Engineering Research Center of Environment-Friendly Functional Materials, Ministry of Education, Institute of Materials Physical Chemistry, Huaqiao University, Xiamen, Fujian, 361021, China.
Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen, Guangdong, 518055, China.
Small. 2023 Jul;19(27):e2207784. doi: 10.1002/smll.202207784. Epub 2023 Mar 28.
Perovskite solar cells (PSCs) with n-i-p structures often utilize an organic 2,2',7,7'-tetrakis (N, N-di-p-methoxyphenyl-amine) 9,9'-spirobifluorene (spiro-OMeTAD) along with additives of lithium bis(trifluoromethanesulfonyl)imide salt (LiTFSI) and tert-butylpyridine as the hole transporting layer (HTL). However, the HTL lacks stability in ambient air, and numerous defects are often present on the perovskite surface, which is not conducive to a stable and efficient PSC. Therefore, constructive strategies that simultaneously stabilize spiro-OMeTAD and passivate the perovskite surface are required. In this work, it is demonstrated that a novel ionic liquid of dimethylammonium bis(trifluoromethanesulfonyl)imide (DMATFSI) could act as a bifunctional HTL modulator in n-i-p PSCs. The addition of DMATFSI into spiro-OMeTAD can effectively stabilize the oxidized spiro-OMeTAD cation radicals through the formation of spiro-OMeTAD TFSI because of the excellent charge delocalization of the conjugated CF SO moiety within TFSI . In addition, DMA cations could move toward the perovskite from the HTL, resulting in the passivation of defects at the perovskite surface. Accordingly, a power conversion efficiency of 23.22% is achieved for PSCs with DMATFSI and LiTFSI co-doped spiro-OMeTAD. Moreover, benefiting from the improved ion migration barrier and hydrophobicity of the HTL, still retained nearly 80% of their initial power conversion efficiency after 36 days of exposure to ambient air.
钙钛矿太阳能电池（PSCs）具有 n-i-p 结构，通常采用有机 2,2',7,7'-四（N,N-二-对甲氧基苯基-胺）9,9'-螺二芴（spiro-OMeTAD），并添加双（三氟甲烷磺酰基）亚胺锂盐（LiTFSI）和叔丁基吡啶作为空穴传输层（HTL）。然而，HTL 在环境空气中不稳定，并且钙钛矿表面通常存在许多缺陷，这不利于稳定和高效的 PSC。因此，需要构建同时稳定 spiro-OMeTAD 并钝化钙钛矿表面的策略。在这项工作中，证明了新型离子液体二甲基铵双（三氟甲烷磺酰基）亚胺（DMATFSI）可以作为 n-i-p PSCs 中的双功能 HTL 调节剂。DMATFSI 加入 spiro-OMeTAD 中可以通过形成 spiro-OMeTAD TFSI 有效地稳定氧化的 spiro-OMeTAD 阳离子自由基，因为 CF SO 部分在 TFSI 内的共轭电荷离域化效果很好。此外，DMA 阳离子可以从 HTL 向钙钛矿移动，从而钝化钙钛矿表面的缺陷。因此，具有 DMATFSI 和 LiTFSI 共掺杂 spiro-OMeTAD 的 PSCs 实现了 23.22%的功率转换效率。此外，由于 HTL 的离子迁移势垒和疏水性得到改善，在暴露于环境空气 36 天后，仍保留了近 80%的初始功率转换效率。
