Ionic liquid dopant for hole transporting layer towards efficient LiTFSI-free perovskite solar cells

• Published in: Chemical physics letters Vol. 801; p. 139713
• Main Authors: Zhu, Hao, Mo, Yanping, Wang, Chao, Li, Jing, Tian, Congcong, Wen, Yongtao, Lin, Zhipeng, Yu, Guomu, Wang, Luqi, Hou, Peiran, Zhang, Xiao-Li, Li, Wei, Cheng, Yi-Bing, Huang, Fuzhi
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 16.08.2022
• Subjects: Dopants; Ionic liquid; LiTFSI-free; Perovskite solar cells; Spiro-OMeTAD; LiTFSI-free; Dopants; Spiro-OMeTAD; Perovskite solar cells; Ionic liquid
• ISSN: 0009-2614; 1873-4448
• DOI: 10.1016/j.cplett.2022.139713

[Display omitted] •A novel ionic liquid namely BMPIP-TFSI was used as dopant to replace Li-TFSI.•The device based on ionic liquid dopant has a best PCE of 23.01%.•The device based on ionic liquid retaining 85% of its initial efficiency after 500 h stored under humid environment. Regarded as one of the best hole transporting material (HTM) for perovskite solar cells, 2,2′,7,7′-tetrakis-(N,N-di-4-methoxyphenylamino)-9,9′-spirobifluorene (spiro-OMeTAD) has suffered from instability induced by Lithium bis(trifluoromethanesulfonyl)imide (Li-TFSI) hygroscopicity and aggregation. Herein, we replace Li-TFSI with the hydrophobic ionic liquid (IL) 1-Butyl-1-methylpiperidinium bis(trifluoromethyl sulfonyl)imide (BMPIP-TFSI). The BMPIP-TFSI functions as a p-type dopant in the spiro-OMeTAD, increasing the hole mobility, promoting the conductivity and enhancing the moisture-resistance of HTM. The corresponding perovskite solar cells achieve a champion power conversion efficiency exceeding 23%. Furthermore, the un-encapsulated devices show enhanced stability under humid environment, retaining 85% of its initial efficiency after 500 h.