Fabrication of uniform electron transport layer on textured transparent conducting film using polyelectrolyte and colloidal particles and its application to perovskite solar cells
Ryo Ishikawa a, Hajime Shirai a
a Saitama University, 255 Shimo-Okubo, Sakura, Saitama, 338, Japan
Asia-Pacific International Conference on Perovskite, Organic Photovoltaics and Optoelectronics
Proceedings of Asia-Pacific International Conference on Perovskite, Organic Photovoltaics and Optoelectronics (IPEROP23)
Kobe, Japan, 2023 January 22nd - 24th
Organizers: Seigo Ito, Hideo Ohkita and Atsushi Wakamiya
Oral, Ryo Ishikawa, presentation 030
DOI: https://doi.org/10.29363/nanoge.iperop.2023.030
Publication date: 21st November 2022

Perovskite solar cells (PSCs) using organic-inorganic halides as a light-absorbing layer exhibit high power conversion efficiencies (PCEs; 25.7%) in small-area solar cells . The film quality dramatically affects the performance of PSCs and depends on the fine structure of the perovskite layers, including the crystallinity, surface coverage, and roughness. Also, Device structure dramatically affects performance, and the use of transparent conductive films with textured structures with light confinement effects effectively improves short-circuit current density. However, it is difficult to form a uniform electron transport layer on a textured structure using a solution method such as spin coating. The spray and chemical bath deposition methods can deposit films on textured structures without defects, but they require high temperatures or long deposition times.

In this study, a uniform electron transport layer was formed on a textured transparent conductive film by the sequential spin casting of positively charged Poly(9,9-bis(3'-(N,N-dimethylamino)propyl)-2,7-fluorene)-alt-2,7-(9,9-dioctylfluorene)](PFN) and negatively charged colloidal SnO2 solution, which is applied to perovskite solar cells.

 Uncoated areas were observed around the convexity without PFNs, whereas the SnO2 coverage increased with PFN. This is thought to be due to the electrostatic effect between PFN and SnO2 during deposition. FA1-xCsxPbI3 perovskite thin films were deposited on the electron transport layer using high-boiling co-solvent and Lewis bases as additives in a one-step process and without an antisolvent t[1~3]. Spiro-OMeTAD hole transport layer was deposited by spin-coating method, and finally an Ag electrode was formed by vacuum evaporation. The PCE of perovskite solar cells with a single SnO2 electron transport layer is 16.2% (13.0%) with JSC = 25.7 (25.7) mA·cm-2, VOC = 0.951 (0.874) V, and FF of 65.7% (57.9%) for the RS (FS),whereas the PFN/SnO2 bilayerd electron transport layer improves all performance factors, resulting in a PCE of 20.5% (20.0%) with JSC = 26.3 (26.4) mA·cm-2, VOC = 1.03(1.03) V, and FF of 75.5% (73.9%) for the RS (FS).

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