Yao Zhaoyang, Zhang Fuguo, Guo Yaxiao, Wu Heng, He Lanlan, Liu Zhou, Cai Bin, Guo Yu, Brett Calvin J, Li Yuanyuan, Srambickal Chinmaya Venugopal, Yang Xichuan, Chen Gang, Widengren Jerker, Liu Dianyi, Gardner James M, Kloo Lars, Sun Licheng
Department of Chemistry, Zhejiang University, Hangzhou 310028, China.
School of Physical Science and Technology, ShanghaiTech University, Shanghai 201210, China.
J Am Chem Soc. 2020 Oct 14;142(41):17681-17692. doi: 10.1021/jacs.0c08352. Epub 2020 Oct 1.
Conjugated polymers are regarded as promising candidates for dopant-free hole-transport materials (HTMs) in efficient and stable perovskite solar cells (PSCs). Thus far, the vast majority of polymeric HTMs feature structurally complicated benzo[1,2-:4,5-']dithiophene (BDT) analogs and electron-withdrawing heterocycles, forming a strong donor-acceptor (D-A) structure. Herein, a new class of phenanthrocarbazole ()-based polymeric HTMs (, , and ) has been synthesized by inserting a unit into a polymeric thiophene or selenophene chain with the aim of enhancing the π-π stacking of adjacent polymer chains and also to efficiently interact with the perovskite surface through the broad and planar conjugated backbone of the . Suitable energy levels, excellent thermostability, and humidity resistivity together with remarkable photoelectric properties are obtained via meticulously tuning the conformation and elemental composition of the polymers. As a result, PSCs containing as dopant-free HTM show a stabilized power conversion efficiency (PCE) of 20.8% and significantly enhanced longevity, rendering one of the best types of PSCs based on dopant-free HTMs. Subsequent experimental and theoretical studies reveal that the planar conformation of the polymers contributes to an ordered and face-on stacking of the polymer chains. Furthermore, introduction of the "Lewis soft" selenium atom can passivate surface trap sites of perovskite films by Pb-Se interaction and facilitate the interfacial charge separation significantly. This work reveals the guiding principles for rational design of dopant-free polymeric HTMs and also inspires rational exploration of small molecular HTMs.
共轭聚合物被认为是高效稳定的钙钛矿太阳能电池（PSC）中无掺杂空穴传输材料（HTM）的有前途的候选材料。到目前为止，绝大多数聚合物HTM具有结构复杂的苯并[1,2 - :4,5 - ']二噻吩（BDT）类似物和吸电子杂环，形成强供体 - 受体（D - A）结构。在此，通过将 单元插入聚合物噻吩或硒吩链中，合成了一类新型的菲咯咔唑（ ）基聚合物HTM（ 、 和 ），目的是增强相邻聚合物链的π - π堆积，并通过 的宽平面共轭主链与钙钛矿表面有效相互作用。通过精心调整聚合物的构象和元素组成，获得了合适的能级、优异的热稳定性和耐湿性以及显著的光电性能。结果，含有 作为无掺杂HTM的PSC显示出20.8%的稳定功率转换效率（PCE）和显著提高的寿命，使其成为基于无掺杂HTM的最佳类型的PSC之一。随后的实验和理论研究表明，聚合物的平面构象有助于聚合物链的有序和面内堆积。此外，引入“路易斯软”硒原子可以通过Pb - Se相互作用钝化钙钛矿薄膜的表面陷阱位点，并显著促进界面电荷分离。这项工作揭示了无掺杂聚合物HTM合理设计的指导原则，也激发了对小分子HTM的合理探索。
