Quinoidal 2,2′,6,6′‐Tetraphenyl‐Dipyranylidene as a Dopant‐Free Hole‐Transport Material for Stable and Cost‐Effective Perovskite Solar Cells

We report on the use of 2,2′,6,6′‐tetraphenyldipyranylidene (DIPO‐Ph 4 ), a large quinoidal planar π‐conjugated heterocycle, as a simple, easy‐to‐synthetize, and efficient dopant‐free hole‐transport material in perovskite solar cells (PSCs). PSCs using pristine DIPO‐Ph 4 show photon conversion efficiencies up to 10.1 %, which is higher than a PSC utilizing dopant‐free spiro‐OMeTAD (5.1 %). DIPO‐Ph 4 ‐based PSCs exhibit a short‐circuit current density of 19.52 mA cm −2 and an open‐circuit voltage of 0.933 V, values that are superior to dopant‐free spiro‐OMeTAD and comparable to doped spiro‐OMeTAD. These better performances find their origin in a higher HOMO level (−4.74 eV) and a much higher hole mobility (2×10 −2  cm 2  V −1  s −1 ). Finally, PSCs based on DIPO‐Ph 4 possess a superior stability compared to doped‐spiro‐OMeTAD‐based devices when tested over 600 h.