Dopant Engineering for Spiro‐OMeTAD Hole‐Transporting Materials towards Efficient Perovskite Solar Cells
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Abstract
<jats:title>Abstract</jats:title><jats:p>One of the most prominent hole‐transporting material (HTM) for hybrid perovskite solar cells has been 2,2″,7,7″‐tetrakis[<jats:italic>N</jats:italic>,<jats:italic>N</jats:italic>‐di(4‐methoxyphenyl)amino]‐9,9′‐spirobifluorene (spiro‐OMeTAD), which is commonly doped with metal bis(trifluoromethylsulfonyl)imide (M(TFSI)<jats:italic><jats:sub>n</jats:sub></jats:italic>) salts that contribute to generating the active radical cation HTM species. The underlying role of the metal cation, however, remains elusive. Here, the effect of metal cations (M = Li, Zn, Ca, Cu, and Sc) on doping spiro‐OMeTAD is analyzed by a combination of techniques, including electron paramagnetic resonance spectroscopy and cyclic voltammetry, which is complemented by photovoltaic device and hole mobility analysis. As a result, the authors reveal the superiority of Zn(TFSI)<jats:sub>2</jats:sub> salts in device performances as compared to the others, including redox‐active Cu(TFSI)<jats:sub>2</jats:sub>. This analysis thereby unravels new design principles for dopant engineering in HTMs for hybrid perovskite photovoltaics.</jats:p>