Efficient and Stable Perovskite Solar Cells Using Molybdenum Tris(dithiolene)s as p‑Dopants for Spiro-OMeTAD

Metal halide perovskite solar cells have now reached efficiencies of over 22%. To date, the most efficient perovskite solar cells have the n-i-p device architecture and use 2,2′,7,7′-tetrakis­(<i>N,N</i>′-di-<i>p</i>-methoxyphenylamine)-9,9′-spirobifluorene or poly­(triarylamine) as the hole transport material (HTM), which are typically doped with lithium bis­((trifluomethyl)­sulfonyl)­amide (Li-TFSI). Li-TFSI is hygroscopic and detrimental to the long-term performance of the solar cells, limiting its practical use. In this work, we successfully replace Li-TFSI by molybdenum tris­(1-(methoxycarbonyl)-2-(trifluoromethyl)­ethane-1,2-dithiolene), Mo­(tfd-CO₂Me)₃, or molybdenum tris­(1-(trifluoroacetyl)-2-(trifluoromethyl)­ethane-1,2-dithiolene), Mo­(tfd-COCF₃)₃. With these two dopants, we achieve stabilized power conversion efficiencies up to 16.7% and 15.7% with average efficiencies of 14.8% ± 1.1% and 14.4% ± 1.2%, respectively. Moreover, we observe a significant enhancement of the long-term stability of perovskite solar cells under 85 °C thermal stressing in air