钙钛矿/有机叠层太阳能电池及其动态光电特性研究

Perovskite solar cells have become the newest research hotspot due to their high efficiency and easy fabrication. Because of the limitation of the band gap (1.55 eV), methyl ammonium lead iodide solar cells cannot absorb light with longer wavelength than 800 nm and the absorption in the range from 600 to 800 nm is also relatively weak. How to broaden its absorption spectrum is the key issue to improve the efficiency further. Firstly, we propose the strategy of “perovskite/bulk-heterojunction” hybrid structure solar cell and “perovskite+bulk heterojunction” tandem solar cell. We expect to broaden the absorption spectrum of solar cells by combining the superb properties of perovskite and the advantage of organic materials to predict a higher efficiency; Three dimensional graphene structure is introduced as the electrode and it can increase the contact area with organic and (or) perovskite, which will solve the problems of ohmic contact and improve the carrier collection in solar cells. Secondly, the mechanism of the charge generation and the free carrier transportation in perovskite solar cells is still unclear, which is also an urgent problem to be solved. On the aspect of mechanism, we establish the temporal analysis to study the dynamic photoelectric property of the above solar cells which can realize the measurement from zero-dimension to one-dimension. We aim to measure the time from the moment of absorbing light to producing a stable current in solar cells. This measurement can help to study the process of the photoelectric conversion, carrier transportation and recombination in solar cells, so we can further reveal the working mechanism of perovskite and tandem solar cells.

钙钛矿型电池是当前太阳能电池研究的最新热点。但甲胺铅碘钙钛矿材料受自身带隙（1.55 eV）的限制不能有效利用波长大于800 nm的太阳光，并且在600-800 nm的吸收也相对较弱。如何扩展钙钛矿材料对太阳光的吸收成为进一步提升电池效率的关键。本项目首先将钙钛矿和有机材料相结合，制备“钙钛矿/有机体异质结”混合结构、“钙钛矿+有机体异质结”叠层结构太阳能电池，通过有机材料在长波段较强的吸收来弥补钙钛矿材料的吸收，并引入石墨烯三维结构作为电极，改善电池欧姆接触及载流子传输，最终提高电池的性能。其次，钙钛矿电池中自由电荷的产生和输运机制仍存在争议，也是亟需解决的重要问题。针对此问题，本项目采用“时间分析”方法研究所制备电池的动态光电特性，测量电池从接收光照到产生电流的时间，实现将零维测量变为一维测量来研究光电转换过程和载流子传输复合过程，进一步解释钙钛矿电池及钙钛矿/有机叠层电池的工作机制。

钙钛矿材料由于具有优异的光电性能，近年来被广泛研究。针对如何扩展活性层对太阳光的吸收能力从而进一步提升电池效率的关键问题，本项目提出了制备有机/钙钛矿叠层太阳能电池的方案，并从有机太阳能电池优化、钙钛矿电池优化、叠层电池制备三个方面开展相关研究，提升电池的性能。针对有机太阳能电池的优化，采用界面修饰、添加剂优化、三元策略、非富勒烯等提高了有机太阳能电池的性能，光电效率最高达到14.46%；优化手段包括两步法处理提高PEDOT:PSS光电特性以及采用离子型芳酸菁小分子作为阴极界面层，不同特性溶剂添加剂（DIO、CN、DPE等）对聚合物电池中分子结晶特性影响及器件性能最优化，采用双受体或双给体以及量子点掺杂等三元策略和改善器件性能，基于非富勒烯制备高性能有机太阳能电池等。针对钙钛矿太阳能电池性能的提升，从空穴传输层、钙钛矿层、电子传输层及阴极界面三个方面开展工作，实现了光电效率超过22%的钙钛矿太阳能电池；优化策略包括基于PEOz掺杂的PEDOT:PSS以及芳胺类小分子（NBNDD、TPASBP、NPB等）作为空穴传输层制备高效的p-i-n型器件，采用溶剂退火、添加剂掺杂的反溶剂法、有机阳离子调控、二元有机离子间协同等提高钙钛矿薄膜质量和器件性能，添加剂处理电子传输层PCBM以及采用聚电解质作为阴极界面修饰提高器件性能等。基于有机太阳能电池和钙钛矿太阳能电池的研究成果，我们对“钙钛矿/有机”混合薄膜电池以及有机/钙钛矿叠层太阳能电池进行了初步研究，提出了可行的中间连接层方案，制备了有机/钙钛矿叠层太阳能电池。本项目对于有机和钙钛矿太阳能电池的研究广泛深入，对于该领域的研究具有很好的参考和借鉴；同时有机/钙钛矿叠层电池的可行性得到论证，有利于相关研究的深入开展。