Single-Walled Carbon Nanotube Film as Electrode in Indium-Free Planar Heterojunction Perovskite Solar Cells: Investigation of Electron-Blocking Layers and Dopants

• Published in: Nano letters Vol. 15; no. 10; pp. 6665 - 6671
• Main Authors: Jeon, Il, Chiba, Takaaki, Delacou, Clement, Guo, Yunlong, Kaskela, Antti, Reynaud, Olivier, Kauppinen, Esko I, Maruyama, Shigeo, Matsuo, Yutaka
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 14.10.2015
• Subjects: Devices; Doping; Perovskites; Photovoltaic cells; Polyethylene terephthalates; Single wall carbon nanotubes; Solar cells; Wettability; PEDOT:PSS modification; carbon nanotube; perovskite solar cell; flexible solar cell; ITO-free; MoO3 doping
• ISSN: 1530-6984; 1530-6992
• DOI: 10.1021/acs.nanolett.5b02490

In this work, we fabricated indium-free perovskite solar cells (SCs) using direct- and dry-transferred aerosol single-walled carbon nanotubes (SWNTs). We investigated diverse methodologies to solve SWNTs’ hydrophobicity and doping issues in SC devices. These include changing wettability of poly­(3,4-ethylenedioxythiophene)/poly­(styrenesulfonate) (PEDOT:PSS), MoO3 thermal doping, and HNO3(aq) doping with various dilutions from 15 to 70 v/v% to minimize its instability and toxic nature. We discovered that isopropanol (IPA) modified PEDOT:PSS works better than surfactant modified PEDOT:PSS as an electron-blocking layer on SWNTs in perovskite SCs due to superior wettability, whereas MoO3 is not compatible owing to energy level mismatching. Diluted HNO3 (35 v/v%)-doped SWNT-based device produced the highest PCE of 6.32% among SWNT-based perovskite SCs, which is 70% of an indium tin oxide (ITO)-based device (9.05%). Its flexible application showed a PCE of 5.38% on polyethylene terephthalate (PET) substrate.