学术论文49篇，其中影响因子超过10的20多篇，ESI高被引论文4篇。申请国家发明专利6项、实用新型专利1项，授权发明专利4项、实用新型专利1项。受邀参加了17个国内外学术会议，并做邀请报告。受邀赴瑞典隆德大学化学物理系、瑞典林雪萍大学、斯洛伐克科学院物理研究所和香港城市大学光子研究中心等做学术报告。项目资助下，培养了硕士、博士研究生12人，其中2人获得北京科技大学优秀博士学位论文。

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