Keggin-Type PMo₁₁V as a P-type Dopant for Enhancing the Efficiency and Reproducibility of Perovskite Solar Cells

The conventional perovskite solar cells (PSCs) with 2,2′,7,7′-tetrakis( N, N -dimethoxyphenylamine)-9,9′-spirobifluorene (spiro-OMeTAD) as a hole transporting material commonly suffer from poor stability and reproducibility mainly due to the process of placing the devices in air and illumination for oxidizing the spiro-OMeTAD. Herein, Keggin-type polyoxometalates (POMs)-phosphovanadomolybdate (H 4 PMo 11 V·nH 2 O, denoted as PMo 11 V) is for the first time employed as a p-type dopant for promoting the oxidation of spiro-OMeTAD. Thereby, without illumination and air, the conductivity and hole extraction efficiency of the PMo 11 V doped spiro-OMeTAD with assistance of lithium bis(trifluoromethanesulfonyl)imide (Li-TFSI) and 4- tert -butylpyridine (TBP) can be dramatically enhanced. On the basis of this strategy, the corresponding PSCs exhibit substantially improved photovoltaic performance and good reproducibility. The best performing device yields a power conversion efficiency (PCE) of 14.05%. This work indicates a great potential of polyoxometalates for further applications in solar cells and other optoelectronics devices.