利用同步辐射技术研究新型钙钛矿/富勒烯异质结太阳能电池的稳定性

The conversion efficiency of perovskite solar cell (PSC) has reached 20%, which makes it the most promising candidate to substitute the commercialized silicon solar cells. However, the stability is a key problem to be resolved, which determines the commercial application of PSCs. In order to improve the stability of PSCs, in this proposal, we’d like to study the possibility of fullerenes serving as an electron acceptor, to transport electrons and stabilize perovskite structure simultaneously. 1) Firstly, we’d like to synthesize a series of fullerene derivatives electron acceptors which can also be used to stabilize perovskite structure. Then, perovskite/fullerene bulk heterojunction cells will be prepared, to optimize the stability and performance of PSCs by controlling the structure of derivatives, the doping proportion of derivatives in perovskite and processing method of heterojunction. 2) The most important is that XANES is applied to study the interactions between groups of fullerene derivatives and perovskite, their effect on the stability of perovskite, variation with time, relationship with conversion efficiency and the effect of other trace elements on stability. By GIXRD, the long-term stability of the structure of perovskite/fullerene films will be studied. Stabilizing perovskite structure by taking advantage of diversity of fullerene derivatives might provide experimental dates and theoretical guidance in solving the stability of PSCs.

钙钛矿太阳能电池已达到20%的转化效率，是硅太阳能电池强有力的对手，但稳定性是急需解决的关键问题，决定着钙钛矿电池的商业化应用。本项目针对这一问题，结合本实验室富勒烯及太阳能电池的研究经验，及富勒烯可作为电子受体并起到电子传输的同时稳定钙钛矿结构的可能性，1）合成一系列能稳定钙钛矿结构的富勒烯衍生物电子受体，制备钙钛矿/富勒烯体异质结电池，通过控制衍生物的结构，与钙钛矿的掺杂比例，及异质结的制备方法，优化电池的稳定性及器件性能。2）研究过程中，着重利用GIXRD及X射线近边吸收谱，研究富勒烯衍生物引入的基团与钙钛矿的相互作用，对钙钛矿稳定性的影响，随时间的变化规律，及与光电转化效率之间关系，发现其他微量元素对稳定性的影响，研究含有不同富勒烯衍生物的钙钛矿/富勒烯膜长期放置过程中深层次结构的变化，从而利用富勒烯衍生物的多样性找到稳定钙钛矿结构的方法，为解决稳定性问题提供实验依据和理论指导。

本项目的研究目标是利用同步辐射技术研究钙钛矿电池稳定性。到目前为止，工作进展顺利，实现并超过了预期目标，已发表SCI论文10篇，最高影响因子12.12，申请及授权专利2项，培养博士及硕士5人。.研究期间，制备了多种富勒烯及金属富勒烯衍生物，对材料的结构性质等进行表征，并制备了多种富勒烯掺杂的钙钛矿电池，研究了钙钛矿电池在不同光照，不同温度，不同湿度条件下的稳定性，揭示了影响稳定性的因素。.特别值得一提的是，我们通过掺杂适当比例PCBM，不仅提高了电池的效率， 而且提高了其在光，温度，湿度等条件下的稳定性。而且，利用掠入射X射线衍射技术(GIXRD)及X射线近边吸收谱研究发现，PCBM提高稳定性及电池效率的原因在于PCBM可以诱导Pb2+向高价态Pb变化，从而有利于载流子的迁移以及更强的Pb—I键。这是首次揭示了PCBM提高电池效率及稳定性的机理。在此机理指导下，我们将Pb4+掺杂进入钙钛矿电池中，不仅提高了钙钛矿电池的稳定性， 而且使效率提高了55.8%。同步辐射技术在这一系列成果中起到无法替代的作用。