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  • Cobalt dopant with deep redox potential for organometal halide hybrid solar cells.

Cobalt dopant with deep redox potential for organometal halide hybrid solar cells.

ChemSusChem (2014-05-23)
Teck Ming Koh, Sabba Dharani, Hairong Li, Rajiv Ramanujam Prabhakar, Nripan Mathews, Andrew C Grimsdale, Subodh G Mhaisalkar
ABSTRACT

In this work, we report a new cobalt(III) complex, tris[2-(1H-pyrazol-1-yl)pyrimidine]cobalt(III) tris[bis(trifluoromethylsulfonyl)imide] (MY11), with deep redox potential (1.27 V vs NHE) as dopant for 2,2',7,7'-tetrakis-(N,N-di-p-methoxyphenylamine)-9,9'-spirobifluorene (spiro-OMeTAD). This dopant possesses, to the best of our knowledge, the deepest redox potential among all cobalt-based dopants used in solar cell applications, allowing it to dope a wide range of hole-conductors. We demonstrate the tuning of redox potential of the Co dopant by incorporating pyrimidine moiety in the ligand. We characterize the optical and electrochemical properties of the newly synthesized dopant and show impressive spiro-to-spiro(+) conversion. Lastly, we fabricate high efficiency perovskite-based solar cells using MY11 as dopant for molecular hole-conductor, spiro-OMeTAD, to reveal the impact of this dopant in photovoltaic performance. An overall power conversion efficiency of 12% is achieved using MY11 as p-type dopant to spiro-OMeTAD.

MATERIALS
Product Number
Brand
Product Description

Sigma-Aldrich
FK 209 Co(II) TFSI salt
Sigma-Aldrich
FK 209 Co(III) TFSI salt
Sigma-Aldrich
FK 209 Co(III) PF6 salt
Sigma-Aldrich
FK 102 Co(II) PF6 salt
Sigma-Aldrich
FK 102 Co(III) PF6 salt