Cobalt Oxide (CoOx) as an Efficient Hole-Extracting Layer for High-Performance Inverted Planar Perovskite Solar Cells

Ahmed Esmail Shalan; Tomoya Oshikiri; Sudhakar Narra; Mahmoud M Elshanawany; Kosei Ueno; Hui-Ping Wu; Keisuke Nakamura; Xu Shi; Eric Wei-Guang Diau; Hiroaki Misawa

doi:10.1021/acsami.6b10803

Cobalt Oxide (CoO_x) as an Efficient Hole-Extracting Layer for High-Performance Inverted Planar Perovskite Solar Cells

ACS Appl Mater Interfaces. 2016 Dec 14;8(49):33592-33600. doi: 10.1021/acsami.6b10803. Epub 2016 Nov 30.

Authors

Affiliations

¹ Research Institute for Electronic Science, Hokkaido University , N21, W10, Kita-ku, 001-0021, Sapporo, Japan.
² Department of Applied Chemistry & Institute of Molecular Science, National Chiao Tung University , 1001 Ta Hsueh Road, Hsinchu 30010, Taiwan.

PMID: 27960362
DOI: 10.1021/acsami.6b10803

Abstract

CoO_x is a promising hole-extracting layer (HEL) for inverted planar perovskite solar cells with device configuration ITO/CoO_x/CH₃NH₃PbI₃/PCBM/Ag. The devices fabricated according to a simple solution procedure showed the best photovoltaic performance attaining power conversion efficiency (PCE) of 14.5% under AM 1.5 G 1 sun irradiation, which is significantly superior to those of materials fabricated with a traditional HEL such as PEDOT:PSS (12.2%), NiO_x (10.2%), and CuO_x (9.4%) under the same experimental conditions. We characterized the chemical compositions with XPS, crystal structures with XRD, and film morphology with SEM/AFM techniques. Photoluminescence (PL) spectra and the corresponding PL decays for perovskite deposited on varied HEL films were recorded to obtain the hole-extracting characteristics, for which the hole-extracting times show the order CoO_x (2.8 ns) < PEDOT:PSS (17.5 ns) < NiO_x (22.8 ns) < CuO_x (208.5 ns), consistent with the trend of their photovoltaic performances. The reproducibility and enduring stability of those devices were examined to show the outstanding long-term stability of the devices made of metal oxide HEL, for which the CoO_x device retained PCE ≈ 12% for over 1000 h.

Keywords: cobalt oxide; hole-extraction layer; perovskite solar cell; photoluminescence; photovoltaic devices.